CN109839623B - Method for processing range finding of radar surface target echo signal for extraterrestrial celestial body landing measurement - Google Patents

Method for processing range finding of radar surface target echo signal for extraterrestrial celestial body landing measurement Download PDF

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CN109839623B
CN109839623B CN201910113891.4A CN201910113891A CN109839623B CN 109839623 B CN109839623 B CN 109839623B CN 201910113891 A CN201910113891 A CN 201910113891A CN 109839623 B CN109839623 B CN 109839623B
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孙武
蒋清富
徐秋锋
贾学振
吴堃
柯腾伦
丁凯生
陈枭煜
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Beijing Institute of Remote Sensing Equipment
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Abstract

The invention provides a method for processing the distance measurement of an echo signal of a radar surface for measuring the landing of an extraterrestrial celestial body, wherein an intermediate frequency echo (1) is preprocessed (5) and comprises A/D sampling (2), demodulation filtering extraction (3) and FFT (4); the range capture channel (8) processing comprises capturing a CFAR (6) and capturing an echo center calculation (7), thereby obtaining an echo main lobe center position (17); the ranging tracking channel (16) processing comprises tracking wave gate interception (10), tracking CFAR (11), tracking echo center calculation (12), main lobe interception (13) and OCOG (14), so that the gravity center position (18) is obtained to extract ranging information. The capture channel and the tracking channel are cooperatively processed to reduce the influence of a wild value in the measuring process, the influence of burrs of the echo can be avoided through the tracking channel, the tracking is stabilized in the tracking interception threshold, the effective measurement of the target echo of the extraterrestrial celestial body surface is realized, and the processing speed and the ranging stability are improved.

Description

Method for processing range finding of radar surface target echo signal for extraterrestrial celestial body landing measurement
Technical Field
The invention relates to the technical field of surface target echo processing, in particular to a radar surface target echo signal distance measurement processing method for extraterrestrial celestial body landing measurement.
Background
The trajectory characteristics of landers require that the landing radar be able to measure the distance to which different beams are directed. The traditional altimeter extracts the front edge of an echo to calculate the vertical distance according to the echo characteristic of the vertical incidence of the wave beam; unlike a traditional altimeter, the landing radar ranging algorithm must take account of the echo characteristics of both vertical incidence and oblique incidence. The wave beam emitted by the antenna has a certain width, the antenna wave beam irradiates a region in the descending process of the lander, the radial distance between the antenna wave beam and each scattering point of an irradiated surface is different, and components with different delays are mutually superposed to form an echo signal received by the radar. The method is characterized in that the slope distance value of an echo is required to be accurately extracted by a surface target echo processing algorithm, the main point is to reduce the influence of severe fluctuation of a main lobe waveform caused by surface target echo vector superposition to the maximum extent, and the gravity center of the echo main lobe is accurately extracted.
Disclosure of Invention
Therefore, the invention provides a radar surface target echo signal processing method for the landing measurement of an extraterrestrial celestial body, which can solve the problem that the traditional sea surface echo processing algorithm cannot be effectively applied to the landing surface target processing, extracts the central position and the gravity center position of a main lobe, calculates a capture value and a tracking value and reduces the condition that the tracking is lost due to the occurrence of echo burrs.
The method for processing the range finding of the radar surface target echo signal for the extraterrestrial celestial body landing measurement is used for extracting the central position and the gravity center position of a surface target echo main lobe.
The method comprises the following steps: preprocessing intermediate frequency echoes, which comprises A/D sampling, demodulation filtering extraction and FFT; the distance measurement and capture channel comprises a CFAR capture channel and an echo center capture channel, so that the central position of the main lobe of the echo is obtained; the tracking channel comprises tracking wave gate interception, tracking CFAR, tracking echo center calculation, main lobe interception and OCOG, so that the gravity center position is obtained to extract ranging information.
