CN112114306B - Method and device for improving measuring precision of detector - Google Patents
Method and device for improving measuring precision of detector Download PDFInfo
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- CN112114306B CN112114306B CN201910534530.7A CN201910534530A CN112114306B CN 112114306 B CN112114306 B CN 112114306B CN 201910534530 A CN201910534530 A CN 201910534530A CN 112114306 B CN112114306 B CN 112114306B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
- G01S7/415—Identification of targets based on measurements of movement associated with the target
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Abstract
A method and apparatus for improving the measurement accuracy of a detector, the method comprising: s1, converting Doppler signals into analysis signals, and dividing the analysis signals into a first analysis signal and a second analysis signal; s2, demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value; s3, realizing reproduction of the detection signal and generating a reproduction signal; s4, compensating the second analysis signal so as to enable the second analysis signal to keep time synchronization with the reproduction signal; s5, mixing the second analytic signal and outputting a zero intermediate frequency signal; s6, performing conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal; s7, filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal; s8, keeping time synchronization of the Doppler frequency preliminary estimation value and the low-frequency phase difference signal; s9, converting to obtain a complex signal, and obtaining an accurate estimated value of Doppler signal frequency according to the complex signal to realize accurate measurement of the detector.
Description
Technical Field
The application relates to the technical field of deep space exploration, in particular to a method and a device for improving the measurement precision of a detector.
Background
The radio communication of the detector mainly comprises an uplink and a downlink, is mainly used for the measurement and control of the detector and the downloading of load data, and can be used for the research of radio science by measuring downlink signals, the position and speed signals of the detector can be obtained through radio ranging and Doppler frequency shift speed measurement, the method is a common means for realizing the orbit determination of a spacecraft, and the research of planetary science can be carried out by utilizing the amplitude, doppler frequency, polarization characteristics and the like of radio waves measured by the downlink signals. Tracking of the probe by the station can be divided into single, double and triple modes according to the form of uplink and downlink, and into closed and open modes according to whether the link is closed. In order to meet the requirements of high-precision orbit determination and planetary radio scientific research, high requirements are put on the measurement precision of Doppler frequency, for downlink signals, the transmission power of data transmission signals is generally far greater than the power of measurement and control beacons, so that the higher Doppler measurement precision can be obtained theoretically by adopting the data transmission signals, for a two-way mode, the measurement of carrier frequency can be realized by a coherent integration mode because the downlink signals are completely known, compared with a one-way mode and a three-way mode, the measurement of carrier frequency is realized by adopting a Kestes loop mainly because the data transmission downlink signals are unknown, and the signal-to-noise ratio is deteriorated because of the nonlinearity of square operation, the self-multiplication of noise and the cross term of noise signals of the Kestes loop, and particularly, the noise variance is increased sharply under the condition of low signal-to-noise ratio, so that the Doppler estimation precision is seriously reduced.
Disclosure of Invention
First, the technical problem to be solved
Based on the problems, the application provides a method and a device for improving the measuring precision of a detector, which are used for analyzing, reproducing, filtering and other operations on Doppler signals of the detector based on Doppler frequency shift to realize the accurate estimation of the Doppler signals, so as to improve the measuring precision of the detector.
(II) technical scheme
In a first aspect, the present application provides a method for improving measurement accuracy of a detector, where the detector measures based on doppler shift, the detector sends a detection signal, the detection signal is received by a ground antenna after being transmitted, and the detection signal generates doppler shift due to a relative speed between the detector and the ground antenna, so as to obtain a doppler signal, the method includes: s1, converting Doppler signals into analysis signals, and dividing the analysis signals into two paths, namely a first analysis signal and a second analysis signal; s2, demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value; s3, realizing reproduction of the detection signal according to the demodulation data and the mode of the detection signal, and generating a reproduction signal; s4, compensating the second analysis signal according to the signal delay of demodulation and signal reproduction so as to enable the second analysis signal to keep time synchronization with the reproduction signal; s5, mixing the second analysis signal obtained in the step S4, and outputting a zero intermediate frequency signal; s6, performing conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal; s7, filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal; s8, keeping time synchronization of the Doppler frequency preliminary estimation value and the low-frequency phase difference signal; s9, transforming by using the low-frequency phase difference signal and the Doppler frequency preliminary estimated value output in the step S2 to obtain a complex signal, and obtaining the accurate estimated value of the carrier phase of the detection signal and the Doppler signal frequency according to the complex signal, thereby realizing the accurate measurement of the detector.
