CN107708201B

CN107708201B - Positioning system and method of linear frequency modulation continuous wave based on label difference frequency forwarding

Info

Publication number: CN107708201B
Application number: CN201710717835.2A
Authority: CN
Inventors: 陈祝明; 徐聪; 王毅; 伯巍; 王子晟
Original assignee: University of Electronic Science and Technology of China
Current assignee: Hefei Sixianzhi New Technology Co ltd
Priority date: 2017-08-21
Filing date: 2017-08-21
Publication date: 2020-03-20
Anticipated expiration: 2037-08-21
Also published as: CN107708201A

Abstract

The invention discloses a positioning system and a positioning method of linear frequency modulation continuous waves based on label difference frequency forwarding, which comprise a main control module, M base stations and N labels to be positioned, wherein the main control module is used for generating LFMCW signals and reference signals of the whole system and transmitting the LFMCW signals and the reference signals to the base stations, receiving and processing forwarding signals from the base stations, and calculating the position information of the labels to be positioned according to the processed forwarding signals; the base station is used for receiving the LFMCW signal and the reference signal transmitted by the main control module, transmitting the processed LFMCW signal to the label to be positioned, receiving and processing a forwarding signal from the label to be positioned, and transmitting the processed forwarding signal to the main control module; the base station performs frequency mixing processing when processing both LFMCW signals and forwarding signals, and the reference signal is used as a reference source when a local oscillator signal used for frequency mixing processing is generated; the label to be positioned is used for receiving and transmitting LFMCW signals from the base station by difference frequency. The invention can realize accurate synchronous control among the main control module, the base station and the label to be positioned.

Description

Positioning system and method of linear frequency modulation continuous wave based on label difference frequency forwarding

Technical Field

The invention relates to an indoor positioning technology, in particular to a system and a method for positioning linear frequency modulation continuous waves based on label difference frequency forwarding.

Background

In recent years, with the rise of the internet of things, researchers are receiving more and more attention to area location technologies based on wireless sensor networks, wireless local area networks and the like. Indoor location technologies in buildings such as supermarkets, shopping malls, museums, hospitals and communities have also developed rapidly. In the current indoor positioning technology, a positioning scheme based on a linear frequency modulation continuous wave signal (LFMCW) system has a strong multipath effect resistance, high positioning accuracy and strong indoor penetration capability due to the fact that signals of the positioning scheme have large bandwidth of hundreds of megameters, and therefore the positioning scheme has a wide application prospect.

Most of the existing positioning schemes based on the LFMCW system are based on a ranging algorithm, a transmitting signal and a receiving signal are subjected to beat processing by utilizing the characteristic that the frequency of an LFMCW signal changes linearly along with time, a difference frequency item is extracted to further calculate the distance between a positioning label and a transmitting base station, and finally the position of the label to be positioned is determined by adopting a hyperbolic positioning algorithm or a circular positioning algorithm.

Chinese patent publication No. CN104133191A discloses a self-rephotograph receiving tag. And obtaining the distance difference from the signal transmitting base station to the tag through the frequency difference of the received signals of the base stations. The structure of transmitting LFMCW signals to the tag through two base stations each time and calculating the frequency difference requires strict synchronization between the base stations to ensure the real-time performance and high precision of indoor positioning.

Chinese patent publication No. CN103558598A discloses that positioning is achieved by A, B two devices sending LFMCW signals to each other and then extracting the frequency difference between the transmitted signal and the received signal to calculate the distance between A, B. In the scheme, A, B two devices respectively transmit LFMCW signals, timing devices at the transmitting end and the receiving end are difficult to maintain consistency due to the existence of time difference of crystal oscillator sources, and if the crystal oscillator sources with ultra-high precision are adopted, the price is very high, so that the implementation performance of the whole scheme is poor.

Disclosure of Invention

The invention aims to provide a positioning system and a positioning method of linear frequency modulation continuous waves based on label difference frequency forwarding, so as to solve the problem of poor real-time performance caused by the fact that a base station, a main control module and labels cannot be accurately and synchronously controlled in the prior positioning technology.

The invention is realized by the following technical scheme: the positioning system of the linear frequency modulation continuous wave based on label difference frequency forwarding comprises a main control module, M base stations and N labels to be positioned, wherein M is a natural number not less than 3, M base stations are not collinear and have known positions, and N is a natural number not less than 1; the main control module is used for generating LFMCW signals and reference signals of the whole system, transmitting the LFMCW signals and the reference signals to the base station, receiving and processing forwarding signals from the base station, and resolving the position information of the label to be positioned according to the processed forwarding signals; the base station is used for receiving the LFMCW signal and the reference signal transmitted by the main control module, processing the LFMCW signal, transmitting the processed LFMCW signal to the label to be positioned, receiving and processing a forwarding signal from the label to be positioned, and transmitting the processed forwarding signal to the main control module; the base station performs frequency mixing processing when processing both LFMCW signals and forwarding signals, and the reference signal is used as a reference source when a local oscillator signal used in the frequency mixing processing is generated; the label to be positioned is used for receiving and transmitting LFMCW signals from the base station by difference frequency.

The ideal indoor positioning scheme not only needs to meet the characteristics of high precision and wide range, but also needs to have the requirements of real-time performance, high stability, low cost and easy implementation. In a positioning scheme in the prior art, for example, patent CN104133191A discloses a self-heterodyne receiving tag, which obtains a distance difference from a signal transmitting base station to the tag through a frequency difference of received base station signals, but in a structure that LFMCW signals are transmitted to the tag through two base stations each time and the frequency difference is calculated, strict synchronization between the base stations is required to ensure real-time performance and high-precision requirements of indoor positioning; patent CN103558598A discloses that positioning is achieved by sending LFMCW signals to each other by A, B two devices, and then extracting the frequency difference between the transmitted signal and the received signal to calculate the distance between A, B, in this scheme, A, B two devices each transmit LFMCW signals, because there is a time difference between the crystal oscillator sources, it is difficult to maintain consistency between the timing devices at the transmitting end and the receiving end, and if the crystal oscillator sources with ultra-high precision are adopted as mentioned in this scheme, the price is very expensive, resulting in poor implementation of the whole scheme. Therefore, the positioning scheme in the prior art has the problem of poor real-time performance caused by the fact that the base station, the main control module and the labels cannot be accurately and synchronously controlled, and the implementation performance of the scheme is poor due to the fact that the system cost is increased in order to improve the accuracy.

In order to solve the problems in the prior art, the invention provides a positioning system of a linear frequency modulation continuous wave based on label difference frequency forwarding. The positioning system comprises a main control module, M base stations and N labels to be positioned, wherein M is a natural number not less than 3, the M base stations are not collinear and have known positions, N is a natural number not less than 1, namely the number of the base stations is at least 3, and the number of the labels to be positioned is at least 1. Preferably, the number of the base stations can be set to be more than 4 in consideration of the redundancy of the system and the signal shielding of the tag to be positioned, namely M is more than or equal to 4. When the device is used, the main control module firstly generates a reference signal, the reference signal is used as a reference source to generate an LFMCW signal, then the reference signal and the LFMCW signal are sent to M base stations, the M base stations process the LFMCW signal after receiving the reference signal and the LFMCW signal and send the LFMCW signal to a label to be positioned, the label to be positioned receives the signal from each base station and processes the signal and transmits the signal back to each base station, each base station receives a forwarding signal from the label to be positioned and then processes the signal and transmits the signal to the main control module, and the main control module receives the forwarding signal returned by each base station and performs beat deskew, frequency conversion and resolving to obtain the position information of the label to be positioned.

After receiving and processing the signals from each base station, the label to be positioned forwards the signals to each base station, and the label to be positioned is essentially a difference frequency repeater, so that synchronous control with each base station is not needed. Meanwhile, the LFMCW signal and the reference signal generated by the main control module are both from the clock source in the main control module, i.e. the main control module and each base station only adopt one clock source, forming a coherent system, and therefore, synchronous control between each base station is not required. Through the arrangement, accurate synchronous control among the main control module, the base station and the label to be positioned can be realized, the cost is low, and the implementation of the positioning scheme is good.

In the technical scheme, the reference signal and the LFMCW signal generated by the main control module adopt the same clock source in the main control module to form a coherent system, and the random frequency deviation influencing the positioning precision of the system is avoided, so that synchronous control among base stations is not needed; the label to be positioned is not required to be provided with a clock source, and is essentially a differential frequency repeater, so that synchronous control with a base station is not required. Through the arrangement, the positioning system with high synchronization rate and low cost can be established by combining the characteristic that the frequency of the LFMCW signal changes linearly along with time.