The intermediate frequency echo is preprocessed, and a radar receiving signal formula after A/D sampling is as follows:
Figure BDA0001969371710000011
wherein: t is time, TdFor delay of received signal relative to transmitted signal, PrFor receiving signal power, omega0Is the center angle of the linear frequency modulationFrequency, fdIs the frequency of the doppler frequency and is,
Figure BDA0001969371710000021
in order to transmit the initial phase of the signal,
Figure BDA0001969371710000022
for the initial phase of the received signal, NTzqIs the Nth frequency modulation period; k is the frequency modulation slope,
Figure BDA0001969371710000023
for modulating bandwidth, TM5ms is a frequency modulation period;
performing decimation filtering on the radar receiving signals after A/D sampling, and demodulating the data after decimation filtering, wherein a demodulation formula is as follows:
Figure BDA0001969371710000024
wherein
Figure BDA0001969371710000025
In order to demodulate the signal for a positive frequency modulation,
Figure BDA0001969371710000026
is a positive frequency modulated received signal;
and (3) demodulating a real part signal:
Figure BDA0001969371710000027
demodulating the imaginary signal:
Figure BDA0001969371710000028
filtering the demodulated signal, the filtered signal:
Figure BDA0001969371710000029
Figure BDA0001969371710000031
the negative frequency modulation extraction filtering and demodulation filtering processing is the same as the positive frequency modulation processing method, and the signals after the negative frequency modulation demodulation filtering are obtained:
Figure BDA0001969371710000032
n is respectively carried out on positive frequency modulation echo signals and negative frequency modulation echo signalsFFTPoint FFT processing
Figure BDA0001969371710000033
Figure BDA0001969371710000034
The ranging acquisition channel comprises acquisition CFAR and acquisition echo center calculation;
adopting capture CFAR detection for the signals after FFT processing, and judging that echo signals exist if the peak signals exceed a detection threshold after the peak signals are detected; wherein the detection threshold for capturing CFAR is defined as NCFAR_n×Pn，4≤NCFAR_n≤10，PnCarrying out sectional statistics on noise on the signal amplitude after FFT processing for the noise amplitude, and taking the noise statistical result with the minimum mean value as the noise amplitude after respectively solving the mean value;
the method comprises the following steps of acquiring the center of an echo, calculating, opening a window by taking a signal peak value after FFT processing as a center, detecting an amplitude value exceeding a threshold, and calculating the center of the echo, wherein the operation is as follows:
the peak value of the detection window is taken as the center, and the left width and the right width are w1And w2Detecting whether the amplitude exceeds a threshold hsA point of (1), wherein w1＝wid×γ1，w2＝wid×γ2，wid＝fp×α, wherein 0.15- α -0.3, fpThe absolute value of the frequency corresponding to the amplitude value exceeding the threshold is determined, if the absolute value is a positive slopeWave of
Figure BDA0001969371710000035
Figure BDA0001969371710000036
If it is a negative slope echo, then
Figure BDA0001969371710000037
Threshold hs＝Ap/Np，
Figure BDA0001969371710000038
Wherein A ispIs the amplitude of the peak;
extracting 10 signals with maximum amplitude from the detected signals meeting the threshold, weighting the corresponding frequency and amplitude to obtain a frequency spectrum position, and taking the frequency spectrum position as the center f of the intercepted echorWherein A isnAnd fnRespectively, the amplitude and the spectral position corresponding to each point;
Figure BDA0001969371710000041
will f isr +And fr -Respectively as the centers of the gates of positive and negative frequency modulation;
wherein the capture distance RcThe calculation formula is as follows:
Figure BDA0001969371710000042
wherein f issFor the decimated signal sample rate, c is the speed of light.
The tracking channel comprises tracking wave gate interception, tracking CFAR, tracking echo center calculation, main lobe interception and OCOG, so that the gravity center position is obtained to extract ranging information:
the tracking channel is connected with the tracking channel enable under the condition of ranging, if the tracking is not started yet, but the acquisition channel obtains an effective acquisition distance, the tracking is started in the next period, and the period has the following stepsEffective capture distance RcTrace recursion data R as next cycletrack；
Tracking the recursion data R according to the distance of the previous periodtrackAnd velocity tracking recurrence data vtrackSetting the center and width of a tracking wave gate;
tracking wave gate center with negative frequency modulation
Figure BDA0001969371710000043
Figure BDA0001969371710000044
Wherein, λ is the carrier wavelength of speed measurement.