Optionally, step S5 specifically includes: and (3) mixing the second analysis signal obtained in the step (S4) with the complex signal obtained in the step (S9) and outputting a zero intermediate frequency signal.
Optionally, step S1 includes: s11, converting Doppler signals into digital signals; s12, converting the digital signal into an analysis signal.
Optionally, step S11 further includes: s0, amplifying the Doppler signal and converting the Doppler signal into an intermediate frequency Doppler signal.
Optionally, the method further includes a preset frequency standard signal, and the step S11 specifically includes: the Doppler signal is converted into a digital signal according to the frequency standard signal.
Optionally, step S7 specifically includes: and integrating the signal phase difference signal to improve the signal-to-noise ratio of the signal phase difference signal, filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal.
In a second aspect, the present application provides a device for improving measurement accuracy of a detector, where the detector measures based on doppler shift, the detector emits a detection signal, and the detection signal is reflected to obtain a doppler signal, the device comprising: the conversion module is used for converting the Doppler signal into an analysis signal and dividing the analysis signal into two paths, namely a first analysis signal and a second analysis signal; the demodulation module is used for demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value; the signal reproduction module is used for realizing reproduction of the detection signal according to the demodulation data and the mode of the detection signal and generating a reproduction signal; a first time delay module for compensating the second resolved signal according to the signal delay of demodulation and signal reproduction so as to keep the second resolved signal in time synchronization with the reproduction signal; the frequency mixing module is used for mixing the second analytic signal obtained by the first time delay module and outputting a zero intermediate frequency signal; the conjugate multiplication module is used for carrying out conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal; the loop filtering module is used for filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal; the second time delay module is used for keeping the Doppler frequency preliminary estimated value and the low-frequency phase difference signal in time synchronization; the digital control oscillator module is used for transforming the Doppler frequency preliminary estimated value output by the low-frequency phase difference signal and the second time delay module to obtain a complex signal, and obtaining the accurate estimated value of the carrier phase of the detection signal and the Doppler signal frequency according to the complex signal so as to realize the accurate measurement of the detector.
Optionally, the conversion module includes an analog-to-digital conversion sub-module and an analytic signal conversion sub-module, wherein: the analog-to-digital conversion sub-module is used for converting the Doppler signal into a digital signal; and the analytic signal conversion sub-module is used for converting the digital signal into an analytic signal.
Optionally, the Doppler signal is input into the low-noise amplifying module for amplifying before being input into the converting module, and is input into the down-converting module for converting into an intermediate-frequency Doppler signal.
Optionally, the device further comprises an atomic clock module and a frequency synthesizer module, wherein: an atomic clock module for providing a 10MHz frequency standard and a 1pps signal; the frequency synthesizer module is used for outputting a preset frequency standard signal with the same frequency as the 10MHz frequency standard provided by the atomic clock module, so that the down-conversion module and the analog-digital conversion sub-module take the preset frequency standard signal as the frequency standard.
(III) beneficial effects
The application provides a method and a device for improving the measurement precision of a detector, which can overcome the problem of the reduction of the Doppler estimation precision caused by the square effect due to the coherence characteristic of noise in a Kestes loop in the traditional method by analyzing, reproducing, filtering and the like the received Doppler frequency shift signal. The method converts noise coherence into incoherent correlation, and can obviously improve Doppler estimation precision, thereby obviously improving the estimation precision of the detector orbit and the research application effect of planetary radio science, and especially has more obvious effect under the condition of low signal-to-noise ratio for deep space detection.
Drawings
FIG. 1 schematically illustrates a step diagram of a method of improving the accuracy of a detector measurement in an embodiment of the present disclosure;
FIG. 2 schematically illustrates an operational flow diagram of an apparatus for improving the accuracy of a detector measurement in accordance with an embodiment of the present disclosure;
FIG. 3 schematically illustrates a flow chart of operation of a demodulation module in the apparatus for improving measurement accuracy of a detector shown in FIG. 2 in accordance with an embodiment of the present disclosure;
fig. 4 schematically illustrates a comparison of a method for improving the measurement accuracy of a detector according to an embodiment of the present disclosure with a measurement accuracy obtained by a conventional costas loop method.
