CN109547059B - Chirp-GFSK combined spread spectrum modulation and demodulation system - Google Patents
Chirp-GFSK combined spread spectrum modulation and demodulation system Download PDFInfo
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Abstract
The invention discloses a Chirp-GFSK combined spread spectrum modulation and demodulation system, and relates to the technical field of wireless communication. The system comprises a radio frequency part, a baseband modulator and a baseband demodulator; the baseband modulator comprises a data modulator, a frame synchronization head generator and a data frame composition module; the data modulator comprises a whitening module, a spread spectrum module and a GFSK modulation module. At a transmitting end, a system dynamically generates and transmits a Chirp waveform as a frame synchronization signal according to a GFSK spread spectrum mode, and then the data is modulated and transmitted by the GFSK; at a receiving end, symbol and frequency deviation of the signal in the channel transmission process are estimated by adopting a multi-threshold synchronization algorithm according to the frame synchronization signal Chirp, after the frequency deviation of the spread spectrum GFSK is compensated, GFSK demodulation and signal de-spreading are carried out on the spread spectrum GFSK signal, and the sending signal is recovered. The invention integrates the advantages of the Chirp modulation signal and the spread spectrum GFSK modulation signal, reduces the complexity of signal synchronization, reduces the synchronization time of weak signals, overcomes the frequency deviation of channel symbols, and reduces the complexity of signal demodulation while realizing low power consumption.
Description
Technical Field
The invention relates to the technical field of wireless communication, in particular to a Chirp-GFSK combined spread spectrum modulation and demodulation system.
Background
Currently, wireless communication is rapidly developed around the world, and has become a popular technology of common attention in global communication and the IT world, and particularly, with the comprehensive development of the world internet of things, not only is the basic technology of wireless communication continuously improved, developed and changed, but also various different types of wireless communication systems and new wireless communication technologies are continuously promoted to emerge, and the market demand for the wireless communication technology is rapidly increased. The wireless communication chip is required by the new-age Internet of things industry due to long-distance transmission, low complexity and low power consumption. The physical layer design of the Bluetooth BLE technology uses GFSK signal modulation, the design complexity is successfully reduced, the low power consumption of a communication chip is realized, and the transmission range is limited to a few meters to dozens of meters. Direct sequence spread spectrum techniques are known and can achieve very high coding gain levels, for example, a direct spread spectrum method is used in a GPS system, which achieves very good noise immunity and long-distance signal transmission. However, the GPS receiver is quite complex in design and has a very long synchronization time for weak signals. The communication system using the digital synthesis chirp symbol for modulation in the LoRa transceiver also achieves a high coding gain level, and shows excellent long-distance anti-interference performance, but the complex fourier transform algorithm adopted in the LoRa transceiver for signal receiving and demodulation greatly increases the complexity of the receiving system.
Therefore, those skilled in the art are dedicated to develop a Chirp-GFSK combined spread spectrum modem system to reduce the complexity of signal synchronization, reduce the time for synchronizing weak signals, reduce the complexity of signal demodulation while realizing low power consumption, and make it suitable for the requirement of long-distance transmission in the internet of things.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the technical problem to be solved by the present invention includes two aspects: firstly, how to reduce the complexity of signal synchronization so as to reduce the time for synchronizing weak signals; and how to reduce the signal demodulation complexity while realizing low power consumption so as to meet the requirement of long-distance transmission in the Internet of things.