Tracking wave gate center with positive frequency modulation
Figure BDA0001969371710000045
Figure BDA0001969371710000046
Figure BDA0001969371710000051
Tracking wave gate center WgzN of distance tracking recursion data with tracking gate width of last cyclebm0.15 or less of Nbm≤0.3：
Figure BDA0001969371710000052
According to the left side of the interception center during negative frequency modulation interception
Figure BDA0001969371710000053
Right side of the
Figure BDA0001969371710000054
Intercepting in proportion;
according to the left side of the interception center during positive frequency modulation interception
Figure BDA0001969371710000055
Right side of the
Figure BDA0001969371710000056
Intercepting in proportion;
adopting tracking CFAR detection for the signals after FFT processing, and judging that echo signals exist if the peak signals exceed a detection threshold after the peak signals are detected; wherein the tracking CFAR detection threshold is defined as NCFAR_n×Pn；
Tracking the center of the echo, calculating a window by taking the peak value of the signal after FFT processing as the center, detecting the amplitude value exceeding the threshold, and calculating the center of the echo, wherein the operation is as follows:
the peak value of the detection window is taken as the center, and the left width and the right width are w1And w2Detecting whether the amplitude exceeds a threshold hsA point of (1), wherein w1＝wid×γ1，w2＝wid×γ2，wid＝fp×α, if it is a positive slope echo
Figure BDA0001969371710000057
If it is a negative slope echo, then
Figure BDA0001969371710000058
Extracting 10 signals with maximum amplitude from the detected signals meeting the threshold, weighting the corresponding frequency and amplitude to obtain a frequency spectrum position, and taking the frequency spectrum position as the center f of the intercepted echorWherein A isnAnd fnRespectively, the amplitude and the spectral position corresponding to each point;
Figure BDA0001969371710000059
will be provided with
Figure BDA00019693717100000510
And
Figure BDA00019693717100000511
respectively as the central positions of the tracking wave gates of the positive frequency modulation and the negative frequency modulation;
the main lobe interception is based on the echo center position output by the CFAR, and the echo with the designated width is intercepted on the main lobe interception, wherein the width W iszx：
Figure BDA0001969371710000061
Wherein N is more than or equal to 0.5zp≤0.9；
According to the left side of the interception center during negative frequency modulation interception
Figure BDA0001969371710000062
Right side of the
Figure BDA0001969371710000063
Intercepting in proportion;
according to the left side of the interception center during positive frequency modulation interception
Figure BDA0001969371710000064
Right side of the
Figure BDA0001969371710000065
Intercepting in proportion;
and in the intercepted main lobe width, secondarily judging and intercepting the main lobe, wherein the judging conditions are as follows:
the amplitude of the signal in the main lobe exceeds a threshold, which is Nocog_n×Pn，2≤Nocog_nLess than or equal to 4; searching from the center of the wave gate to the left and right sides respectively if N is continuouslxIf the point signal amplitude does not exceed the threshold, the lower limit/upper limit of the main lobe is cut off, wherein N is more than or equal to 6lx≤20；
Center of gravity estimation value S:
Figure BDA0001969371710000066
wherein:
s[tr(m)]after secondary interceptionThe FFT-processed main lobe signal of (a);
and m is the FFT position point of the main lobe signal after the secondary interception.
The center of gravity of positive frequency modulation in the OCOG is used as
Figure BDA0001969371710000067
Negative frequency-modulated echo center as
Figure BDA0001969371710000068
Tracking distance RtThe calculation formula is as follows:
Figure BDA0001969371710000069
after the tracking is started, the effective tracking distance R of the periodtTrace recursion data R as next cycletrack。
In the invention, the influence of the wild value in the measuring process can be reduced by the cooperative processing of the capturing channel and the tracking channel, because the lander descends and the distance is within a certain dynamic range, the influence of the burr of the echo can be avoided by the tracking channel, and the tracking is stabilized within the tracking interception threshold. Even if a large dynamic condition exists, the distance measurement value can be timely calculated through the capturing channel, and compared with the tracking channel, the tracking can be timely quitted, and the central position of the tracking wave gate is determined again. Therefore, the target echo of the extraterrestrial celestial object surface can be effectively measured, hardware computing resources are reasonably distributed, and the processing speed and the ranging stability are improved.