Detailed Description
The present application will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present application more apparent.
In a first aspect, the present application provides a method for improving measurement accuracy of a detector, where the detector performs measurement based on doppler shift, the detector sends a detection signal, the detection signal is received by a ground antenna after being transmitted, and the signal generates doppler shift due to a relative speed between the detector and a receiving antenna, referring to fig. 1, where the method includes: s1, converting Doppler signals into analysis signals, and dividing the analysis signals into two paths, namely a first analysis signal and a second analysis signal; s2, demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value; s3, realizing reproduction of the detection signal according to the demodulation data and the mode of the detection signal, and generating a reproduction signal; s4, compensating the second analysis signal according to the signal delay of demodulation and signal reproduction so as to enable the second analysis signal to keep time synchronization with the reproduction signal; s5, mixing the second analysis signal obtained in the step S4, and outputting a zero intermediate frequency signal; s6, performing conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal; s7, filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal; s8, keeping time synchronization of the Doppler frequency preliminary estimation value and the low-frequency phase difference signal; s9, transforming by using the low-frequency phase difference signal and the Doppler frequency preliminary estimated value output in the step S2 to obtain a complex signal, and obtaining an accurate estimated value of the Doppler signal frequency according to the complex signal so as to realize accurate measurement of the detector. The method will be described in detail below by taking a specific example.
S1, converting Doppler signals into analysis signals, and dividing the analysis signals into two paths, namely a first analysis signal and a second analysis signal;
specifically, after receiving the doppler signal, the doppler signal is first input to a low noise amplifier or the like to amplify, and the amplified signal is input to a down converter to be converted into an intermediate frequency doppler signal, and then the following steps S11 and S22 are executed, specifically:
s11, converting Doppler signals into digital signals;
specifically, the intermediate frequency Doppler signal is converted into a digital signal by digital-to-analog conversion (ADC) of the ADC.
S12, converting the digital signal into an analysis signal.
The digital sampling signal is converted into an analytic complex signal by an analytic signal conversion module and the like, and the specific implementation can be performed by adopting a Hilbert transform or quadrature sampling mode, and in the embodiment of the application, if the digital signal is x (t), the converted analytic signal z (t) is:
wherein, the liquid crystal display device comprises a liquid crystal display device,hilbert transform for x (t), t being a time series;
for narrowband signals, the resolved signal z (t) can be expressed as:
wherein f c Is the carrier frequency after down-conversion; phi is the initial phase; j is an imaginary unit; a (t) is a modulation signal,wherein a (nT) c ) Is a binary sequence, n is a sequence number, T c Q (t) is a rectangular window function for the chip width, for the BPSK signal
a(nT c )＝±1
And dividing the generated analytic signal into two paths of identical signals, namely a first analytic signal and a second analytic signal.
S2, demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value;
and (2) demodulating the first analysis signal output in the step (S1) to obtain information carried by the first analysis signal, and outputting demodulation data and a Doppler frequency preliminary estimated value.
In the embodiment of the application, the z (t) signal is demodulated to obtain a demodulated binary sequence a (n)T c )。
S3, realizing reproduction of the detection signal according to the demodulation data and the mode of the detection signal, and generating a reproduction signal;
and reproducing the detection signal transmitted by the detector according to the demodulation data and the mode of the detection signal transmitted by the detector, namely regenerating a continuous signal.
In the embodiment of the application, according to the input demodulated sequence a (nT c ) The method realizes the reproduction of the downlink data transmission signal, namely the detection signal, which is the reproduction signal:
wherein f p The intermediate frequency obtained by subtracting the down-conversion reference frequency from the theoretical emission frequency of the detector is free from the influence of Doppler frequency; phi (phi) p An initial phase of the probe signal; τ p Is the time delay due to demodulation and signal reproduction.
