CN111175708B - Automatic gain control system and method for active phase scanning ground reconnaissance radar - Google Patents
Automatic gain control system and method for active phase scanning ground reconnaissance radar Download PDFInfo
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- CN111175708B CN111175708B CN201911312249.5A CN201911312249A CN111175708B CN 111175708 B CN111175708 B CN 111175708B CN 201911312249 A CN201911312249 A CN 201911312249A CN 111175708 B CN111175708 B CN 111175708B
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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
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/34—Gain of receiver varied automatically during pulse-recurrence period, e.g. anti-clutter gain control
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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
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/292—Extracting wanted echo-signals
- G01S7/2923—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods
- G01S7/2927—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods by deriving and controlling a threshold value
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
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Abstract
The invention discloses an automatic gain control system and a method of an active phase scanning ground reconnaissance radar, wherein the system comprises an array antenna, a T/R assembly, a frequency synthesis receiver, a wave control board, an electronic compass and a signal processing unit; the amplitude characteristics of fixed ground object echoes under different wave beam directions in the radar scanning range after being processed by intermediate frequency digitization, down-conversion extraction and filtration, pulse compression and the like are measured through presetting the gain of the receiver, and the gain control codes of the receiver under all directions are determined, so that an automatic gain control system for adaptively adjusting the gain of the receiver along with the environmental change of the ground object where the radar is positioned is realized. According to the invention, when the antenna beam points to different directions, the gain of the receiver can be adaptively adjusted according to the ground object echo power, so that the overflow distortion can not occur in the sampling of the strong ground object azimuth echo, the weak ground object azimuth echo is not attenuated, the quantization performance of the AD chip is fully utilized, the detection performance of the radar is improved, and the false alarm probability is reduced.
Description
Technical Field
The invention belongs to the field of digital signal processing of an active phase scanning ground reconnaissance radar, and particularly relates to an automatic gain control system and method of the active phase scanning ground reconnaissance radar.
Background
The active phased array technology has flexible and rapid beam pointing; multiple independent beams can be formed simultaneously, and comprehensive functions of target searching, tracking, identification, passive detection and the like are realized; the system has the advantages of high reliability, normal operation even if a small number of transmitting/receiving units fail, and the like, and can be widely applied to the field of ground activity target reconnaissance. The ground reconnaissance radar works in a strong ground clutter environment, a receiver is easily saturated by strong ground feature echoes, and the large dynamic range change of the ground feature echo intensity in the beam scanning process cannot be solved by the conventional time Sensitivity (STC) control technology of the pulse compression radar. Therefore, automatic gain control of the active phase scanning ground reconnaissance radar becomes an important factor affecting its performance.
In an active phase ground sweeping radar, a target echo is submerged by a strong ground object echo, when an antenna beam points to the direction of the strong ground object, a receiver can be saturated, signals entering an AD module of a signal processing board are distorted, interference and false alarms are generated, and the target detection performance is reduced. Currently, under the condition that the gain of a receiver is updated every scanning period, the conventional active phase ground sweeping radar is mostly fixed gain control or manual gain control, a fixed gain is built in software, whether the gain of the receiver needs to be adjusted or not is manually judged in the working process, but the amplitude of echoes of all directions cannot be made to be near the maximum unsaturated peak-to-peak value of the AD under the manual gain control, if the attenuation of the echoes is too small, the AD performance is not fully utilized, the radar detection performance is affected, and the target detection probability is reduced. When the ground object environment changes, the situation that the set gain is not matched with the current environment is necessarily generated, the user cannot accurately judge the current echo intensity, and the proper gain cannot be quantitatively determined.
Disclosure of Invention
The invention aims to provide an automatic gain control system and method for an active phase-scanning ground reconnaissance radar, which can automatically detect the current ground object echo power under different environments, dynamically adjust the gain of a receiver, fully utilize the quantization performance of an AD chip and improve the target detection performance.