Further, the label to be positioned comprises a differential rotation module, a communication module B and a power supply module; the difference conversion module is used for receiving the LFMCW signal from the base station, mixing the LFMCW signal and transmitting the mixed LFMCW signal to the base station, so that difference frequency is generated between the frequency of the signal received and transmitted to the base station; the communication module B is used for communicating with the main control module, and the main control module can schedule the label to be positioned; the power module is used for supplying power for the differential conversion module, and the power module further comprises a control module which is connected with the communication module B and used for receiving and returning instructions of the main control module. In the scheme, the difference conversion module is used for generating difference frequency between the frequencies received and transmitted to the base stations and transmitting the signals generating the difference frequency to each base station. The communication module B is used for communicating with the main control module, so that the main control module can schedule the label to be positioned, and the label to be positioned can receive the scheduling from the main control module; the power module is divided into a power supply part and a control module part, wherein the control module is connected with the communication module B, so that the power module can provide a controllable power supply for the differential conversion module. Before positioning begins, after a communication module B receives a positioning instruction from a main control module, a power supply module is started to supply power to a label to be positioned, and the label to be positioned is ready to be forwarded; after positioning is completed, the main control module sends an ending instruction to the communication module B of the tag to be positioned, and the tag to be positioned turns off the power supply module after receiving the instruction. Through the arrangement, the purpose of reducing the operation cost of the positioning system can be further achieved.

Further, the difference conversion module comprises an antenna B1, a band-pass filter D1, a low noise amplifier B, a mixer C, a band-pass filter D2, a power amplifier C and an antenna B2 which are connected in sequence, and the mixer C is connected with a frequency synthesizer C. In this scheme, antenna B1 is used to receive signals from each base station, and antenna B2 forwards LFMCW signals to the base stations. Preferably, the tag to be positioned can increase the positioning range of the system by increasing the transmission power. The band-pass filter D1 and the band-pass filter D2 are used for filtering signals, and the tag to be positioned can obtain good receiving and transmitting isolation degree through the band-pass filters connected with the two antennas, so that the good receiving and transmitting isolation degree can be obtained. The frequency synthesizer is a frequency synthesizer, and the frequency synthesizer C is a local oscillator of the label to be positioned and is used for generating local oscillation signals required by the frequency mixer C. The signal flow direction is as follows: after receiving the LFMCW signal from the base station, the antenna B1 is filtered by the band pass filter D1 and amplified by the low noise amplifier B, then the difference frequency is performed by the mixer C, and then the difference frequency is filtered by the band pass filter D2 and amplified by the power amplifier C, and finally the signal is forwarded by the antenna B2. Therefore, the difference conversion module does not add a clock source, and only forwards the signal from the base station to the base station after the signal difference frequency processing. The frequency synthesizer C of the label to be positioned has a certain random deviation relative to the main control module and the base station, but the hyperbolic positioning method of distance difference is adopted to eliminate the random deviation when the distance difference is measured between every two base stations, so that the positioning precision of the positioning system is not influenced.

Furthermore, the main control module comprises a clock source, a communication module a, a digital signal processing module, a frequency synthesizer A, LFMCW generation module and a synthesizer/distributor which are connected in sequence, wherein the output end of the synthesizer/distributor is simultaneously connected with at least M band-pass filters a, and the clock source is connected with the digital signal processing module and the frequency synthesizer a; the main control module further comprises at least M signal receiving units, each signal receiving unit comprises an A/D module A, a power amplifier A, a low-pass filter A, a frequency mixer A and a band-pass filter B which are sequentially connected, and the A/D module A is connected with the digital signal processing module; the frequency synthesizer A is also simultaneously connected with the synthesizer/distributor and the mixers A of all the signal receiving units; and the output end of the band-pass filter A and the input end of the band-pass filter B are connected with the base station. The frequency synthesizer A can generate a signal with stable frequency to serve as a coherent reference signal of the whole system, and the LFMCW generation module generates an LFMCW signal; the synthesis/distributor firstly synthesizes the reference signal and the LFMCW signal into a path of signal and then redistributes the signal into M paths of signals leading to M base stations; the band-pass filter A and the band-pass filter B can filter the signals to obtain signals of a required frequency band; the mixer A carries out down-conversion processing on a signal transmitted back by the base station; the power amplifier A amplifies the signal; the A/D module A samples and converts the signal into a digital signal; the digital signal processing module has the functions of digital signal processing and scheduling control for controlling the whole system; the communication module A is responsible for communication with the label to be positioned; the A/D module A and the communication module A are respectively connected with the digital signal processing module, and the communication module A is used for communicating with the label to be positioned to realize the scheduling function.

When the main control module initiates a positioning process, the generated and output signal flow direction is as follows in sequence: digital signal processing module, communication module A, frequency synthesizer A, LFMCW generation module, synthesizer/distributor 1, band-pass filter A, base station. Specifically, firstly, a digital signal processing module in a main control module informs a tag to be positioned of readiness through a communication module a, then the digital signal processing module controls a frequency synthesizer a to generate a reference frequency source signal, namely a reference signal, then controls an LFMCW generation module to generate an LFMCW signal by taking the reference signal as a reference source, then synthesizes the LFMCW signal and the reference signal into one path of signal through a synthesis/distributor, redistributes the signal into M paths of signals leading to M base stations, and transmits the signals to the M base stations after being filtered by band pass filters a of the paths.

The main control module receives and processes input signals of each base station, and the signal flow direction of the main control module is as follows in sequence: the base station, the band-pass filter B, the mixer A, the low-pass filter A, the power amplifier A, A/D module A and the digital signal processing module. After M processed signals in the base station are input to the main control module, the signals are firstly converted to lower frequency through the frequency mixers A of all paths to reduce the sampling rate required by the conversion of the A/D module A, then the signals are sent to the A/D module A to be converted into digital signals after being filtered by the low-pass filter A and amplified by the power amplifier A, and the digital signals are processed and resolved by the digital signal processing module to finally obtain the position information of the label to be positioned.

Further, each base station has the same internal structure, and the base station comprises a band-pass filter C2, a mixer B1, a band-pass filter C3, a power divider B, a power amplifier B1 and an antenna A1 which are connected in sequence; the base station further comprises a power amplifier B3, a band-pass filter C6, a mixer B3, a band-pass filter C5, a mixer B2, a low-noise amplifier A, a band-pass filter C4 and an antenna A2 which are connected in sequence, and the power divider B is connected with the mixer B2; the base station also comprises a band-pass filter C1, wherein the band-pass filter C1 is connected with a frequency synthesizer B, and the frequency synthesizer B is connected with a mixer B1 and a mixer B3. The M base stations all have the same internal structure, namely, the modules of each base station have the same connection relation. The antenna A1 is used for transmitting LFMCW signals of a certain frequency band, the antenna A2 is connected with the band-pass filter C4 and is used for receiving LFMCW signals which are forwarded by the difference frequency of the tag to be positioned and have another frequency band different from the transmitting frequency band, so that the system has good transmitting and receiving isolation, and preferably, the base station can increase the positioning range of the system by increasing the transmitting power. In the prior art, for example, in the positioning method disclosed in CN10413319A, the local oscillator signal is provided by amplifying the radio frequency signal received through the antenna, so the dynamic range of the local oscillator signal is relatively large, and when the signal power is small, it is difficult to ensure stable operation of the mixer. The band-pass filter C1 of the base station is connected with the frequency synthesizer B, and is used for filtering out a reference signal from a signal from the main control module, the reference signal is used as a reference source of a signal generated by the frequency synthesizer B, the frequency synthesizer B is used for generating a stable signal as a first local oscillation signal of the mixer B1, and the frequency synthesizer B also generates another second local oscillation signal as a mixer B3, so that the stable operation of each mixer can be ensured. The band-pass filter C2 is used to filter the LFMCW signal from the main control module, then the signal is up-converted in the mixer B1, filtered by the band-pass filter C3, and then divided into two paths by the power divider B, one path of signal is amplified by the power amplifier B1 and transmitted through the antenna a1, and the other path of signal is used as the local oscillator input signal of the mixer B2 of the receiving part of the base station. And the antenna A2 is connected with the band-pass filter C4 and is used for receiving the LFMCW signal of the other frequency band forwarded by the label to be positioned. And the mixer B2 is connected with the band-pass filter C5 and is used for deskewing the LFMCW signal forwarded by the tag to be positioned and the LFMCW signal beat originally transmitted by the base station. The mixer B3 is connected to a band pass filter C6 for down converting the beat signal for transmission back to the master control module.