S4, compensating the second analysis signal according to the signal delay of demodulation and signal reproduction so as to enable the second analysis signal to keep time synchronization with the reproduction signal;
when processing the second analysis signal, it is necessary to refer to the signal delay of demodulation and signal reproduction in the above steps S2 to S3, and compensate the second analysis signal according to the signal delay of demodulation and signal reproduction so as to keep the second analysis signal time-synchronized with the reproduction signal.
In the embodiment of the present application, the compensated second analytic signal may be expressed as:
wherein phi is the initial phase.
S5, mixing the second analysis signal obtained in the step S4, and outputting a zero intermediate frequency signal;
the method is closed-loop control, and mixes the second analysis signal obtained in the step S4 with the complex signal obtained in the following step S9 to output a zero intermediate frequency signal.
In the embodiment of the present application, if the output complex signal obtained in step S9 is:
wherein f d For accurate estimation of the measured Doppler frequency, phi d For detecting carrier phase measurements in the signal. The mixed zero intermediate frequency signal z 2 (t) is:
wherein, the liquid crystal display device comprises a liquid crystal display device,is z d Conjugation of (t).
S6, performing conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal;
and (3) performing conjugate multiplication on the zero intermediate frequency signal obtained in the step (S6) and the reproduction signal obtained in the step (S3) to obtain a phase difference signal.
In the embodiment of the application, the mixed signal z 2 And (t) the phase difference signal output after conjugate multiplication is:
wherein Δf=f c -f d -f p ，Δφ＝φ-φ d -φ p -2πf c τ p +2πf p τ p 。
As can be seen from the above, when the signal frequency f is outputted in step S9 d And phase phi d Satisfies the following condition f d ＝f c -f p And phi d ＝φ-φ p -2πf c τ p +2πf p τ p When γ (t) =a can be obtained 2 (t-τ p ) Thereby realizing the phase of the phase difference signal gamma (t) as 0 and realizing the ideal estimation of Doppler frequency side. However, in practical situations, due to the influence of noise, the γ (t) needs to be processed through operations such as integration and filtering, so as to remove high-frequency components and noise in the phase difference signal, and improve the signal-to-noise ratio.
S7, filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal;
integrating the phase difference signals to improve the signal to noise ratio, filtering out high-frequency noise of the phase difference signals and outputting low-frequency phase difference signals. This step may be implemented using a general loop filter.
S8, keeping time synchronization of the Doppler frequency preliminary estimation value and the low-frequency phase difference signal;
and (3) carrying out time delay on the Doppler frequency preliminary estimated value obtained in the step (S2) so as to enable the Doppler frequency preliminary estimated value to be in time synchronization with the low-frequency phase difference signal obtained in the step (S7).
S9, transforming by using the low-frequency phase difference signal and the Doppler frequency preliminary estimated value output by the step S2 module to obtain a complex signal, and obtaining the accurate estimated value of the carrier phase of the detection signal and the Doppler signal frequency according to the complex signal, thereby realizing the accurate measurement of the detector. The specific implementation method is as follows:
accumulating the phase of the low frequency phase difference signal to the output complex signal of step S9, namely:
wherein z is d (t m ) At t m Step S9 of moment outputs the complex signal to the mixer; z d (t m ) Its initial value z d (t 0 ) Adopting the Doppler frequency preliminary estimated value output by the step S2 module; phi (phi) γ (t m ) Is gamma (t) and is subjected to loop filtering and then is at t m The phase of the moment; m is a sampling point sequence number, and m=0, 1,2, …; t is t m Is a time series.
If signal z d (t m ) Is of the phase ofThe least squares estimation of the doppler frequency and the initial phase of the carrier is then:
in the method, in the process of the application,is a parameter vector with identification, A is a coefficient matrix, b is a carrier phase difference observation vector, and
wherein f d For accurate estimation of the measured Doppler frequency, phi d For detecting carrier phase measurements in the signal. The above equation only gives a linear estimation model of Doppler frequency, and a secondary or higher estimation model can be adopted in practical application according to the Doppler dynamic change degree.