The technical scheme for realizing the purpose of the invention is as follows: an automatic gain control system of an active phase scanning ground reconnaissance radar comprises an array antenna, a T/R assembly, a frequency synthesis receiver, a wave control board, an electronic compass and a signal processing unit;
the array antenna and the T/R component are used for receiving and transmitting radio frequency signals;
the wave control board is used for forwarding the wave control code and the channel gain code of the component;
the frequency synthesis receiver is used for outputting radio frequency emission signals and controlling the intermediate frequency output power of a receiving channel according to the channel gain code set by the wave control board;
the electronic compass is used for measuring radar erection azimuth;
the signal processing unit mainly comprises ADC, DAC, FPGA, DSP, a clock and a power supply; the ADC is used for digitizing the intermediate frequency receiving signals; the DAC is used for converting an intermediate frequency digital signal generated by the FPGA into an analog signal and outputting the analog signal; the DSP is used for acquiring erection azimuth parameters of the radar, controlling a working mode, setting the gain of a receiver, receiving pulse pressure data and calculating ground object echo power; the FPGA completes the generation of intermediate frequency transmitting signals, down conversion, extraction filtering, pulse compression and pulse pressure data transmission.
An automatic gain control method of an active phase scanning ground reconnaissance radar comprises the following steps:
the DSP switches the radar working mode into a ground object measuring mode, and presets a receiver gain control code;
the FPGA carries out quadrature down-conversion, extraction filtering, pulse compression and co-channel interference suppression processing on radar echoes;
the FPGA sends pulse pressure data of a plurality of repeated periods to the DSP through SRIO;
the DSP sums and averages the pulse pressure I, Q data in the effective receiving time area of a plurality of repeated periods according to the period to obtain I, Q data average value;
determining the maximum absolute value of the I, Q data average value, namely the maximum ground object intensity estimated value pointed by the current wave beam;
determining a receiver gain control code with the beam pointing downwards according to the maximum ground object intensity estimation;
the DSP stores different wave beam pointing receiver gain control codes, the gain control codes are forwarded to the receiver through the wave control board, and automatic gain control is completed after the FPGA is switched to a normal working mode.
Further, the radar working mode is divided into a normal working mode and a ground object measuring mode; the radar is in a normal detection target state in a normal working mode; the ground object measuring mode is used for measuring the intensity of the ground object pointed by different beams in the scanning range of-theta to +theta so as to determine the channel attenuation of the pulses 1, 2, … … and N pointed by different beams;
in the ground object measurement mode, the beam interval is delta theta, and a receiver gain control code G is preset 0 The pulse repetition period of the radar is T r The method is the same as the normal working mode, but does not perform coherent accumulation processing, and the combined pulse number in one coherent processing interval is M A CPI period is T CPI ＝T r ·M A The time required for completing one ground object measurement is as follows:
further, the DSP sums and averages the pulse pressure I, Q data in the effective receiving time area of multiple repetition periods according to the period, so as to obtain a I, Q data average value, which specifically includes:
in the ground object measurement mode, the emission time of pulse 1, pulse 2, pulse … and pulse N are respectively t 0 ～t 1 ,t 2 ～t 3 ,...,t 2N-2 ～t 2N-1 The receiving time is t respectively 1 ～t 2 ,t 3 ～t 4 ,...,t 2N-1 ～t 2N Wherein the emission time of pulse n is t 2n-2 ～t 2n-1 The receiving time is t 2n-1 ～t 2n ；
In a pulse repetition period T r The reception time of pulse n is:
Δt Rn ＝t 2n-1 -t 2n
let the sampling frequency of the intermediate frequency echo be f s Performing down-conversion, extraction and filtering, and pulse compression in FPGA, wherein the extraction multiple is D, and the data rate of pulse pressure after extraction is f s D; the number of samples after pulse n receives echo pulse pressure in one pulse repetition period is as follows:
will be M in one measurement period A I, Q data after processing pulse n echo of each pulse repetition period is transmitted to the DSP through SRIO, and the data are assumed to be respectivelyAndthe DSP performs pulse repetition period averaging on I, Q two paths of data, and the average result is that:
further, finding out the maximum absolute value of the average value of I, Q data to obtain the maximum ground object intensity estimated value:
further, the receiver gain control code with the beam pointing downwards is determined according to the maximum ground object intensity estimation, specifically:
assuming that the maximum pulse pressure maximum non-overflow threshold after processing the maximum unsaturated echo is A 0 The gain to be increased by the receiver is
The radar should set the receiver gain control code to pulse n in this direction
Compared with the prior art, the invention has the remarkable advantages that: according to the invention, when the antenna beam points to different directions, the gain of the receiver can be adaptively adjusted according to the ground object echo power, so that the overflow distortion can not occur in the sampling of the strong ground object azimuth echo, the weak ground object azimuth echo is not attenuated, the quantization performance of the AD chip is fully utilized, the detection performance of the radar is improved, and the false alarm probability is reduced.