Drawings
Other characteristics and advantages of the invention will become more apparent in the following detailed description of non-limiting embodiments thereof, with reference to the attached drawings, in which:
fig. 1 is a schematic diagram illustrating a radar surface target echo signal ranging processing method for extraterrestrial celestial body landing surveying according to an embodiment of the present invention.
Description of reference numerals:
1 intermediate frequency echo 2 AD sampling
3 demodulation filtering decimation 4 FFT
5 Pre-treatment 6 Capture CFAR
7 capture echo center calculation 8 capture channel
9 tracking channel enable 10 tracking wave gate intercept
11 tracking CFAR 12 tracking echo center calculation
13 main lobe intercepting 14 OCOG
15 wave gate center and wave gate width 16 tracking channel
17 center position 18 center of gravity position
Detailed description of the preferred embodiment
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the embodiments of the invention and that the invention is not limited thereto. It should be noted that, for convenience of description, only the parts closely related to the embodiments are shown in the drawings. Embodiments may be embodied in many different forms and should not be construed as limited to the forms set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. The same reference numbers in the drawings identify the same or similar elements.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other alternatives. It is to be understood that the block diagrams shown in the figures do not necessarily correspond to physically separate entities.
The invention provides a technical idea for solving the problems of broadening and burr existing in target echoes of a landing surface of an extraterrestrial celestial body, and the technical idea is to process the target echoes of the landing surface of the extraterrestrial celestial body and extract the central position and the gravity center position of a main lobe echo.
As shown in fig. 1, the method for processing the range of the target echo signal of the radar surface for measuring the landing of the extraterrestrial celestial body comprises the following steps:
preprocessing 5 the intermediate frequency echo 1, which comprises A/D sampling 2, demodulation filtering extraction 3 and FFT 4;
the range finding capture channel 8 comprises a capture CFAR6 and a capture echo center calculation 7, resulting in an echo main lobe center position 17;
the range tracking channel 16 includes tracking gate intercept 10, tracking CFAR11, tracking echo center calculation 12, main lobe intercept 13, and OCOG14, resulting in a barycentric location 18 to extract range information.
The following is a detailed description of the method for performing the steps of the preferred embodiment of the present invention:
first, the intermediate frequency echo 1 is preprocessed 5, which includes a/D sampling 2, demodulation filtering decimation 3, and FFT 4.
The radar received signal after a/D sampling 2 is formulated as:
Figure BDA0001969371710000081
wherein: t is time, TdFor delay of received signal relative to transmitted signal, Pr is received signal power, omega0Is the center angular frequency, f, of the linear frequency modulationdIs the frequency of the doppler frequency and is,
Figure BDA0001969371710000082
in order to transmit the initial phase of the signal,
Figure BDA0001969371710000083
for the initial phase of the received signal, NTzqIs the Nth frequency modulation period;
k is the frequency modulation slope,
Figure BDA0001969371710000084
for modulating bandwidth, TM5ms is a frequency modulation period;
performing decimation filtering on the radar receiving signal after the A/D sampling 2, and demodulating the data after the decimation filtering, wherein the demodulation formula is as follows:
Figure BDA0001969371710000091
wherein
Figure BDA0001969371710000092
In order to demodulate the signal for a positive frequency modulation,
Figure BDA0001969371710000093
is a positive frequency modulated received signal;
and (3) demodulating a real part signal:
Figure BDA0001969371710000094
demodulating the imaginary signal:
Figure BDA0001969371710000095
filtering the demodulated signal, the filtered signal:
Figure BDA0001969371710000096
the negative frequency modulation extraction filtering and demodulation filtering processing is the same as the positive frequency modulation processing method, and the signals after the negative frequency modulation demodulation filtering are obtained:
Figure BDA0001969371710000097
n is respectively carried out on positive frequency modulation echo signals and negative frequency modulation echo signalsFFTPoint FFT4 processing
Figure BDA0001969371710000098
Figure BDA0001969371710000101