In another aspect, the present application provides a device for improving measurement accuracy of a detector, where the detector measures based on doppler shift, the detector emits a detection signal, and the detection signal is reflected to obtain a doppler signal, as shown in fig. 2, where the device includes:
the conversion module is used for converting the Doppler signal into an analysis signal and dividing the analysis signal into two paths, namely a first analysis signal and a second analysis signal;
the conversion module includes an analog-to-digital conversion sub-module (ADC) and an analytic signal conversion sub-module, wherein:
the analog-to-digital conversion sub-module is used for converting the Doppler signal into a digital signal;
and the analytic signal conversion sub-module is used for converting the digital signal into an analytic signal.
In the embodiment of the application, the analysis signal conversion submodule realizes conversion from a digital signal to an analysis signal, and specifically can adopt a Hilbert transformation or quadrature sampling mode, and in the embodiment of the application, if the digital signal after being subjected to analog-to-digital conversion submodule (ADC) is x (t), the analysis signal after being subjected to conversion by the analysis signal conversion submodule is:
wherein, the liquid crystal display device comprises a liquid crystal display device,hilbert transform for x (t), t being a time series;
for narrowband signals, the resolved signal may be expressed as:
wherein f c Is the carrier frequency after down-conversion; a (t) is a modulation signal,wherein a (nT) c ) Is a binary sequence, n is a sequence number, T c Q (t) is a rectangular window function for the chip width, for the BPSK signal
a(nT c )＝±1
And dividing the generated analytic signal into two paths of identical signals, namely a first analytic signal and a second analytic signal.
The demodulation module is used for demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value;
the demodulation module demodulates the z (t) signal to obtain a demodulated binary sequence a (nT) c ). As shown in fig. 3, the demodulation module is composed of a matched filtering module, a timing synchronization module, a frequency acquisition module, a carrier synchronization module, a symbol discrimination module and the like. FIG. 2 is a schematic diagram of a data processing flow of a demodulation module of the present application, after a signal is matched and filtered to raise a signal to noise ratio, an output signal is sent to a frequency capturing and timing synchronization module to complete Doppler frequency offset estimation and symbol synchronization, respectively; the frequency acquisition module obtains Doppler frequency initial values as search initial values of the carrier synchronization module; the carrier synchronization module adopts a carrier locking mode based on a Kestes ring to realize locking of carrier phases; the Doppler frequency shift value obtained by tracking the carrier synchronization module is output to a digital control oscillator module (NCO) module after practical delay to be used as an initial value of Doppler frequency, and the output in-phase signal is subjected to a symbol discrimination module to obtain a demodulated binary sequence a (nT) c )。
The signal reproduction module is used for realizing reproduction of the detection signal according to the demodulation data and the mode of the detection signal and generating a reproduction signal;
the signal reproduction module generates a signal based on the input demodulated sequence a (nT c ) The method realizes the reproduction of the downlink data transmission signal, namely the detection signal, which is the reproduction signal:
wherein f p The intermediate frequency obtained by subtracting the down-conversion reference frequency from the theoretical emission frequency of the detector is free from the influence of Doppler frequency; phi (phi) p Is the initial phase of the transmitted signal; τ p Is the time delay due to demodulation and signal reproduction.
The first time delay module is used for compensating the second analysis signal according to the signal delay of demodulation and signal reproduction so as to keep the second analysis signal in time synchronization with the reproduction signal;
in the embodiment of the present application, the second analysis signal compensated by the first time delay module may be expressed as:
wherein phi is the initial phase.
The frequency mixing module is used for mixing the second analytic signal obtained by the first time delay module and outputting a zero intermediate frequency signal;
if the complex signal output by the numerically controlled oscillator module (NCO) to the mixing module is:
wherein f d For accurate estimation of the measured Doppler frequency, phi d For detecting carrier phase measurements in the signal. The zero intermediate frequency signal after mixing by the mixing module is:
the conjugate multiplication module is used for carrying out conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal;
in the embodiment of the application, the signal z after being mixed by the mixing module 2 And (t) the phase difference signal output after conjugate multiplication is:
wherein Δf=f c -f d -f p ，Δφ＝φ-φ d -φ p -2πf c τ p +2πf p τ p 。
As can be seen from the above, when the NCO outputs a signal of frequency f d And phase phi d Satisfies the following condition f d ＝f c -f p And phi d ＝φ-φ p -2πf c τ p +2πf p τ p When γ (t) =a can be obtained 2 (t-τ p ) Thereby realizing the phase of the phase difference signal gamma (t) as 0 and realizing the ideal estimation of Doppler frequency. However, in practical situations, due to the influence of noise, the γ (t) needs to be processed through operations such as integration and filtering, so as to remove high-frequency components and noise in the phase difference signal, and improve the signal-to-noise ratio.