Specifically, the signal flow of the base station transmitting signal is: the band-pass filter C1 and the band-pass filter C2 respectively filter out a reference signal and an LFMCW signal in a synthesized signal from the main control module, the frequency synthesizer B generates a first local oscillator signal and a second local oscillator signal by taking the reference signal as a frequency reference, the LFMCW signal and the first local oscillator signal enter a frequency mixer B1 for frequency conversion processing, then the LFMCW signal and the first local oscillator signal are filtered by the band-pass filter C3, amplified by a power amplifier B1, and finally transmitted to a positioning area through an antenna A1.

The signal flow direction forwarded by the base station receiving the label to be positioned is as follows: an LFMCW signal of a forwarding frequency band of a tag to be positioned is received by an antenna A2 and a band-pass filter C4, the LFMCW signal passes through a low-noise amplifier A, then beat and deskew processing is carried out on the LFMCW signal in a mixer B2, the LFMCW signal is subjected to frequency conversion in a mixer B3 and filtering in a band-pass filter C6 after being filtered by a band-pass filter C5 and amplified by a power amplifier B2, and finally the LFMCW signal is transmitted back to the main control module through a power amplifier B3.

Further, the reference signal is a single frequency signal, and the frequency of the reference signal is not included in the frequency range of the LFMCW signal. The purpose of the above arrangement is that after the signal is transmitted to the base station, the filtering separation can be performed by using the band-pass filters of different pass band ranges of different base stations.

Further, the starting frequencies of the signals transmitted to the tag to be positioned by different base stations are different. In the existing indoor positioning scheme based on frequency modulation continuous waves, devices for receiving and transmitting LFMCW signals, such as tags to be positioned and base stations, do not distinguish receiving frequency bands, and most devices select one frequency band, such as a 2.4G frequency band, for transmission, so that good receiving and transmitting isolation cannot be guaranteed. In order to solve the above problems, in the positioning system, the starting frequencies of signals transmitted to the tag to be positioned by different base stations are different, that is, when the LFMCW signal output by the band pass filter C2 is up-converted, the frequency synthesizer B generates different first local oscillation signals for the mixer B1 according to different base stations, so that the LFMCW signal transmitted to the tag to be positioned by each base station has a certain starting frequency difference, and thus, when the signal transmitted back by the tag to be positioned by each base station and the original transmission signal are subjected to beat deskew, the band pass filter C5 is used to distinguish whether the forwarded signal is transmitted to the tag to be positioned by the base station, thereby preventing signals from other base stations forwarded by the tag to be positioned from reaching the base station and forming mutual interference between the base stations.

Furthermore, signals are transmitted between the main control module and the base station through a television cable. The closed circuit television cable is adopted to realize the signal transmission between the main control module and the base station, so that the anti-interference performance of the system signal transmission is enhanced, the realization cost is low, and the cost performance of the whole indoor positioning system is improved. Specifically, after a reference signal generated in the main control module and a synthesized signal of the LFMCW are distributed into M paths by a synthesizer/distributor, the M paths are filtered by band-pass filters a of the respective paths, and are transmitted to M base stations through M paths of closed-circuit television cables, and meanwhile, the main control module also receives signals from the respective base stations through the closed-circuit television cables; in the base station, the base station can receive the synthesized signal from the main control module through a television cable, and simultaneously, the intermediate frequency signal of the signal which is subjected to beat deskew and frequency conversion in the base station to a television frequency band can be input to the main control module through the television cable.

The invention also discloses a positioning method of the linear frequency modulation continuous wave based on the label difference frequency forwarding, the method adopts a positioning system of the linear frequency modulation continuous wave based on the label difference frequency forwarding to position, the system comprises a main control module, M base stations and N labels to be positioned, wherein M is a natural number not less than 3, M base stations are not collinear and have known positions, N is a natural number not less than 1, and signals are transmitted between the main control module and the base stations through a television cable; the main control module is used for generating LFMCW signals and reference signals of the whole system, transmitting the LFMCW signals and the reference signals to the base station, receiving and processing forwarding signals from the base station, and resolving the position information of the label to be positioned according to the processed forwarding signals; the base station is used for receiving the LFMCW signal and the reference signal transmitted by the main control module, processing the LFMCW signal, transmitting the processed LFMCW signal to the label to be positioned, receiving and processing a forwarding signal from the label to be positioned, and transmitting the processed forwarding signal to the main control module; the base station performs frequency mixing processing when processing both LFMCW signals and forwarding signals, and the reference signal is used as a reference source when a local oscillator signal used in the frequency mixing processing is generated; the label to be positioned is used for receiving and transmitting LFMCW signals from a base station by difference frequency;

the label to be positioned comprises a differential rotation module, a communication module B and a power supply module; the difference conversion module is used for receiving the LFMCW signal from the base station, mixing the LFMCW signal and transmitting the mixed LFMCW signal to the base station, so that difference frequency is generated between the frequency of the signal received and transmitted to the base station; the differential conversion module comprises an antenna B1, a band-pass filter D1, a low-noise amplifier B, a mixer C, a band-pass filter D2, a power amplifier C and an antenna B2 which are connected in sequence, wherein the mixer C is connected with a frequency synthesizer C; the communication module B is used for communicating with the main control module, and the main control module can schedule the label to be positioned; the power supply module is used for supplying power to the differential conversion module, and also comprises a control module which is connected with the communication module B and is used for receiving and returning instructions of the main control module; the master control module comprises a clock source, a communication module A, a digital signal processing module, a frequency synthesizer A, LFMCW generation module and a synthesis/distributor which are sequentially connected, wherein the output end of the synthesis/distributor is simultaneously connected with at least M band-pass filters A, and the clock source is connected with the digital signal processing module and the frequency synthesizer A; the main control module further comprises at least M signal receiving units, each signal receiving unit comprises an A/D module A, a power amplifier A, a low-pass filter A, a frequency mixer A and a band-pass filter B which are sequentially connected, and the A/D module A is connected with the digital signal processing module; the frequency synthesizer A is also simultaneously connected with the synthesizer/distributor and the mixers A of all the signal receiving units; the output end of the band-pass filter A and the input end of the band-pass filter B are connected with a base station;

each base station has the same internal structure and comprises a band-pass filter C2, a mixer B1, a band-pass filter C3, a power divider B, a power amplifier B1 and an antenna A1 which are connected in sequence; the base station further comprises a power amplifier B3, a band-pass filter C6, a mixer B3, a band-pass filter C5, a mixer B2, a low-noise amplifier A, a band-pass filter C4 and an antenna A2 which are connected in sequence, and the power divider B is connected with the mixer B2; the base station also comprises a band-pass filter C1, wherein the band-pass filter C1 is connected with a frequency synthesizer B, and the frequency synthesizer B is connected with a mixer B1 and a mixer B3;

the positioning method comprises the following steps:

s1: the main control module sends a positioning instruction to a communication module B of the tag to be positioned through a communication module A, wherein the communication module A and the communication module B can be ZigBee communication modules, the tag to be positioned starts a power supply module after receiving the positioning instruction, the power supply module supplies power to the differential rotation module, and meanwhile the tag to be positioned returns a ready instruction to the main control module;

s2: after receiving the positioning request, the main control module triggers the frequency synthesizer a to generate a reference signal, preferably, the reference signal may be a single frequency signal, triggers the LFMCW generation module to generate an LFMCW signal with the reference signal, then combines the reference signal and the LFMCW signal into one signal, and transmits the combined signal to M base stations, preferably, the main control module transmits the combined signal to M base stations in a manner of a cable television trunk driver; LFMCW signal has a start frequency of f₀Modulation bandwidth of B and modulation period of T_mThe frequency modulation slope is k ═ B/T_mSet as f (t), the frequency of the reference signal is f_s；