In order to achieve the purpose, the invention provides a Chirp-GFSK combined spread spectrum modulation and demodulation system, which comprises a radio frequency part, a baseband modulator and a baseband demodulator; the radio frequency part comprises a first filter, a DAC module, a power amplifier, a low noise amplifier, a second filter and an ADC module; the baseband modulator comprises a data modulator, a frame synchronization head generator and a data frame composition module; the data modulator comprises a whitening module, a spread spectrum module and a GFSK modulation module; the frame synchronization head generator comprises a spread spectrum parameter configuration module and a Chirp generation module; the baseband demodulator comprises a digital filter, a frame synchronization module, a frequency offset elimination module, a GFSK demodulation module, a de-spreading module and a de-whitening module;
the frame synchronization head generator determines the Chirp signal generation length according to the spread spectrum mode configured in the spread spectrum parameter configuration module, and generates the Chirp signal through the Chirp generation module; the original sending signal is input into the data modulator and subjected to whitening processing through the whitening module, the whitened data is sent into the spread spectrum module to be subjected to direct sequence spread spectrum processing, and the spread spectrum processed data is modulated through the GFSK modulation module to obtain GFSK modulation data; the data frame composition module combines the generated Chirp signal and the GFSK modulation data into a complete data packet; the data packet sends in-phase signal component I and quadrature signal component Q data of a baseband signal to the radio frequency part through the first filter and the DAC module, the radio frequency circuit performs filtering and up-mixing, and then the power amplifier sends out a modulated radio frequency signal;
the modulated radio frequency signal is processed by the second filter and the ADC module to generate a digital signal, the digital signal is input to the digital filter of the baseband demodulator for digital filtering, the digitally filtered signal is sent to the frame synchronization module for signal synchronization, the initial position and the frequency deviation of the GFSK modulation data are determined, the frequency deviation is eliminated by the frequency deviation elimination module, the GFSK demodulation is carried out by the GFSK demodulation module, the direct sequence spread spectrum is carried out by the de-spreading module, and the de-spread data is input to the de-whitening module for de-whitening processing and then the transmission signal is recovered.
Further, the Chirp signal includes a Down-Chirp (linearly decreasing frequency) signal and an Up-Chirp (linearly increasing frequency) signal.
Further, the signal length parameters of the Down-Chirp signal and the Up-Chirp signal are changed according to configuration, the GFSK spreading parameters are determined according to the spreading parameter configuration module, and the required Down-Chirp and Up-Chirp signal length parameters are determined according to the GFSK spreading parameters.
Further, the Chirp signal generation module generates the Up-Chirp signal to perform symbol synchronization on the received signal, and generates the Down-Chirp signal to perform frequency deviation estimation on the received signal.
Further, the original transmission signal includes a Device address (Device Addr), Header information (Header), packet data (Payload), and a check segment (CRC).
Further, the direct sequence spread spectrum processing is specifically operated to perform exclusive or processing on an output value of a pseudo-random generator in the spread spectrum module and the whitened data.
Further, the specific method for the frame synchronization module to perform signal synchronization is to estimate the symbol and frequency deviation Δ f of the signal in the channel transmission process by using a multi-threshold synchronization algorithm, so as to achieve symbol synchronization and frequency deviation estimation.
Further, the frequency offset estimate is calculated as,
the frequency deviation Δ f is (Posi2-Posi1-Lchirp)/2 BW/Lchirp,
wherein, Posi2 is the end position of the Up-Chirp signal, Posi1 is the end position of the Down-Chirp signal, Lchirp is the length parameter of the Chirp signal, and BW is the bandwidth of the original transmission signal.
Further, the frequency offset cancellation module includes a mixer, and cancels the frequency offset by using the mixer.
Further, the direct sequence spread spectrum is specifically operated by determining the size of the transmitted data after the locally generated pseudo-random sequence is xor-accumulated with the received sequence.
Compared with the prior art, the invention has the beneficial technical effects that:
the invention integrates the advantages of a Chirp modulation signal and a spread spectrum GFSK modulation signal, and designs a spread spectrum modulation and demodulation wireless communication system combining the Chirp and the GFSK. The Chirp signal is used as a frame synchronization signal, so that the complexity of signal synchronization is reduced, the time for synchronizing weak signals is shortened, and the frequency deviation of channel symbols is overcome. By using the GFSK spread spectrum technology, the signal demodulation complexity is reduced while low power consumption is realized, and the method is suitable for the requirement of long-distance transmission in the Internet of things.
The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.
Drawings
FIG. 1 is a schematic diagram of a system configuration according to a preferred embodiment of the present invention;
FIG. 2 is a graph showing the instantaneous frequencies of the Up-Chirp signal and the Down-Chirp signal in accordance with a preferred embodiment of the present invention;
FIG. 3 is a schematic diagram of the operation of the spreading module in a preferred embodiment of the present invention;
FIG. 4 is a diagram of a complete packet frame structure in a preferred embodiment of the present invention;
fig. 5 is a flow chart of Chirp signal synchronization in a preferred embodiment of the present invention;
fig. 6 is a schematic diagram of the operation of the despreading module in a preferred embodiment of the invention.