The loop filtering module is used for filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal;
the loop filter may be a linear loop filter common to phase locked loops, the output signal of which is used to achieve closed loop control of the NCO output signal.
The second time delay module is used for keeping the preliminary Doppler frequency estimated value and the low-frequency phase difference signal in time synchronization;
the digital control oscillator module is used for obtaining a complex signal by utilizing the low-frequency phase difference signal and the Doppler frequency preliminary estimated value output by the second time delay module, obtaining an accurate estimated value of the Doppler signal frequency according to the complex signal, and further realizing the accurate measurement of the detector.
Adding the phase of the low frequency phase difference signal to the complex signal output by the NCO module, namely:
wherein z is d (t m ) At t m The NCO of the moment outputs the complex signal to the mixer; z d (t m ) Initial value z d (t 0 ) Preliminary Doppler frequency estimation values are adopted; phi (phi) γ (t m ) Is gamma (t) and is subjected to loop filtering and then is at t m The phase of the moment; m is a sampling point sequence number, and m=0, 1,2, …; t is t m Is a time series.
If signal z d (t m ) Is of the phase ofThe least squares estimation of the doppler frequency and the initial phase of the carrier is then:
in the method, in the process of the application,is a parameter vector with identification, A is a coefficient matrix, b is a carrier phase difference observation vector, and
wherein f d For accurate estimation of the measured Doppler frequency, phi d For detecting carrier phase measurements in the signal. The above equation only gives a linear estimation model of Doppler frequency, and a secondary or higher estimation model can be adopted in practical application according to the Doppler dynamic change degree.
The device also comprises a noise amplification module, a down-conversion module, an atomic clock module and a frequency synthesizer module, wherein Doppler signals are input into the low-noise amplification module for amplification before being input into the conversion module and are input into the down-conversion module for frequency conversion into intermediate-frequency Doppler signals; an atomic clock module for providing a 10MHz frequency standard and a 1pps signal; the frequency synthesizer module is used for outputting a preset frequency standard signal with the same frequency as the 10MHz frequency standard provided by the atomic clock module, so that the down-conversion module and the analog-digital conversion sub-module take the preset frequency standard signal as the frequency standard.
Fig. 4 is a schematic diagram comparing the signal-to-noise ratio of the doppler estimation of the conventional method and the method disclosed in the present application.
The conventional Doppler frequency measurement error based on the Kestus loop can be expressed as
Wherein SNR is i For signal-to-noise ratio of input signal, B i For input signal bandwidth, B L Is the noise bandwidth of the phase-locked loop, lambda is the signal wavelength, T c Is the code bit width. In the Doppler measurement method provided by the application, the coherent integration of signals is realized, so that the Doppler frequency measurement error can be expressed as follows:
for BPSK signals, the doppler measurement error based on the costas loop and the new method is shown in fig. 4 at a code rate of 1 Mbps. It can be seen that the new method is significantly lower than the measurement error of the costas loop under the condition of equal signal-to-noise ratio.
While the foregoing is directed to embodiments of the present application, other and further details of the application may be had by the present application, it should be understood that the foregoing description is merely illustrative of the present application and that no limitations are intended to the scope of the application, except insofar as modifications, equivalents, improvements or modifications are within the spirit and principles of the application.