S3: after receiving the synthesized signal from the main control module, the M base stations filter the synthesized signal in two paths to obtain a reference signal and an LFMCW signal respectively, wherein the reference signal is sent to a frequency synthesizer B as a frequency reference, the frequency synthesizer B generates a first local oscillation signal and a second local oscillation signal, the LFMCW signal after filtering and the first local oscillation signal in each base station are mixed in a frequency mixer B1, the frequencies of the first local oscillation signals are f respectively_L2-1、f_L2-2、…、f_L2-MObtaining the starting frequency f of the signals transmitted by the M base stations to the tag to be positioned_RF2-1＝|f₀-f_L2-1L or f_RF2-1＝f₀+f_L2-1、f_RF2-2＝|f₀-f_L2-2L or f_RF2-2＝f₀+f_L2-2、…、f_RF2-M＝|f₀-f_L2-ML or f_RF2-M＝f₀+f_L2-MThe signal frequency bands are all in the receiving frequency band of the antenna B1, and finally, the signals are transmitted to a positioning area by the base station antenna A1 after power amplification; a second local oscillation signal generated by the frequency synthesizer B is sent to a frequency mixer B3;

s4: after receiving the signals from the M base stations, the label to be positioned firstly filters and amplifies the signals, and then the local oscillator frequency generated by the label to be positioned and the frequency synthesizer C is f_L3Local oscillator ofThe signals are mixed in a mixer C to obtain the initial frequency f transmitted to M base stations by the label to be positioned_RF3-1＝f₀+f_L2-1+f_L3Or f_RF3-1＝|f₀+f_L2-1-f_L3|、f_RF3-2＝f₀+f_L2-2+f_L3Or f_RF3-2＝|f₀+f_L2-2-f_L3|、…、f_RF3-M＝f₀+f_L2-M+f_L3Or f_RF3-M＝|f₀+f_L2-M-f_L3I, all signals are in a receiving frequency band of an antenna A2, and are transmitted back to the indoor space through an antenna B2 of a tag to be positioned after power amplification;

s5: after receiving the signals forwarded by the tag to be positioned, the M base stations firstly filter and amplify, then input the signals into a mixer B2 to mix with the local LFMCW signals output by the power divider B, and after filtering by a band-pass filter C5, obtain the signals of the base station forwarded by the tag to be positioned and the positioning signals after beat deskew of the local signals, wherein the frequencies of the radio frequency positioning signals of the M base stations are respectively as follows: f. of_2-1＝f_L3+f_τ1、f_2-2＝f_L3+f_τ2、…、f_2-M＝f_L3+f_τMAmplified by a power amplifier B2, and the local oscillator frequency generated by the frequency synthesizer B is f_L2-0The second local oscillator signal enters a mixer B3 for frequency mixing to obtain intermediate frequency signals with the frequencies f_IF2-1＝|f_L3-f_L2-0|+f_τ1Or f_IF2-1＝f_L3+f_τ1+f_L2-0、f_IF2-2＝|f_L3-f_L2-0|+f_τ2Or f_IF2-2＝f_L3+f_τ2+f_L2-0、…、f_IF2-M＝|f_L3-f_L2-0|+f_τMOr f_IF2-M＝f_L3+f_τM+f_L2-0And the frequency band is an intermediate frequency signal on the television band, i.e. f_IF2-i＝|f_L3-f_L2-0|+f_τiWherein, i is 1,2, …, M, and finally, after power amplification, the signal is transmitted back to the main control module by way of the cable television main line driver; as described aboveIn the frequency of the intermediate frequency signal, the first item is a television frequency band difference frequency item configured by the system, and the local oscillation frequency in the label to be positioned is f_L3And the local oscillator frequency in the base station is f_L2-0The second term is caused by signal transmission delay and comprises a space bidirectional transmission delay formed by transmitting the base station to the label to be positioned and forwarding the label to be positioned to the base station, wherein the space bidirectional transmission delay comprises distance information required by system positioning;

s6: after receiving the intermediate frequency signals from the M base stations, the main control module generates a local oscillation frequency f with the frequency synthesizer A_L1Is mixed in a mixer A to obtain a local oscillator signal with a frequency f_1-1＝f_L1+|f_L3+f_τ1-f_L2-0L or f_1-1＝|f_L3+f_τ1-f_L2-0-f_L1|、f_1-2＝f_L1+|f_L3+f_τ2-f_L2-0L or f_1-2＝|f_L3+f_τ2-f_L2-0-f_L1|、…、f_1-M＝f_L1+|f_L3+f_τM-f_L2-0L or f_1-2＝|f_L3+f_τM-f_L2-0-f_L1I and a frequency within the passband of the low-pass filter A, i.e. f_1-i＝|f_L3+f_τi-f_L2-0-f_L1|＝|f_L3-f_L2-0-f_L1|+f_τiWherein i ═ 1,2, …, M; in the frequencies of the baseband positioning signals, a first item is a difference frequency item configured by a system, a second item is formed by signal transmission delay, and then the difference frequency item is amplified by a power amplifier A and sent to an A/D module A;

s7: the A/D module A converts the sent baseband positioning signals into digital baseband signals, then sends the digital baseband signals to the digital signal processing module, the digital signal processing module carries out fast discrete Fourier transform on each digital baseband signal to obtain the frequency spectrum of the digital baseband signals, and then the frequency spectrum peak value f of the M baseband positioning signals is judged through a threshold_1-iWherein i ═ 1,2, …, M;

s8: the frequency value f_1-iSubtracting the difference frequency term of the system configuration, and then subtracting the frequency values two by two to obtain C (2, M) frequency differences △ f_ijWhere i, j is 1,2, …, M, C (2, M) refers to the number of combinations of two out of M bss, for example, if there are 3 bss, then a total of C (2,3) is 6 frequency differences, where the frequency difference is the frequency difference caused by the two-way propagation delay from the tag to be positioned to the M bss, and the formula △ R is used to determine the frequency difference_ij＝△f_ijT_mc/2B, calculating the distance difference from the label to each receiving base station, wherein c is the speed of light; on the basis, the position of the label to be positioned is calculated by utilizing a hyperbolic curve cross positioning principle according to the position where each base station is installed; as described above, the hyperbolic positioning method using the distance difference can eliminate the influence of the random frequency error generated by the local oscillator of the tag to be positioned, i.e., the frequency lengthener C, on the positioning accuracy of the system.

S9: the main control module sends an ending instruction to a communication module B of the tag to be positioned through the communication module A, and the tag to be positioned turns off the power supply module after receiving the instruction.

Further, the distance R between the label to be positioned and the M base stations and the frequency modulation period T of the LFMCW signal_mShould satisfy T_m>2R/c, wherein c is 3 × 10⁸m/s is the speed of light; the first local oscillation signals in the M base stations in the step S3 have the frequency f in sequence_L2-1、f_L2-2、…、f_L2-M，f_L2-1、f_L2-2、…、f_L2-MNot equal, an equal frequency difference △ f, i.e., f, is generally set_L2-i＝f_L2-1+ (i-1) x △ f, wherein i ═ 1,2, …, M, △ f>0. The setting ensures that the LFMCW signal of the base station and the beat signal of the local LFMCW of the base station forwarded by the label to be positioned can be obtained when beat deskew processing is carried out in each base station.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the label to be positioned comprises a differential conversion module, wherein the differential conversion module is used for generating differential frequency between frequencies received and transmitted to a base station, and is essentially a differential frequency repeater, so that the label to be positioned does not need to be provided with a clock source and does not need to be synchronously controlled with each base station; meanwhile, LFMCW signals and reference signals generated by the main control module are both derived from a clock source in the main control module, so that the main control module and each base station only adopt one clock source and are connected with each other by adopting a television cable to form a coherent system, and therefore, synchronous control is not required to be performed between the base stations; through the arrangement, the accurate synchronous control among the main control module, the base station and the label to be positioned can be realized, the cost is low, and the implementation of the positioning scheme is good;

2. compared with the prior art, the band-pass filter C1 of the base station is connected with the frequency synthesizer B and used for filtering out a reference signal from a signal from the main control module, the reference signal is used as a reference source of a signal generated by the frequency synthesizer B, the frequency synthesizer B is used for generating a stable signal as a local oscillator signal of the mixer B1, namely the local oscillator signal is not provided by amplifying a radio frequency signal received by an antenna, so that the stable operation of each mixer can be ensured;

3. the invention adopts different initial frequencies of signals transmitted to the label to be positioned by different base stations, can ensure that when each base station beats and deskews the signal transmitted back by the label to be positioned and the original transmitted signal, the band-pass filter C5 is used for distinguishing whether the transmitted signal is transmitted to the label to be positioned by the base station, thereby avoiding the signals from other base stations transmitted by the label to be positioned from reaching the base station and forming mutual interference among the base stations;

4. the invention adopts the closed circuit television cable to realize the signal transmission between the main control module and the base station, thereby enhancing the anti-interference performance of the system signal transmission and realizing low cost, thereby improving the cost performance of the whole indoor positioning system;

5. the invention adopts a hyperbolic positioning method of distance difference, and can eliminate the influence of random frequency error of a local oscillator of a label to be positioned on the positioning precision of the system.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a schematic diagram of a positioning system according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a main control module according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a base station according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a tag to be located according to an embodiment of the present invention;

fig. 5 is a flow chart of the operation of the positioning system of one embodiment of the present invention.