The invention is described in further detail below with reference to the accompanying drawings.
Drawings
Fig. 1 is a schematic diagram of a chirped pulse combined signal.
Fig. 2 is a block diagram of an automatic gain control system.
Fig. 3 is an automatic gain control flow chart of an example of the present invention.
Fig. 4 is a schematic diagram of pulse pressure peaks under manual gain control with beam pointing-10 deg..
Fig. 5 is a schematic diagram of pulse pressure peaks under automatic gain control with beam pointing-10 deg..
Detailed Description
The invention provides an automatic gain control system of an active phase scanning ground reconnaissance radar, which comprises an array antenna, a T/R assembly, a frequency synthesis receiver, a wave control board, an electronic compass and a signal processing unit, wherein the T/R assembly is connected with the array antenna;
the array antenna and the T/R assembly complete the receiving and transmitting of radio frequency signals;
the wave control board is used for forwarding the wave control code and the channel gain code of the component, and all control data come from the signal processing unit;
the frequency synthesis receiver is used for outputting radio frequency emission signals and controlling the intermediate frequency output power of the receiving channel according to the channel gain code set by the wave control board;
the electronic compass is used for measuring radar erection azimuth;
the signal processing unit mainly comprises a high speed ADC, DAC, FPGA, DSP, a clock and a power supply; the high-speed ADC mainly realizes the digitization of intermediate frequency receiving signals; the high-speed DAC converts an intermediate frequency digital signal generated by the FPGA into an analog signal and outputs the analog signal; the DSP realizes the acquisition of erection azimuth parameters of the radar, the control of a working mode, the setting of the gain of a receiver, the receiving of pulse pressure data and the calculation of ground object echo power; the FPGA completes the generation of intermediate frequency transmitting signals, down conversion, extraction filtering, pulse compression and pulse pressure data transmission.
The invention also provides an automatic gain control method of the active phase scanning ground reconnaissance radar, which is characterized in that a ground object measurement mode is set, an automatic gain control system is established under the mode, and the echo intensities of different distance segments of the areas of the pulse 1 to the pulse N corresponding to each azimuth are respectively measured by considering the combination waveforms of the linear frequency modulation pulses of the pulse 1, the pulse 2, the pulse … and the pulse N of the radar emission waveform;
when the radar working environment changes, the DSP switches the working mode into a ground object measuring mode, a larger receiver attenuation amount is preset, so that ground object echoes in all directions are ensured not to overflow and distort, the beam pointing is controlled to scan all directions in sequence, and each direction scans M A Pulse repetition Period (PRI). Sending the pulse 1-pulse N intermediate frequency echo signals digitized by the ADC into an FPGA for processing, sending the data processed by quadrature down-conversion, extraction, clutter suppression, common-frequency asynchronous interference suppression, pulse compression and sidelobe suppression into a DSP through an SRIO high-speed interface, and analyzing the echo intensity by the DSP to determine the receiver gain control codes of each azimuth and each pulse; in the normal working mode, the signal processing unit sets the receiver gain control codes corresponding to the wave beam pointing pulses 1-N to realize automatic gain control.
The following describes the present invention in detail.
The automatic gain control method of the active phase sweeping ground radar comprises the steps of presetting the gain of a receiver, measuring amplitude characteristics of fixed ground object echoes under different beam directions in a radar scanning range after being processed by intermediate frequency digitization, down-conversion extraction and filtration, pulse compression and the like, and determining the gain control code of the receiver in each direction, so that the automatic gain control for adaptively adjusting the gain of the receiver along with the environmental change of the ground object where the radar is positioned is realized.
Active phase swept radar waveform employing time width (τ) 1 ,τ 2 ,...,τ N ) A composite pulse waveform combining different chirped pulse signals (pulse 1, pulse 2, … …, pulse N) of the same bandwidth B. The radar operation mode is divided into a normal operation mode and a ground object measurement mode. The radar is in normal detection purpose in normal working modeAnd (5) marking. The ground object measuring mode is used for measuring the intensity of the ground object pointed by different beams in the scanning range of-theta to +theta, so that the channel attenuation of the pulses 1, 2, … … and N pointed by different beams is determined, and the radar receiving system is ensured to be in an optimal working state by the automatic gain control method in any terrain environment.