The system comprises a radio frequency part 1, a radio frequency part 2, a baseband modulator 3, a baseband demodulator 101, a first filter 102, a DAC module 103, a power amplifier 104, a low noise amplifier 105, a second filter 106, an ADC module 2, a baseband modulator 21, a data modulator 22, a frame synchronization header generator 23, a data frame forming module 211, a whitening module 212, a spreading module 213, a GFSK modulation module 221, a spreading parameter configuration module 222, a Chirp generation module 301, a digital filter 302, a frame synchronization module 303, a frequency offset eliminating module 304, a GFSK demodulation module 305, a despreading module 306 and a whitening module 306.
Detailed Description
The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.
As shown in fig. 1, the present invention provides a Chirp-GFSK joint spread spectrum modulation and demodulation system, which includes a radio frequency part 1, a baseband modulator 2 and a baseband demodulator 3. The radio frequency part 1 comprises a first filter 101, a DAC module 102, a power amplifier 103, a low noise amplifier 104, a second filter 105 and an ADC module 106. The baseband modulator 2 includes a data modulator 21, a frame synchronization header generator 22, and a data frame composition module 23. The data modulator 21 includes a whitening module 211, a spreading module 212, and a GFSK modulation module 213. The frame sync header generator 22 includes a spreading parameter configuration module 221 and a Chirp generation module 222. The baseband demodulator 3 includes a digital filter 301, a frame synchronization module 302, a frequency offset cancellation module 303, a GFSK demodulation module 304, a despreading module 305, and a de-whitening module 306.
At the transmitting end, the frame synchronization header generator 22 determines the length of Chirp signal generation according to the spreading mode configured in the spreading parameter configuration module 221, and generates a Chirp signal through the Chirp generation module 222. The Chirp signal comprises a Down-Chirp signal and an Up-Chirp signal, and the two signals are used for receiving end symbol synchronization and frequency offset estimation. The instantaneous frequencies of the Down-Chirp and Up-Chirp signals are shown in fig. 2. When the system works, the Chirp signal generation module 222 generates an Up-Chirp signal to perform symbol synchronization on a received signal, and then generates a Down-Chirp signal to perform frequency deviation estimation on the received signal. The signal length parameters of the Down-Chirp (frequency linear decreasing) signal and the Up-Chirp (frequency linear increasing) signal are changed according to configuration, the GFSK spreading parameters are determined according to the spreading parameter configuration module 221, and then the required Down-Chirp and Up-Chirp signal length parameters are determined according to the GFSK spreading parameters.
At the transmitting end, the original transmission signal includes a Device address (Device Addr), Header information (Header), packet data (Payload), and a check segment (CRC). The original transmission signal is input to the data modulator 21, and is whitened by the whitening module 211, the whitened data is sent to the spreading module 212 for direct sequence spreading, and the spread data is modulated by the GFSK modulation module 213 to obtain GFSK modulated data. As shown in fig. 3, the direct sequence spread spectrum processing is specifically operated by xoring the output value of the pseudo-random generator in the spreading module 212 with the whitened data.
The data frame composing module 23 combines the generated Chirp signal and GFSK modulated data into a complete data packet, and the frame structure of the complete data packet is as shown in fig. 4. The data packet sends the in-phase signal component I and the quadrature signal component Q data of the baseband signal to the radio frequency part 1 through the first filter 101 and the DAC module 102, and the radio frequency circuit performs filtering up-mixing, and then the power amplifier 103 sends out the modulated radio frequency signal.
At the receiving end, the modulated rf signal is processed by the second filter 105 and the ADC module 106 to generate a digital signal, which is input to the digital filter 301 of the baseband demodulator 3 for digital filtering. The digitally filtered signal is sent to a frame synchronization module 302 for signal synchronization, the start position and the frequency deviation of the GFSK modulated data are determined, then the signal is input to a frequency deviation elimination module 303, the frequency deviation elimination module 303 comprises a mixer, the frequency deviation is eliminated by using the mixer, after the frequency deviation is eliminated, GFSK demodulation is performed by a GFSK demodulation module 304, direct sequence and sequence spread spectrum are performed by a de-spreading module 305, and finally the de-spread data is input to a de-whitening module 306 for de-whitening processing and then the original transmission signal is recovered.
In the processing process of the receiving end, the specific method for the frame synchronization module 302 to perform signal synchronization is to estimate the symbol and frequency deviation Δ f of the signal in the channel transmission process by using the multi-threshold synchronization algorithm, so as to achieve symbol synchronization and frequency deviation estimation, and the specific operation flow is shown in fig. 5.