Detailed Description

The invention discloses a positioning system and a method of linear frequency modulation continuous waves based on label difference frequency forwarding.A main control module is adopted to uniformly transmit LFMCW signals to each base station, each base station transmits signals to a label to be positioned, and the received signals of the label to be positioned are forwarded back to the base station for processing and resolving, thereby avoiding the synchronization problem between the base stations and between the labels of the base stations; furthermore, the main control module and each base station transmit signals mutually through cable television cables, thereby realizing closed-circuit transmission of the signals and ensuring strong anti-interference performance and low cost in the signal transmission process; the transmitting and receiving antennas of the base station and the tag adopt different frequency bands to obtain good transmitting and receiving isolation, so that the system can increase the positioning range by increasing the transmitting power of the base station and the tag.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.

Example 1:

the positioning system of the chirp continuous wave based on the tag difference frequency forwarding shown in fig. 1 and 5 includes a main control module, M base stations, and N tags to be positioned, where M is a natural number not less than 3, M base stations are not collinear and the two-dimensional plane position is known, and N is a natural number not less than 1; the main control module and the base station transmit signals through a television cable; the main control module is used for generating LFMCW signals and reference signals of the whole system, transmitting the LFMCW signals and the reference signals to the base station, receiving and processing forwarding signals from the base station, and resolving the position information of the label to be positioned according to the processed forwarding signals; the base station is used for receiving the LFMCW signal and the reference signal transmitted by the main control module, processing the LFMCW signal, transmitting the processed LFMCW signal to the label to be positioned, receiving and processing a forwarding signal from the label to be positioned, and transmitting the processed forwarding signal to the main control module; the base station performs frequency mixing processing when processing both LFMCW signals and forwarding signals, and the reference signal is used as a reference source when a local oscillator signal used in the frequency mixing processing is generated; the label to be positioned is used for receiving and transmitting LFMCW signals from the base station by difference frequency.

The structure of the label to be positioned is shown in fig. 4, and the label to be positioned comprises a differential rotation module, a communication module B and a power supply module; the difference conversion module is used for receiving the LFMCW signal from the base station, mixing the LFMCW signal and transmitting the mixed LFMCW signal to the base station, so that difference frequency is generated between the frequency of the signal received and transmitted to the base station; the communication module B is used for communicating with the main control module, and the main control module can schedule the label to be positioned; the power module is used for supplying power for the differential conversion module, and the power module further comprises a control module which is connected with the communication module B and used for receiving and returning instructions of the main control module. As shown in fig. 4, the difference conversion module includes an antenna B1, a band pass filter D1, a low noise amplifier B, a mixer C, a band pass filter D2, a power amplifier C, and an antenna B2, which are connected in sequence, and the mixer C is connected with a frequency synthesizer C. Antenna B1 and antenna B2 are used for receiving and transmitting signals from each base station, respectively, and the tag to be positioned can increase the positioning range of the system by increasing the transmission power. The band pass filter D1 and the band pass filter D2 are used for filtering signals, and the antenna B1 is connected with the band pass filter D1 and the antenna B2 is connected with the band pass filter D2, so that good isolation between transmission and reception can be obtained. The frequency synthesizer C is used for generating a local oscillator signal required by the mixer C.

As shown in fig. 2, the main control module includes a clock source, a communication module a, and a digital signal processing module, a frequency synthesizer A, LFMCW generation module, and a synthesizer/distributor connected in sequence, the output end of the synthesizer/distributor is connected with at least M band-pass filters a at the same time, the clock source is connected with the digital signal processing module and the frequency synthesizer a, and the above modules constitute a signal transmitting part of the main control module. The main control module also comprises at least M signal receiving units, and each signal receiving unit comprises an A/D module A, a power amplifier A, a low-pass filter A, a frequency mixer A and a band-pass filter B which are sequentially connected; the A/D module A is connected with the digital signal processing module; the frequency synthesizer A is connected with the synthesizer/distributor and the mixer A; and the output end of the band-pass filter A and the input end of the band-pass filter B are connected with the base station through a television cable. The frequency synthesizer A can generate a signal with stable frequency to serve as a coherent reference signal of the whole system, and the LFMCW generation module generates an LFMCW signal; the synthesis/distributor firstly synthesizes the reference signal and the LFMCW signal into a path of signal and then redistributes the signal into M paths of signals leading to M base stations; the band-pass filter A and the band-pass filter B can filter the signals to obtain signals of a required frequency band; the mixer A carries out down-conversion processing on a signal transmitted back by the base station; the power amplifier A amplifies the signal; the A/D module A samples and converts the signal into a digital signal; the digital signal processing module has the functions of digital signal processing and scheduling control for controlling the whole system; the communication module A is responsible for communication with the label to be positioned; the A/D module A and the communication module A are respectively connected with the digital signal processing module, and the communication module A is used for communicating with the label to be positioned to realize the scheduling function.

Each base station has the same internal structure, and as shown in fig. 3, the base station includes a band-pass filter C2, a mixer B1, a band-pass filter C3, a power divider B, a power amplifier B1, an antenna a1, a band-pass filter C1 and a frequency synthesizer B, which are connected in sequence, and the above modules constitute a signal transmitting part of the base station; the base station also comprises a power amplifier B3, a band-pass filter C6, a mixer B3, a power amplifier B2, a band-pass filter C5, a mixer B2, a low-noise amplifier A, a band-pass filter C4 and an antenna A2 which are connected in sequence, and the modules form a signal receiving part of the base station; the power divider B is connected with a mixer B2; the base station also comprises a band-pass filter C1, wherein the band-pass filter C1 is connected with a frequency synthesizer B, and the frequency synthesizer B is connected with a mixer B1 and a mixer B3. The antenna A1 is used for transmitting LFMCW signals of a certain frequency band, the antenna A2 is connected with the band-pass filter C4 and is used for receiving LFMCW signals which are forwarded by the difference frequency of the tag to be positioned and have another frequency band different from the transmitting frequency band, so that the system has good transmitting and receiving isolation, and preferably, the base station can increase the positioning range of the system by increasing the transmitting power. The band-pass filter C1 is connected to the frequency synthesizer B for filtering out a reference signal from the main control module, the reference signal is used as a reference source of the signal generated by the frequency synthesizer B, the frequency synthesizer B is used for generating a stable signal as a first local oscillation signal of the mixer B1, and the frequency synthesizer B further generates another second local oscillation signal as the mixer B3. The band-pass filter C2 is used to filter the LFMCW signal from the main control module, then the signal is up-converted in the mixer B1, filtered by the band-pass filter C3, and then divided into two paths by the power divider B, one path of signal is amplified by the power amplifier B1 and transmitted through the antenna a1, and the other path of signal is used as the local oscillator input signal of the mixer B2 of the receiving part of the base station. And the antenna A2 is connected with the band-pass filter C4 and is used for receiving the LFMCW signal of the other frequency band forwarded by the label to be positioned. And the mixer B2 is connected with the band-pass filter C5 and is used for deskewing the LFMCW signal forwarded by the tag to be positioned and the LFMCW signal beat originally transmitted by the base station. The mixer B3 is connected to a band pass filter C6 for down converting the beat signal for transmission back to the master control module.

In this embodiment, the reference signal is a single frequency signal, and the frequency of the reference signal is not included in the frequency range of the LFMCW signal; and the initial frequencies of the signals transmitted to the label to be positioned by different base stations are different, that is, when the LFMCW signals output by the band-pass filter C2 are up-converted, the frequency synthesizer B is used for generating local oscillation signals generated by the frequency mixer B1 which are different from different base stations, so that the LFMCW signals transmitted to the label to be positioned by each base station have a certain initial frequency difference, thus ensuring that when the signals transmitted back by the label to be positioned by each base station and the original transmission signals are deskewed, the band-pass filter C5 is used for distinguishing whether the forwarding signals are transmitted to the label to be positioned by the base station, thereby avoiding the signals from other base stations forwarded by the label to be positioned from reaching the base station and forming mutual interference between the base stations.