In the second step, the ranging acquisition channel 8 includes the following specific processes of acquisition CFAR6 and acquisition echo center calculation 7:
the signals processed by the FFT4 are detected by adopting a capture CFAR6, and after peak signals are detected, if the peak signals exceed a detection threshold, echo signals are judged to exist; wherein the detection threshold of the capture CFAR6 is defined as NCFAR_n×Pn，4≤NCFAR_n≤10，PnFor the noise amplitude, noise is calculated in a segmented mode on the signal amplitude processed by the FFT4, and after the noise is respectively averaged, the noise statistical result with the minimum average value is used as the noise amplitude;
the center of the captured echo calculation 7 is operated as follows, a window is opened by taking the peak value of the signal processed by the FFT4 as the center, and the amplitude value exceeding the threshold is detected, thereby calculating the center of the echo:
the peak value of the detection window is taken as the center, and the left width and the right width are w1And w2Detecting whether the amplitude exceeds a threshold hsA point of (1), wherein w1＝wid×γ1，w2＝wid×γ2，wid＝fp×α, wherein 0.15- α -0.3, fpIs the frequency absolute value corresponding to the amplitude value exceeding the threshold, if the amplitude value is a positive slope echo, the frequency absolute value is
Figure BDA0001969371710000102
Figure BDA0001969371710000103
If it is a negative slope echo, then
Figure BDA0001969371710000104
Threshold hs＝Ap/Np，
Figure BDA0001969371710000105
Wherein A ispIs the amplitude of the peak;
extracting 10 signals with maximum amplitude from the detected signals meeting the threshold, and obtaining the signals with maximum amplitudeThe frequency and amplitude corresponding to the frequency and amplitude are weighted to obtain a frequency spectrum position which is taken as the center f of the intercepted echorWherein A isnAnd fnRespectively, the amplitude and the spectral position corresponding to each point;
Figure BDA0001969371710000106
will f isr +And fr -A gate center 15 for positive and negative frequency modulation, respectively;
wherein the capture distance RcThe calculation formula is as follows:
Figure BDA0001969371710000107
Figure BDA0001969371710000111
wherein f issFor the decimated signal sample rate, c is the speed of light.
In the third step, the tracking channel 16 includes tracking gate intercept 10, tracking CFAR11, tracking echo center calculation 12, main lobe intercept 13, and OCOG14, so that obtaining the barycentric location 18 to extract ranging information specifically includes:
the tracking channel 16 is connected with the tracking channel enable 9 in the case of ranging, if the tracking is not started yet, but the acquisition channel 8 obtains the effective acquisition distance, the tracking is started in the next period, and the effective acquisition distance R of the period is usedcTrace recursion data R as next cycletrack；
Tracking the recursion data R according to the distance of the previous periodtrackAnd velocity tracking recurrence data vtrackSetting tracking wave gate center and width 15;
tracking wave gate center with negative frequency modulation
Figure BDA0001969371710000112
Figure BDA0001969371710000113
Wherein, λ is the carrier wavelength of speed measurement.
Tracking wave gate center with positive frequency modulation
Figure BDA0001969371710000114
Figure BDA0001969371710000115
Tracking wave gate center WgzN of distance tracking recursion data with tracking gate width of last cyclebm0.15 or less of Nbm≤0.3：
Figure BDA0001969371710000116
According to the left side of the interception center during negative frequency modulation interception
Figure BDA0001969371710000117
Right side of the
Figure BDA0001969371710000118
Intercepting in proportion;
according to the left side of the interception center during positive frequency modulation interception
Figure BDA0001969371710000119
Right side of the
Figure BDA00019693717100001110
Intercepting in proportion;
the signals processed by the FFT4 are detected by tracking CFAR11, and after peak signals are detected, if the peak signals exceed a detection threshold, echo signals are judged to exist; wherein the tracking CFAR11 detection threshold is defined as NCFAR_n×Pn；
The tracking echo center calculation 12 operates as follows, by opening a window around the peak of the signal processed by the FFT4, detecting an amplitude value exceeding a threshold, and calculating the center of the echo:
the peak value of the detection window is taken as the center, and the left width and the right width are w1And w2Detecting whether the amplitude exceeds a threshold hsA point of (1), wherein w1＝wid×γ1，w2＝wid×γ2，wid＝fp×α, if it is a positive slope echo
Figure BDA0001969371710000121
If it is a negative slope echo, then
Figure BDA0001969371710000122