As shown in fig. 5, first, the frame synchronization module 302 determines the length L of Chirp signal generation according to the currently configured spreading modechirpGenerating an Up-Chirp signal according to the Chirp length parameter, and correlating the generated Up-Chirp signal with the received data to accumulate energy P1corrMeanwhile, the signal energy P1 of the received data is calculatedsigAccording to the received signal energy P1sigIs selected to correspond to the energy threshold P1thWhen the accumulated energy P1 is correlatedcorrGreater than a threshold value P1thThen, the correlation energy at this time is defined as P1corr_1Continuously searching correlation accumulation energy P1 of N pointscorr_2To P1corr_NComparison and judgment set [ P1 ]corr_1，P1corr_2，……，P1corr_N]The maximum value is the end position Posi1 of the Down-Chirp signal, at this moment, the Down-Chirp signal with the same length is generated, and the Down-Chirp signal starts to be transmittedAnd searching the position of the Up-Chirp signal. Similarly, the generated Up-Chirp signal and the received data are correlated and accumulated with energy P2corrMeanwhile, the signal energy P2 of the received data is calculatedsigAccording to the received signal energy P2sigIs selected to correspond to the energy threshold P2thWhen the accumulated energy P2 is correlatedcorrGreater than a threshold value P2thThen, the correlation energy at this time is defined as P2corr_1Continuously searching correlation accumulation energy P2 of N pointscorr_2To P2corr_NComparison and judgment set [ P2 ]corr_1，P2corr_2，……，P2corr_N]And the position of the maximum value is the transmission signal Up-Chirp end position Posi 2. According to the previously obtained Down-Chirp position Posi1, Up-Chirp position Posi2 and Chirp signal length parameter LchirpThe frequency deviation Δ f can be calculated as
Δf＝(Posi2-Posi1-Lchirp)/2*BW/Lchirp
Where BW is the bandwidth of the transmitted signal.
As shown in fig. 6, the despreading module 305 performs direct sequence spread spectrum by determining the size of the transmitted data by performing xor accumulation of the locally generated pseudo-random sequence and the received sequence.
The invention integrates the advantages of Chirp modulation signals and spread spectrum GFSK modulation signals, greatly reduces the signal synchronization calculation complexity of spread spectrum GFSK through a Chirp modulation mode, reduces the weak signal synchronization time, reduces the signal demodulation complexity while realizing low power consumption by adopting the GFSK spread spectrum technology, simplifies the hardware cost for realizing a spread spectrum system chip, and can meet the modulation and demodulation performance requirements of a communication system.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (8)
1. A Chirp-GFSK combined spread spectrum modulation and demodulation system is characterized by comprising a radio frequency part, a baseband modulator and a baseband demodulator; the radio frequency part comprises a first filter, a DAC module, a power amplifier, a low noise amplifier, a second filter and an ADC module; the baseband modulator comprises a data modulator, a frame synchronization head generator and a data frame composition module; the data modulator comprises a whitening module, a spread spectrum module and a GFSK modulation module; the frame synchronization head generator comprises a spread spectrum parameter configuration module and a Chirp generation module; the baseband demodulator comprises a digital filter, a frame synchronization module, a frequency offset elimination module, a GFSK demodulation module, a de-spreading module and a de-whitening module;
the frame synchronization head generator determines the Chirp signal generation length according to the spread spectrum mode configured in the spread spectrum parameter configuration module, and generates the Chirp signal through the Chirp generation module; the original sending signal is input into the data modulator and subjected to whitening processing through the whitening module, the whitened data is sent into the spread spectrum module to be subjected to direct sequence spread spectrum processing, and the spread spectrum processed data is modulated through the GFSK modulation module to obtain GFSK modulation data; the data frame composition module combines the generated Chirp signal and the GFSK modulation data into a complete data packet; the data packet sends in-phase signal component I and quadrature signal component Q data of a baseband signal to the radio frequency part through the first filter and the DAC module, the radio frequency circuit performs filtering and up-mixing, and then the power amplifier sends out a modulated radio frequency signal;
the modulated radio frequency signal is processed by the second filter and the ADC module to generate a digital signal, the digital signal is input to the digital filter of the baseband demodulator for digital filtering, the digitally filtered signal is sent to the frame synchronization module for signal synchronization, the initial position and the frequency deviation of the GFSK modulation data are determined, the frequency deviation is eliminated by the frequency deviation elimination module, the GFSK demodulation is carried out by the GFSK demodulation module, the direct sequence spread spectrum is carried out by the de-spreading module, and the de-spread data is input to the de-whitening module for de-whitening processing and then the transmission signal is recovered;
the Chirp signal comprises a Down-Chirp signal and an Up-Chirp signal, wherein the Down-Chirp signal is a frequency linear decreasing signal, and the Up-Chirp signal is a frequency linear increasing signal;
and the signal length parameters of the Down-Chirp signal and the Up-Chirp signal are changed according to configuration, the GFSK spreading parameters are determined according to the spreading parameter configuration module, and the required signal length parameters of the Down-Chirp signal and the Up-Chirp signal are determined according to the GFSK spreading parameters.