Before the radar is started to enter a normal working mode, a signal processing unit controls a radar host to finish ground object measurement, and channel attenuation amounts of pulse 1, pulse 2, pulse … … and pulse N in a scanning range of-theta to +theta are determined and stored; in operation, if the radar erection direction changes by more than theta 0 And when the signal processing unit performs ground object automatic measurement again, determining the channel attenuation of each beam pointing pulse 1-pulse N in the new beam scanning range.
In the ground object measurement mode, the beam interval is delta theta, and a larger receiver gain control code G is preset 0 (dB), the pulse repetition period of the radar is T r The same as the normal operation mode, but without the coherent accumulation process, the combined pulse number in one Coherent Processing Interval (CPI) is M A CPI period is T CPI ＝T r ·M A The time required for completing one-time ground object measurement is
The FPGA transmits I, Q pulse compression results of the pulse 1, the pulse 2, the pulse … and the pulse N to the DSP through SRIO, and the DSP calculates the channel attenuation amounts of the pulse 1, the pulse 2, the pulse … and the pulse N in different directions according to pulse pressure data and stores the channel attenuation amounts as the channel attenuation values in the directions in a follow-up normal working mode.
In the ground object measurement mode, the emission time of pulse 1, pulse 2, pulse … and pulse N are respectively t 0 ～t 1 ,t 2 ～t 3 ,...,t 2N-2 ～t 2N-1 The receiving time is t respectively 1 ～t 2 ,t 3 ～t 4 ,...,t 2N-1 ～t 2N Wherein the emission time of pulse n is t 2n-2 ～t 2n-1 The receiving time is t 2n-1 ～t 2n As shown in fig. 1. The process flow of the automatic gain control system will be described below by taking pulse n as an example.
In a pulse repetition period T r In, the pulse n is received for a time of
Δt Rn ＝t 2n-1 -t 2n
Let the sampling frequency of the intermediate frequency echo be f s (MSPS) performing down-conversion, extraction and filtering, and pulse compression in FPGA, wherein the extraction multiple is D, and the data rate of pulse pressure after extraction is f s /D (MSPS). The number of samples after pulse n receives echo pulse pressure in one pulse repetition period is
The data after down-conversion, extraction filtering, pulse pressure and other treatments are divided into I, Q two paths of data, M is measured in one measuring period A I, Q data after processing pulse n echo of each pulse repetition period is transmitted to the DSP through SRIO, and the data are assumed to be respectivelyAnd->The DSP performs pulse repetition period averaging on I, Q paths of data, and the result after the averaging is that
Searching the maximum absolute value in the averaged data to obtain the maximum ground object intensity estimated value
Assuming that the maximum pulse pressure maximum non-overflow threshold after processing the maximum unsaturated echo is A 0 The gain to be increased by the receiver is
The radar should set the receiver gain control code to pulse n in this direction
And sequentially calculating gain control codes of pulse 1, pulse 2, pulse … … and pulse N in a scanning range of-theta to +theta, storing the results into a buffer area of the DSP, setting a wave control board in a normal working mode, and controlling the gain control codes of each wave beam of the frequency synthesis receiver to be directed downwards. When the radar is started or the azimuth center indicated by the electronic compass changes in the working process, the signal processing unit controls the radar system to work in a ground object measuring mode, the ground object intensity in the range of-theta to +theta is measured again, the channel attenuation of each pulse in different scanning azimuth is determined, automatic gain control is realized, and the system block diagram is shown in figure 2.
The present invention will be described in detail with reference to examples and drawings.