Extracting 10 signals with maximum amplitude from the detected signals meeting the threshold, weighting the corresponding frequency and amplitude to obtain a frequency spectrum position, and taking the frequency spectrum position as the center f of the intercepted echorWherein A isnAnd fnRespectively, the amplitude and the spectral position corresponding to each point;
Figure BDA0001969371710000123
will be provided with
Figure BDA0001969371710000124
And
Figure BDA0001969371710000125
respectively as the central positions of the tracking wave gates of the positive frequency modulation and the negative frequency modulation;
the main-lobe cut 13 is based on the center position of the echo outputted from CFAR11, and cuts the echo with a specified width Wzx：
Figure BDA0001969371710000126
Wherein N is more than or equal to 0.5zp≤0.9；
According to the left side of the interception center during negative frequency modulation interception
Figure BDA0001969371710000127
Right side of the
Figure BDA0001969371710000128
Intercepting in proportion;
according to the left side of the interception center during positive frequency modulation interception
Figure BDA0001969371710000129
Right side of the
Figure BDA00019693717100001210
Intercepting in proportion;
and in the intercepted main lobe width, secondarily judging and intercepting the main lobe, wherein the judging conditions are as follows:
the amplitude of the signal in the main lobe exceeds a threshold, which is Nocog_n×Pn，2≤Nocog_nLess than or equal to 4; searching from the center of the wave gate to the left and right sides respectively if N is continuouslxIf the point signal amplitude does not exceed the threshold, the lower limit/upper limit of the main lobe is cut off, wherein N is more than or equal to 6lx≤20；
Center of gravity estimation value S:
Figure BDA0001969371710000131
wherein:
s[tr(m)]the main lobe signal processed by the FFT4 after the secondary interception is obtained;
and m is the FFT position point of the main lobe signal after the secondary interception.
The center of gravity of positive frequency modulation in the OCOG is used as
Figure BDA0001969371710000132
Negative frequency-modulated echo center as
Figure BDA0001969371710000133
Tracking distance RtThe calculation formula is as follows:
Figure BDA0001969371710000134
after the tracking is started, the effective tracking distance R of the periodtTrace recursion data R as next cycletrack。
In summary, according to the technical scheme of the embodiment of the present invention, a capture channel and a tracking channel are simultaneously processed, and first, the intermediate frequency signal is preprocessed, including AD sampling, demodulation filtering extraction, and FFT; the acquisition channel is then processed simultaneously with the tracking channel. Capturing channels comprises capturing CFAR and capturing echo center calculation, thereby obtaining a center position; and tracking the channel by using tracking wave gate interception, CFAR tracking, echo center tracking calculation, main lobe interception and OCOG (optical coherence tomography), so as to obtain the gravity center position of the echo main lobe and extract ranging information. The influence of the field value in the measuring process can be reduced by the cooperative processing of the capturing channel and the tracking channel, because the lander descends, the distance is within a certain dynamic range, the influence of the burr of the echo can be avoided by the tracking channel, and the tracking is stabilized within the tracking interception threshold. Even if a large dynamic condition exists, the distance measurement and speed measurement value can be timely calculated through the capture channel, and compared with the tracking channel, the tracking can be timely quit, and the central position of the tracking wave gate is determined again. Therefore, the target echo of the extraterrestrial celestial object surface can be effectively measured, hardware computing resources are reasonably distributed, and the processing speed and the ranging stability are improved.
The technical idea of the present invention and the embodiments according to the technical idea of the present invention are described above. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the examples given herein. This application is intended to cover any variations, uses, or adaptations of the invention. Such variations, uses, or adaptations are to be regarded as a general matter of the invention and include such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims. It will be understood that the invention is not limited to what has been described above and shown in the drawings, but that various modifications and changes can be made by those skilled in the art without departing from the scope of the present disclosure.