2. The Chirp-GFSK combined spread spectrum modem system as claimed in claim 1, wherein the Chirp generation module generates the Up-Chirp signal to perform symbol synchronization on the received signal, and generates the Down-Chirp signal to perform frequency offset estimation on the received signal.
3. The Chirp-GFSK joint spread spectrum modem system according to claim 1, wherein the original transmission signal comprises a Device address (Device Addr), Header information (Header), packet data (Payload), and a check segment (CRC).
4. The Chirp-GFSK joint spread spectrum modem system according to claim 1, wherein the direct sequence spread spectrum processing is specifically operative to xor the output of the pseudo-random generator in the spreading module with the whitened data.
5. The Chirp-GFSK combined spread spectrum modem system as claimed in claim 1, wherein the frame synchronization module performs signal synchronization by estimating symbol and frequency deviation Δ f of the signal during channel transmission using a multi-threshold synchronization algorithm to achieve symbol synchronization and frequency deviation estimation.
6. The Chirp-GFSK joint spread spectrum modem system of claim 5, wherein the frequency deviation estimate is calculated as,
the frequency deviation Δ f is (Posi2-Posi1-Lchirp)/2 BW/Lchirp,
wherein, Posi2 is the end position of the Up-Chirp signal, Posi1 is the end position of the Down-Chirp signal, Lchirp is the length parameter of the Chirp signal, and BW is the bandwidth of the original transmission signal.
7. The Chirp-GFSK joint spread spectrum modem system of claim 1, wherein the frequency offset cancellation module comprises a mixer, and wherein the mixer is utilized to cancel frequency offset.
8. The Chirp-GFSK combined spread spectrum modem system as claimed in claim 1, wherein the direct sequence column spreading is specifically operated to determine the size of the transmitted data by XOR-accumulating the locally generated pseudo-random sequence with the received sequence.
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| CN110071732B (en) * | 2019-04-16 | 2021-01-08 | 苏州磐启微电子有限公司 | Low-power-consumption wireless receiving method and receiving system thereof |
| CN110572337B (en) * | 2019-09-12 | 2021-11-05 | 重庆邮电大学 | Channel estimation and equalization method for Chirp modulation signal |
| CN110581750B (en) * | 2019-11-11 | 2020-03-27 | 上海磐启微电子有限公司 | Modulator, demodulator and wireless communication system |
| CN111181596B (en) * | 2019-12-31 | 2021-11-30 | 北京升哲科技有限公司 | Modulation-demodulation method and system |
| CN111181600B (en) * | 2019-12-31 | 2022-01-11 | 北京升哲科技有限公司 | Chirp spread spectrum modulation and demodulation method and system based on QPSK |
| CN111245475B (en) * | 2020-01-10 | 2021-10-15 | 上海感悟通信科技有限公司 | Wireless communication data transmitting method, receiving method, wireless communication method and device |
| CN112134820B (en) * | 2020-08-24 | 2022-01-14 | 北京智芯微电子科技有限公司 | Modulation method, modulator, demodulation method, demodulator, communication method and system |
| CN112904386A (en) * | 2021-01-15 | 2021-06-04 | 武汉梦芯科技有限公司 | Method and system for compensating LoRa Doppler frequency offset based on GNSS |
| CN114665918B (en) * | 2022-03-25 | 2023-10-27 | 深圳市力合微电子股份有限公司 | Multi-slope Chirp signal generation and despreading method with error correction capability |
| CN115174323B (en) * | 2022-06-29 | 2023-11-28 | 北京智芯微电子科技有限公司 | Frequency modulation signal detection method, frequency modulation signal detection device, electronic equipment and storage medium |
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