The method for indoor positioning by the positioning system in the embodiment comprises the following steps:

s1: the main control module sends a positioning instruction to a ZigBee communication module B of the tag to be positioned through the ZigBee communication module A, the tag to be positioned turns on the power supply module after receiving the positioning instruction, and a ready instruction is returned to the main control module;

s2: after receiving the positioning request, the main control module triggers the frequency synthesizer A to generate a reference signal, then triggers the LFMCW generation module to generate an LFMCW signal by the reference signal, then synthesizes the reference signal and the LFMCW signal into a path of signal, and transmits the synthesized signal of the LFMCW signal and the reference signal to M base stations through a closed circuit television cable; LFMCW signal has a start frequency of f₀Modulation bandwidth of B and modulation period of T_mThe frequency modulation slope is k ═ B/T_mSet as f (t), the frequency of the reference signal is f_s；

S3: after receiving the synthesized signal from the main control module, the M base stations filter the synthesized signal in two paths to obtain a reference signal and an LFMCW signal respectively, wherein the reference signal is used as a frequency reference of a frequency synthesizer B, the frequency synthesizer B generates a first local oscillation signal and a second local oscillation signal, the LFMCW signal after filtering and the first local oscillation signal are mixed in a frequency mixer B1, the frequencies of the first local oscillation signals are f respectively_L2-1、f_L2-2、…、f_L2-MObtaining the starting frequency f of the signals transmitted by the M base stations to the tag to be positioned_RF2-1＝|f₀-f_L2-1L or f_RF2-1＝f₀+f_L2-1、f_RF2-2＝|f₀-f_L2-2L or f_RF2-2＝f₀+f_L2-2、…、f_RF2-M＝|f₀-f_L2-ML or f_RF2-M＝f₀+f_L2-MThe mixed signal is amplified in power and then transmitted to a positioning area by a base station antenna A1; a second local oscillation signal generated by the frequency synthesizer B is sent to a frequency mixer B3; in this step, f_L2-1、f_L2-2、…、f_L2-MNot equal, an equal frequency difference is generally set△f，f_L2-i＝f_L2-1+ (i-1) x △ f, wherein i ═ 1,2, …, M, △ f>0；

S4: after receiving the signals from the M base stations, the label to be positioned firstly filters and amplifies the signals, and then the local oscillator frequency generated by the label to be positioned and the frequency synthesizer C is f_L3The local oscillator signal is mixed in the mixer C to obtain the initial frequency f transmitted to M base stations by the label to be positioned_RF3-1＝f₀+f_L2-1+f_L3Or f_RF3-1＝|f₀+f_L2-1-f_L3|、f_RF3-2＝f₀+f_L2-2+f_L3Or f_RF3-2＝|f₀+f_L2-2-f_L3|、…、f_RF3-M＝f₀+f_L2-M+f_L3Or f_RF3-M＝|f₀+f_L2-M-f_L3The signal of | is finally transmitted back to the indoor space by the antenna B2 of the tag to be positioned after power amplification;

s5: after receiving the signals forwarded by the tags to be positioned, the M base stations firstly carry out filtering amplification, then input the signals into a mixer B2 to carry out frequency mixing with local LFMCW signals output by a power divider B, and after filtering by a band-pass filter C5, the signals of the base stations forwarded by the tags to be positioned and the positioning signals after beat deskew of the local signals are obtained, and the frequencies of the radio frequency positioning signals of the M base stations are respectively as follows in sequence: f. of_2-1、f_2-2、…、f_2-MWherein f is_2-1＝f_L3+f_τ1、f_2-2＝f_L3+f_τ2、…、f_2-M＝f_L3+f_τMAfter being amplified by a power amplifier B2, the second local oscillator frequency generated by the frequency synthesizer B is f_L2-0The local oscillator signals enter a mixer B3 for frequency mixing, and the obtained intermediate frequency signals have the frequencies f_IF2-1、f_IF2-2、…、f_IF2-MWherein f is_IF2-1＝|f_L3-f_L2-0|+f_τ1Or f_IF2-1＝f_L3+f_τ1+f_L2-0、f_IF2-2＝|f_L3-f_L2-0|+f_τ2Or f_IF2-2＝f_L3+f_τ2+f_L2-0、…、f_IF2-M＝|f_L3-f_L2-0|+f_τMOr f_IF2-M＝f_L3+f_τM+f_L2-0I.e. f_IF2-i＝|f_L3-f_L2-0|+f_τiWherein, i is 1,2, …, M, and finally, after power amplification, the signal is transmitted back to the main control module by way of the cable television main line driver; in the frequencies of the intermediate frequency signals, the first item is a television frequency band difference frequency item configured by the system, and the local oscillation frequency in the label to be positioned is f_L3And the local oscillator frequency in the base station is f_L2-0The second term is caused by signal transmission delay and comprises a space bidirectional transmission delay formed by transmitting the base station to the label to be positioned and forwarding the label to be positioned to the base station, wherein the space bidirectional transmission delay comprises distance information required by system positioning;

s6: after receiving the intermediate frequency signals from the M base stations, the main control module generates a local oscillation frequency f with the frequency synthesizer A_L1Is mixed in a mixer A to obtain a local oscillator signal with a frequency f_1-1＝f_L1+|f_L3+f_τ1-f_L2-0L or f_1-1＝|f_L3+f_τ1-f_L2-0-f_L1|、f_1-2＝f_L1+|f_L3+f_τ2-f_L2-0L or f_1-2＝|f_L3+f_τ2-f_L2-0-f_L1|、…、f_1-M＝f_L1+|f_L3+f_τM-f_L2-0L or f_1-2＝|f_L3+f_τM-f_L2-0-f_L1I M base band locating signals with frequency within the passband of the low pass filter A, i.e. f_1-i＝|f_L3+f_τi-f_L2-0-f_L1|＝|f_L3-f_L2-0-f_L1|+f_τiWherein i ═ 1,2, …, M; the first term (i.e. | f) in the frequency of the baseband positioning signal_L3-f_L2-0-f_L1|+f_τi) The difference frequency term, the second term (i.e. f) configured for the system_τi) Is the frequency difference formed by the signal transmission delay, then the M baseband positioning signal is passed throughThe amplified signal is sent to an A/D module A after being amplified by a power amplifier A;

s8: the frequency value f_1-iSubtracting the difference frequency term configured by the system, then subtracting the frequency values pairwise to obtain C (2, M) frequency differences, and obtaining the frequency difference △ f caused by the two-way transmission delay of the label to be positioned to the M base stations_ijWhere i, j is 1,2, …, M, using equation △ R_ij＝△f_ijT_mc/2B, calculating the distance difference from the label to each receiving base station, wherein c is the speed of light; on the basis, the position of the label to be positioned is calculated by utilizing a hyperbolic curve cross positioning principle according to the position where each base station is installed;

Example 2:

in addition to embodiment 1, in this embodiment, the number of base stations to be received is further limited, and for one positioning area, in consideration of redundancy of the system and signal blocking of the tag, the number of base stations is generally 4, that is, M is 4.

Correspondingly, the main control module is provided with a band-pass filter A1-A4 which are respectively connected with a base station 1-4 through a closed circuit television cable; meanwhile, the main control module comprises 4 paths of signal receiving units, which are respectively as follows: the A/D module A1, the power amplifier A1, the low-pass filter A1, the mixer A1 and the band-pass filter B1 are connected in sequence; the A/D module A2, the power amplifier A2, the low-pass filter A2, the mixer A2 and the band-pass filter B2 are connected in sequence; the A/D module A3, the power amplifier A3, the low-pass filter A3, the mixer A3 and the band-pass filter B3 are connected in sequence; and an a/D block a4, a power amplifier a4, a low-pass filter a4, a mixer a4, and a band-pass filter B4 connected in this order. The A/D modules A1 to A/D module A4 are all connected with the digital signal processing module, and the mixers A1 to A4 are all connected with the frequency synthesizer A.