Claims (10)
1. A method for improving measurement accuracy of a detector, the detector performing measurement based on doppler shift, the detector sending a detection signal, the detection signal being received by a ground antenna after being transmitted, the detection signal generating doppler shift due to a relative speed between the detector and the ground antenna, and obtaining a doppler signal, the method comprising:
s1, converting the Doppler signal into an analysis signal, and dividing the analysis signal into two paths, namely a first analysis signal and a second analysis signal;
s2, demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value;
s3, realizing reproduction of the detection signal according to the demodulation data and the mode of the detection signal, and generating a reproduction signal;
s4, compensating the second analysis signal according to the signal delay of demodulation and signal reproduction so as to enable the second analysis signal to keep time synchronization with the reproduction signal;
s5, mixing the second analysis signal obtained in the step S4, and outputting a zero intermediate frequency signal;
s6, performing conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal;
s7, filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal;
s8, the Doppler frequency preliminary estimated value and the low-frequency phase difference signal are kept in time synchronization;
s9, transforming by using the low-frequency phase difference signal and the Doppler frequency preliminary estimated value output in the step S2 to obtain a complex signal, and obtaining an accurate estimated value of the carrier phase of the detection signal and the Doppler signal frequency according to the complex signal, thereby realizing accurate measurement of the detector.
2. The method according to claim 1, wherein the step S5 specifically comprises:
and (3) mixing the second analysis signal obtained in the step (S4) with the complex signal obtained in the step (S9) and outputting a zero intermediate frequency signal.
3. The method according to claim 1, said step S1 comprising:
s11, converting the Doppler signal into a digital signal;
s12, converting the digital signal into an analysis signal.
4. A method according to claim 3, said step S11 further comprising, prior to:
s0, amplifying the Doppler signal and converting the Doppler signal into an intermediate frequency Doppler signal.
5. A method according to claim 3, further comprising presetting a frequency standard signal, said step S11 being specifically:
and converting the Doppler signal into a digital signal according to the frequency standard signal.
6. The method according to claim 1, wherein the step S7 is specifically:
and integrating the phase difference signal to improve the signal-to-noise ratio of the phase difference signal, filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal.
7. An apparatus for improving measurement accuracy of a detector, the detector measuring based on doppler shift, the detector emitting a detection signal, the detection signal being reflected to obtain a doppler signal, the apparatus comprising:
the conversion module is used for converting the Doppler signal into an analysis signal and dividing the analysis signal into two paths, namely a first analysis signal and a second analysis signal;
the demodulation module is used for demodulating the first analytic signal to obtain demodulation data and a Doppler frequency preliminary estimated value;
the signal reproduction module is used for realizing reproduction of the detection signal according to the demodulation data and the mode of the detection signal and generating a reproduction signal;
a first time delay module for compensating the second resolved signal according to the signal delay of demodulation and signal reproduction so as to keep the second resolved signal in time synchronization with the reproduction signal;
the frequency mixing module is used for mixing the second analytic signal obtained by the first time delay module and outputting a zero intermediate frequency signal;
the conjugate multiplication module is used for carrying out conjugate multiplication on the zero intermediate frequency signal and the reproduction signal to obtain a phase difference signal;
the loop filtering module is used for filtering high-frequency noise of the phase difference signal and outputting a low-frequency phase difference signal;
the second time delay module is used for keeping the Doppler frequency preliminary estimated value and the low-frequency phase difference signal in time synchronization;
the digital control oscillator module is used for transforming the low-frequency phase difference signal and the Doppler frequency preliminary estimated value output by the second time delay module to obtain a complex signal, and obtaining the accurate estimated value of the carrier phase of the detection signal and the Doppler signal frequency according to the complex signal so as to realize the accurate measurement of the detector.
8. The apparatus of claim 7, the conversion module comprising an analog-to-digital conversion sub-module and a analytic signal conversion sub-module, wherein:
the analog-to-digital conversion sub-module is used for converting the Doppler signal into a digital signal;
and the analytic signal conversion sub-module is used for converting the digital signal into an analytic signal.
9. The apparatus of claim 8, further comprising a low noise amplification module and a down conversion module, the doppler signal being input to the low noise amplification module for amplification before being input to the conversion module and being input to the down conversion module for frequency conversion to an intermediate frequency doppler signal.
10. The apparatus of claim 9, further comprising an atomic clock module and a frequency synthesizer module, wherein:
an atomic clock module for providing a 10MHz frequency standard and a 1pps signal;
and the frequency synthesizer module is used for outputting a preset frequency standard signal with the same frequency as the frequency standard of 10MHz provided by the atomic clock module, so that the down-conversion module and the analog-digital conversion submodule take the preset frequency standard signal as the frequency standard.
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