Claims (2)

1. A radar surface target echo signal ranging processing method for extraterrestrial celestial body landing measurement is characterized by comprising the following steps: the intermediate frequency echo (1) is preprocessed (5), processed by a ranging acquisition channel (8) and processed by a ranging tracking channel (16); wherein the content of the first and second substances,
preprocessing (5) the intermediate frequency echo (1), which comprises A/D sampling (2), demodulation filtering extraction (3) and FFT (4);
the range capture channel (8) processing comprises capturing a CFAR (6) and capturing an echo center calculation (7), thereby obtaining an echo main lobe center position (17); it includes:
the signal processed by the FFT (4) is detected by adopting a capture CFAR (6), and after a peak signal is detected, if the peak signal exceeds a detection threshold, an echo signal is judged to exist; wherein the detection threshold of the capture CFAR (6) is defined as NCFAR_n×Pn，4≤NCFAR_n≤10，PnNoise is calculated in a segmented mode on the signal amplitude processed by the FFT (4) for the noise amplitude, and after the noise is respectively calculated in an average mode, the noise statistical result with the minimum average value is used as the noise amplitude;
the center of the captured echo is calculated (7) by opening a window by taking the peak value of the signal after FFT (4) processing as the center, detecting the amplitude value exceeding the threshold, and calculating the center of the echo, and the operation is as follows:
the peak value of the detection window is taken as the center, and the left width and the right width are w1And w2Detecting whether the amplitude exceeds a threshold hsA point of (1), wherein w1＝wid×γ1，w2＝wid×γ2，wid＝fp×α, wherein 0.15- α -0.3, fpIs the frequency absolute value corresponding to the amplitude value exceeding the threshold, if the amplitude value is a positive slope echo, the frequency absolute value is
Figure FDA0002570392980000011
Figure FDA0002570392980000012
If it is a negative slope echo, then
Figure FDA0002570392980000013
Threshold hs＝Ap/Np，
Figure FDA0002570392980000014
Wherein A ispIs the amplitude of the peak;
extracting 10 signals with maximum amplitude from the detected signals meeting the threshold, weighting the corresponding frequency and amplitude to obtain a frequency spectrum position, and taking the frequency spectrum position as the center f of the intercepted echorWherein A isnAnd fnRespectively, the amplitude and the spectral position corresponding to each point;
Figure FDA0002570392980000015
formula 9;
will be provided with
Figure FDA0002570392980000016
And
Figure FDA0002570392980000017
as the gate centers (15) for positive and negative frequency modulation, respectively;
wherein the capture distance RcThe calculation formula is as follows:
Figure FDA00025703929800000211
wherein f issThe sampled signal sampling rate, c is the speed of light;
the ranging tracking channel (16) processing includes tracking gate intercept (10), tracking CFAR (11), tracking echo center calculation (12), main lobe intercept (13) and OCOG (14) to derive a center of gravity position (18) to extract ranging information, which includes:
in the case of ranging, the tracking channel (16) is connected to a tracking channel enable (9), and if tracking has not been started, but the acquisition channel (8) has already acquired a valid acquisition distance,then tracking is initiated in the next cycle at the effective acquisition distance R of this cyclecTrace recursion data R as next cycletrack；
Tracking the recursion data R according to the distance of the previous periodtrackAnd velocity tracking recurrence data vtrackSetting the tracking wave gate center and width (15);
tracking wave gate center with negative frequency modulation
Figure FDA0002570392980000022
Figure FDA0002570392980000023
Wherein, λ is the carrier wavelength of speed measurement;
tracking wave gate center with positive frequency modulation
Figure FDA0002570392980000024
Figure FDA0002570392980000025
Tracking wave gate center WgzN of distance tracking recursion data with tracking gate width of last cyclebm0.15 or less of Nbm≤0.3：
Figure FDA0002570392980000026
According to the left side of the interception center during negative frequency modulation interception
Figure FDA0002570392980000027
Right side of the
Figure FDA0002570392980000028
Intercepting in proportion;
according to the left side of the interception center during positive frequency modulation interception
Figure FDA0002570392980000029
Right side of the
Figure FDA00025703929800000210
Intercepting in proportion;
adopting tracking CFAR (11) detection for the signals after FFT processing, and judging that echo signals exist if the peak signals exceed a detection threshold after the peak signals are detected; wherein the tracking CFAR (11) detection threshold is set as NCFAR_n×Pn；