In this embodiment, a specific frequency value is taken into an indoor positioning system covering a 100 × 100-meter square plane as an example to further illustrate the positioning method of the present invention, where the positioning system includes 1 tag to be positioned, and 4 base stations, which are respectively a base station 1, a base station 2, a base station 3, and a base station 4, the four base stations are located at four corners of a square, a main control module processes the center of the square, and signal transmission delays from the main control module to the four base stations are the same, and the specific positioning method is as follows:

s1: the main control module sends a positioning instruction to a ZigBee communication module B of the to-be-positioned tag through the ZigBee communication module A, the to-be-positioned tag turns on a power supply module to supply power to the differential rotation module after receiving the instruction, and a ready instruction is returned to the main control module;

s2: after the main control module receives a ready instruction returned by a label to be positioned, the frequency synthesizer A is triggered to generate a reference signal, the LFMCW generation module is triggered to generate an LFMCW signal, and then a composite signal of the two paths of signals is transmitted to each base station through a closed circuit television cable, wherein the LFMCW is f (t), and the starting frequency of the LFMCW is f (t)₀200MHz, modulation bandwidth B100 MHz, and modulation period T_m10 ms. The frequency of the reference signal is 50 MHz;

s3: after receiving the signals from the main control module, the four base stations carry out filtering in two paths to obtain f_REFThe reference signal is used as the frequency reference of a frequency synthesizer B, and the first local oscillator signals with required different frequencies are respectively f_L2-1＝2.2GHz、f_L2-2＝2.21GHz、f_L2-3＝2.22GHz、f_L2-4The LFMCW signal is mixed with the local oscillator signal in each base station in mixer B1 to obtain the starting frequency f_RF2-1＝2.4GHz、f_RF2-2＝2.41GHzf_RF2-3＝2.42GHz、f_RF2-4The LFMCW radio frequency signal of 2.43GHz is finally transmitted to the positioning space by the base station antenna a1 after power amplification;

s4: tag reception to be locatedAfter the radio frequency signal from each base station, it is first filtered and amplified, and then is generated with the local oscillator 3 at a frequency f_L3The local oscillator signals of 3.4GHz are mixed in a mixer C to obtain initial frequencies f_RF3-1＝5.8GHz、f_RF3-2＝5.81GHz、f_RF3-3＝5.82GHz、f_RF3-4The radio frequency signal of 5.83GHz, after power amplification, is emitted back to the indoor space by the tag antenna B2;

s5: after receiving the difference signals from the tags, each base station firstly filters and amplifies the difference signals, then inputs the difference signals into a mixer B2 to mix the difference signals with the local LFMCW signals output by the power divider B, and obtains base station signals forwarded by the tags and base station intermediate frequency signals after beat deskew of the base station transmitting signals after filtering by a band-pass filter C5, wherein the frequencies of the 4 base station intermediate frequency signals are respectively as follows: f. of_2-1＝3.4GHz+f_τ1(the interference intermediate frequency after the beat result of the radio frequency signals of the 1 st base station and other three base stations forwarded by the label is 3.41GHz + f_τ1、3.42GHz+f_τ1、3.43GHz+f_τ1)、f f_2-2＝3.4GHz+f_τ2、f_2-3＝3.4GHz+f_τ3、f_2-4＝3.4GHz+f_τ4After being amplified by a power amplifier B2, the second local oscillator frequency generated by the frequency synthesizer B is f_L2-0The local oscillator signals with the frequency of 3.3GHz enter a mixer B3 for frequency mixing to obtain frequency f_IF2-1＝100MHz+f_τ1(1 st base station and label forwarded other three base station RF signal beat results after mixing frequency interference frequency 200MHz + f separately_τ1、300MHz+f_τ1、400MHz+f_τ1)、f_IF2-2＝100MHz+f_τ2、f_IF2-3＝100MHz+f_τ3、f_IF2-4＝100MHz+f_τ4The intermediate frequency signal is finally filtered by a band-pass filter C6 with the center frequency of 100MHz and the bandwidth of 5MHz to remove the interference of other base stations, and then the intermediate frequency signal is amplified by power and then is transmitted back to the main control module through a television cable;

s6: after the main control module receives the transmission intermediate frequency signals from each base station, the local oscillation frequency generated by the frequency synthesizer A is f_L1The signals of 99MHz local oscillator are mixed in mixer A1Mixing in a frequency device A4 to obtain a frequency f_1-1＝1MHz+f_τ1、f_1-2＝1MHz+f_τ2、f_1-3＝1MHz+f_τ3、f_1-4＝1MHz+f_τ4The latter term is the transmission delay of the signal, and in a 100m x 100m square plane, the spatial two-way transmission delay is less than 10^-6ms, the frequency modulation slope of the system LFMCW is k ═ B/T_m＝10¹⁰The passband cut-off frequency of the low pass filter is set to be 2MHz corresponding to the latter maximum value not exceeding 10 kHz), and then the signals are respectively sent to the A/D module A1 to the A/D module A4 after being amplified in the power amplifier A1 to the power amplifier A4 and are respectively sent to the A/D module A1 to the A/D module A4 according to f_sConversion to digital positioning signal at a 4MHz sampling rate with a signal length f_sT_m4000 points;

s7: the A/D module A1 to the A/D module A4 send the digital positioning signals to the digital signal processing module, the digital signal processing module performs fast discrete Fourier transform (FFT) after compensating 0 to 4096 points for each digital baseband signal to obtain the frequency spectrum of the digital baseband signal, and then the frequency spectrum peak value f of the 4-baseband positioning signals is judged through a threshold_1-iWherein i is 1,2,3, 4;

s8: the frequency value f_1-iTwo by two subtraction result △ f frequency difference caused by two-way transmission delay from 6 labels to different base stations_ijWhere i, j is 1,2,3,4 and i ≠ j, using formula △ R_ij＝△f_ijT_mc/2B, calculating the distance difference from the label to each receiving base station, wherein c is the speed of light; on the basis, the position of the label to be positioned can be calculated by utilizing a hyperbolic curve cross positioning principle according to the position where each base station is installed;

s9: the main control module sends an ending instruction to a communication module B of the tag to be positioned through the communication module A, and the tag to be positioned closes a power supply module which supplies power to the differential rotation module after receiving the instruction.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. Linear frequency modulation continuous wave's positioning system based on label difference frequency is forwardded, including host system, M basic station, N label of awaiting positioning, wherein, M is the natural number that is not less than 3, and M basic station is not collineation and position known, and N is the natural number that is not less than 1, its characterized in that:

the main control module is used for generating LFMCW signals and reference signals of the whole system, synthesizing the reference signals and the LFMCW signals into a path of signals and transmitting the synthesized signals to M base stations; receiving and processing a positioning signal from a base station, and resolving the position information of a label to be positioned according to the processed positioning signal;

the base station is used for receiving the synthesized signal transmitted by the main control module, filtering the synthesized signal in two paths to obtain an LFMCW signal and a reference signal, processing the LFMCW signal, and transmitting the processed LFMCW signal to a label to be positioned; receiving and processing a forwarding signal from a tag to be positioned to obtain a base station signal forwarded by the tag to be positioned and a positioning signal subjected to beat and deskew on a local signal, and transmitting the positioning signal to a main control module; the base station performs frequency mixing processing when processing both LFMCW signals and forwarding signals, and the reference signal is used as a reference source when a local oscillator signal used in the frequency mixing processing is generated;

the label to be positioned is used for receiving and transmitting LFMCW signals from a base station by difference frequency;

wherein, the processing of the positioning signal from the base station by the main control module comprises:

(1) mixing the positioning signal with a local oscillator signal generated by a frequency synthesizer of a main control module to obtain a baseband positioning signal;

(2) converting the baseband positioning signal into a digital baseband signal, obtaining the frequency spectrum of the digital baseband signal through fast discrete Fourier transform, and judging the frequency spectrum peak value of the M baseband positioning signal through a threshold;

(3) subtracting the difference frequency term of the system configuration from the peak of the frequency spectrumObtaining frequency values, and subtracting the obtained frequency values to obtain C (2, M) frequency differences delta f_ijCalculating the distance difference Delta R from the tag to the base station_ij＝Δf_ijT_mc/2B, wherein c is the speed of light, T_mThe modulation period of the LFMCW signal, B is the modulation bandwidth of the LFMCW signal, and i, j is 1,2, …, M.

2. The tag difference frequency forwarding based chirp continuous wave positioning system according to claim 1, wherein the tag to be positioned comprises a difference frequency module, a communication module B and a power supply module;

the difference conversion module is used for receiving the LFMCW signal from the base station, mixing the LFMCW signal and transmitting the mixed LFMCW signal to the base station, so that difference frequency is generated between the frequency of the signal received and transmitted to the base station;

the communication module B is used for communicating with the main control module, and the main control module can schedule the label to be positioned;

the power module is used for supplying power for the differential conversion module, and the power module further comprises a control module which is connected with the communication module B and used for receiving and returning instructions of the main control module.

3. The tag difference frequency retransmission based chirp continuous wave positioning system according to claim 2, wherein the difference frequency module comprises an antenna B1, a band pass filter D1, a low noise amplifier B, a mixer C, a band pass filter D2, a power amplifier C and an antenna B2 connected in sequence, and the mixer C is connected with a frequency synthesizer C.

4. The system according to claim 3, wherein the main control module comprises a clock source, a communication module A, and a digital signal processing module, a frequency synthesizer A, LFMCW generation module, and a synthesizer/distributor connected in sequence, wherein the output end of the synthesizer/distributor is connected with at least M band-pass filters A at the same time, and the clock source is connected with the digital signal processing module and the frequency synthesizer A; the main control module further comprises at least M signal receiving units, each signal receiving unit comprises an A/D module A, a power amplifier A, a low-pass filter A, a frequency mixer A and a band-pass filter B which are sequentially connected, and the A/D module A is connected with the digital signal processing module; the frequency synthesizer A is also simultaneously connected with the synthesizer/distributor and the mixers A of all the signal receiving units; and the output end of the band-pass filter A and the input end of the band-pass filter B are connected with the base station.

5. The tag difference frequency forwarding-based chirp continuous wave positioning system according to claim 4, wherein each base station has the same internal structure, and the base station comprises a band-pass filter C2, a mixer B1, a band-pass filter C3, a power divider B, a power amplifier B1 and an antenna A1 which are connected in sequence; the base station further comprises a power amplifier B3, a band-pass filter C6, a mixer B3, a band-pass filter C5, a mixer B2, a low-noise amplifier A, a band-pass filter C4 and an antenna A2 which are connected in sequence, and the power divider B is connected with the mixer B2; the base station also comprises a band-pass filter C1, wherein the band-pass filter C1 is connected with a frequency synthesizer B, and the frequency synthesizer B is connected with a mixer B1 and a mixer B3.

6. The tag difference frequency repeating chirp-based positioning system according to any one of claims 1 to 5, wherein the reference signal is a single frequency signal and the frequency of the reference signal is not included in the frequency range of the LFMCW signal.

7. The tag difference frequency retransmission based chirp continuous wave positioning system according to claim 6, wherein the starting frequencies of signals transmitted by different base stations to a tag to be positioned are different.

8. The tag difference frequency retransmission based chirp continuous wave positioning system according to claim 7, wherein signals are transmitted between the master control module and the base station via a television cable.

9. The positioning method of the linear frequency modulation continuous wave based on the label difference frequency forwarding is characterized in that a positioning system of the linear frequency modulation continuous wave based on the label difference frequency forwarding is adopted for positioning, the system comprises a main control module, M base stations and N labels to be positioned, wherein M is a natural number not less than 3, M base stations are not collinear and have known positions, N is a natural number not less than 1, and signals are transmitted between the main control module and the base stations through television cables; the main control module is used for generating LFMCW signals and reference signals of the whole system, transmitting the LFMCW signals and the reference signals to the base station, receiving and processing forwarding signals from the base station, and resolving the position information of the label to be positioned according to the processed forwarding signals; the base station is used for receiving the LFMCW signal and the reference signal transmitted by the main control module, processing the LFMCW signal, transmitting the processed LFMCW signal to the label to be positioned, receiving and processing a forwarding signal from the label to be positioned, and transmitting the processed forwarding signal to the main control module; the base station performs frequency mixing processing when processing both LFMCW signals and forwarding signals, and the reference signal is used as a reference source when a local oscillator signal used in the frequency mixing processing is generated; the label to be positioned is used for receiving and transmitting LFMCW signals from a base station by difference frequency;

the label to be positioned comprises a differential rotation module, a communication module B and a power supply module; the difference conversion module is used for receiving the LFMCW signal from the base station, mixing the LFMCW signal and transmitting the mixed LFMCW signal to the base station, so that difference frequency is generated between the frequency of the signal received and transmitted to the base station; the differential conversion module comprises an antenna B1, a band-pass filter D1, a low-noise amplifier B, a mixer C, a band-pass filter D2, a power amplifier C and an antenna B2 which are connected in sequence, wherein the mixer C is connected with a frequency synthesizer C; the communication module B is used for communicating with the main control module, and the main control module can schedule the label to be positioned; the power supply module is used for supplying power to the differential conversion module, and also comprises a control module which is connected with the communication module B and is used for receiving and returning instructions of the main control module;

the master control module comprises a clock source, a communication module A, a digital signal processing module, a frequency synthesizer A, LFMCW generation module and a synthesis/distributor which are sequentially connected, wherein the output end of the synthesis/distributor is simultaneously connected with at least M band-pass filters A, and the clock source is connected with the digital signal processing module and the frequency synthesizer A; the main control module further comprises at least M signal receiving units, each signal receiving unit comprises an A/D module A, a power amplifier A, a low-pass filter A, a frequency mixer A and a band-pass filter B which are sequentially connected, and the A/D module A is connected with the digital signal processing module; the frequency synthesizer A is also simultaneously connected with the synthesizer/distributor and the mixers A of all the signal receiving units; the output end of the band-pass filter A and the input end of the band-pass filter B are connected with a base station;

the positioning method comprises the following steps:

s1: the main control module sends a positioning instruction to a communication module B of the tag to be positioned through a communication module A, the tag to be positioned turns on a power supply module after receiving the positioning instruction, and a ready instruction is returned to the main control module;

s2: after receiving the ready instruction, the main control module triggers the frequency synthesizer A to generate a reference signal, then triggers the LFMCW generation module to generate an LFMCW signal by the reference signal, then synthesizes the reference signal and the LFMCW signal into one path of signal, and transmits the synthesized signal to M base stations; LFMCW signal has a start frequency of f₀Modulation bandwidth of B and modulation period of T_mThe frequency modulation slope is k ═ B/T_mSet as f (t), the frequency of the reference signal is f_s；

S3: after receiving the synthesized signal from the main control module, the M base stations filter the synthesized signal in two paths to respectively obtain a reference signal and an LFMCW signal, wherein the reference signal is sent to a frequency synthesizer B as a frequency reference, the frequency synthesizer B generates a first local oscillation signal and a second local oscillation signal, the LFMCW signal after filtering and the first local oscillation signal are mixed in a frequency mixer B1, and the signal after frequency mixing is transmitted to a positioning area through a base station antenna A1 after power amplification; a second local oscillation signal generated by the frequency synthesizer B is sent to a frequency mixer B3;

s4: after receiving the signals from the M base stations, the label to be positioned firstly filters and amplifies the signals, then the amplified signals and a local oscillator signal generated by a frequency synthesizer C are subjected to frequency mixing in a frequency mixer C, and the signals subjected to frequency mixing are transmitted back to an indoor space by an antenna B2 of the label to be positioned after power amplification;

s5: after receiving the signal forwarded by the tag to be positioned, the M base stations firstly carry out filtering amplification, then input the signal into a mixer B2 to carry out frequency mixing with a local LFMCW signal output by a power distributor B, and after filtering by a band-pass filter C5, the signal of the base station forwarded by the tag to be positioned and a positioning signal after beat deskew of the local signal are obtained, after the locating signal after beat deskew is amplified by a power amplifier B2, the signal and a second local oscillation signal generated by a frequency synthesizer B enter a mixer B3 to carry out frequency mixing to obtain an intermediate frequency signal, and finally the intermediate frequency signal is transmitted back to a main control module in a mode of a cable television trunk driver after being subjected to power amplification;

s6: after receiving the intermediate frequency signals from the M base stations, the main control module generates a local oscillation frequency f with the frequency synthesizer A_L1The local oscillator signals are mixed in a mixer A to obtain baseband positioning signals, and the baseband positioning signals are amplified by a power amplifier A and then sent to an A/D module A;

s8: the frequency value f_1-iSubtracting the difference frequency term configured by the system, and then subtracting the frequency values two by two to obtain C (2, M) frequency differences delta f_ijWherein i, j ═ 1,2, …, M; the frequency difference is a pair of M base stations to which the label to be positioned is attachedThe frequency difference caused by the propagation delay is calculated by the formula Δ R_ij＝Δf_ijT_mc/2B, calculating the distance difference from the label to each receiving base station, wherein c is the speed of light; on the basis, the position of the label to be positioned is calculated by utilizing a hyperbolic curve cross positioning principle according to the position where each base station is installed;

10. The method as claimed in claim 9, wherein the distance R between the tag to be located and M base stations and the frequency modulation period T of the LFMCW signal are determined according to the tag difference frequency forwarding_mShould satisfy T_m>2R/c, wherein c is 3 × 10⁸m/s is the speed of light; in step S3, the first local oscillation signals in the M base stations have frequency f_L2-1、f_L2-2、…、f_L2-MAnd f is_L2-i＝f_L2-1+ (i-1) × Δ f, where i ═ 1,2, …, M, Δ f>0。