The method comprises the following steps of (1) tracking the center of an echo, calculating (12) a window by taking a signal peak value processed by FFT (4) as a center, detecting an amplitude value exceeding a threshold, and calculating the center of the echo, wherein the operation is as follows:
the peak value of the detection window is taken as the center, and the left width and the right width are w1And w2Detecting whether the amplitude exceeds a threshold hsA point of (1), wherein w1＝wid×γ1，w2＝wid×γ2，wid＝fp×α, if it is a positive slope echo
Figure FDA0002570392980000031
If it is a negative slope echo, then
Figure FDA0002570392980000032
Extracting 10 signals with maximum amplitude from the detected signals meeting the threshold, weighting the corresponding frequency and amplitude to obtain a frequency spectrum position, and taking the frequency spectrum position as the center f of the intercepted echorWherein A isnAnd fnRespectively, the amplitude and the spectral position corresponding to each point;
Figure FDA0002570392980000033
will be provided with
Figure FDA0002570392980000034
And
Figure FDA0002570392980000035
respectively as the central positions of the tracking wave gates of the positive frequency modulation and the negative frequency modulation;
the main lobe interception (13) is based on tracking the center position of the echo outputted by the CFAR (11), and intercepts the echo with a specified width Wzx：
Figure FDA0002570392980000036
Wherein N is more than or equal to 0.5zp≤0.9；
According to the left side of the interception center during negative frequency modulation interception
Figure FDA0002570392980000037
Right side of the
Figure FDA0002570392980000038
Intercepting in proportion;
according to the left side of the interception center during positive frequency modulation interception
Figure FDA0002570392980000039
Right side of the
Figure FDA00025703929800000310
Intercepting in proportion;
and in the intercepted main lobe width, secondarily judging and intercepting the main lobe, wherein the judging conditions are as follows:
the amplitude of the signal in the main lobe exceeds a threshold, which is Nocog_n×Pn，2≤Nocog_nLess than or equal to 4; searching from the center of the wave gate to the left and right sides respectively if N is continuouslxIf the point signal amplitude does not exceed the threshold, the lower limit/upper limit of the main lobe is cut off, wherein N is more than or equal to 6lx≤20；
Center of gravity estimation value S:
Figure FDA0002570392980000041
wherein:
s[tr(m)]the main lobe signal after the FFT processing after the secondary interception is obtained;
m is an FFT position point of the main lobe signal after the secondary interception;
the center of gravity of the positive frequency modulation in the OCOG (14) is used as
Figure FDA0002570392980000042
Negative frequency-modulated echo center as
Figure FDA0002570392980000043
Tracking distance RtThe calculation formula is as follows:
Figure FDA0002570392980000044
after the tracking is started, the effective tracking distance R of the periodtTrace recursion data R as next cycletrack。
2. The method for processing the echo signal of the target of the extraterrestrial celestial body landing measurement radar surface as claimed in claim 1, wherein the preprocessing (5) of the intermediate frequency echo (1) comprises:
the radar received signal after A/D sampling (2) is formulated as:
Figure FDA0002570392980000045
wherein: t is time, TdFor delay of received signal relative to transmitted signal, Pr is received signal power, omega0Is the center angular frequency, f, of the linear frequency modulationdIs the frequency of the doppler frequency and is,
Figure FDA0002570392980000046
in order to transmit the initial phase of the signal,
Figure FDA0002570392980000047
for the initial phase of the received signal, NTzqIs the Nth frequency modulation period;
k is the frequency modulation slope,
Figure FDA0002570392980000048
for modulating bandwidth, TM5ms is a frequency modulation period;
and (3) performing decimation filtering on the radar receiving signal after the A/D sampling (2), and demodulating the data after the decimation filtering, wherein the demodulation formula is as follows:
Figure FDA0002570392980000051
wherein
Figure FDA0002570392980000052
In order to demodulate the signal for a positive frequency modulation,
Figure FDA0002570392980000053
is a positive frequency modulated received signal;
and (3) demodulating a real part signal:
Figure FDA0002570392980000054
demodulating the imaginary signal:
Figure FDA0002570392980000055
filtering the demodulated signal, the filtered signal:
Figure FDA0002570392980000056
negative frequency modulation demodulation of the filtered signal:
Figure FDA0002570392980000057
n is respectively carried out on positive frequency modulation echo signals and negative frequency modulation echo signalsFFTPoint FFT (4) processing
Figure FDA0002570392980000058
Figure FDA0002570392980000059
Figure FDA0002570392980000061
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