Examples
And estimating the ground object intensity and calculating and storing an automatic gain control code in a ground object measurement mode. Let the transmitting signal be 2 pulse combined waveform, the time width of the signal be t respectively T1 ＝0.5us，t T2 =20us, the reception times are t respectively R1 ＝29.5us，t R2 =100 us, from which the effective reception times are taken to be t 'respectively' R1 ＝16.67us，t' R2 83.33us, signal bandwidth b=30 MHz, pulse repetition period number M A Sample frequency f of intermediate frequency echo =100 s =80 MHz, the extraction multiple d=8/3, the data rate after extraction is 30MSPS, the number of I, Q two paths after pulse 1 and pulse 2 is N 1 =500 and N 2 =2500. After pulse pressure treatmentThe data are transmitted to the DSP through SRIO to estimate the ground object intensity, and the gain control code of the receiver is calculated. With reference to fig. 3, the automatic gain control system is implemented as follows:
1) Transmitting a message to a wave control board, setting the pointed beam direction, and presetting a receiver gain control code to be 20dB from-45 degrees to +45 degrees at an interval of 0.5 degrees;
2) Setting an FPGA working mode as a ground object measurement mode;
3) Receiving pulse pressure data of 100 repeated cycles through SRIO;
4) The pulse pressure I, Q data of the 100 repetition periods are respectively summed and averaged to obtain I, Q average values of the effective receiving time areas of the pulse 1 and the pulse 2Is->
5) Finding out the maximum absolute value of all I, Q data after the average of pulse 1 and pulse 2, namely the ground object intensity estimated value of the current beam direction
6) Determining the receiver gain control code for the downward pointing beam based on the feature intensity estimates for pulse 1 and pulse 2, respectivelyWherein A is 0 =27000 is the maximum unsaturation value;
7) The DSP stores different beam pointing receiver gain control codes.
Under the condition that the radar azimuth does not change, the radar works in a normal working mode, the DSP sets the gain of the receiver according to the current beam direction, when the radar erection azimuth changes by more than 3 degrees, the terminal sends an automatic ground feature measurement command to the host, the signal processing unit carries out automatic ground feature measurement again, and the normal working mode is continued after the completion.
The radar azimuth scanning range is set to be-10 degrees to 10 degrees, namely the beam pointing is changed from-10 degrees to 10 degrees at equal intervals, the manual setting gain ensures that AD sampling data is unsaturated in the scanning range, the maximum absolute value of I, Q paths of pulse pressure after pulse 2 is recorded is averaged, and the pulse pressure peak value under the manual gain control of the beam pointing of-10 degrees to 10 degrees is obtained as shown in figure 4. The azimuth scanning range is kept unchanged, the automatic gain control system in the invention is used for setting gain, the maximum absolute value of the pulse pressure of pulse 2 after I, Q is recorded, and the pulse pressure peak value under the automatic gain control of the wave beam direction of-10 degrees to 10 degrees is obtained as shown in figure 5. As shown in fig. 4 and fig. 5, when the gain is manually set, it is only ensured that no overflow point exists in the scanning range from-10 ° to 10 °, but pulse pressure peak values in different directions change from 2000 to 21000, too small pulse pressure peak values mean that the quantization performance of the AD cannot be well applied, and the performance loss is very large, and after the automatic gain control system is used, it is ensured that the pulse pressure peak values in the scanning range are slightly smaller than the maximum non-overflow threshold, and the quantization performance of the AD can be fully utilized.
Claims (5)
1. The automatic gain control method of the active phase scanning ground reconnaissance radar is characterized in that the control method is realized based on an automatic gain control system, and the automatic gain control system comprises an array antenna, a T/R assembly, a frequency synthesis receiver, a wave control board, an electronic compass and a signal processing unit;
the array antenna and the T/R component are used for receiving and transmitting radio frequency signals;
the wave control board is used for forwarding the wave control code and the channel gain code of the component;
the frequency synthesis receiver is used for outputting radio frequency emission signals and controlling the intermediate frequency output power of a receiving channel according to the channel gain code set by the wave control board;
the electronic compass is used for measuring radar erection azimuth;
the signal processing unit mainly comprises ADC, DAC, FPGA, DSP, a clock and a power supply; the ADC is used for digitizing the intermediate frequency receiving signals; the DAC is used for converting an intermediate frequency digital signal generated by the FPGA into an analog signal and outputting the analog signal; the DSP is used for acquiring erection azimuth parameters of the radar, controlling a working mode, setting the gain of a receiver, receiving pulse pressure data and calculating ground object echo power; the FPGA completes the generation of intermediate frequency transmitting signals, down-conversion, extraction filtering, pulse compression and pulse pressure data transmission;
the control method comprises the following steps:
the DSP switches the radar working mode into a ground object measuring mode, and presets a receiver gain control code;
the FPGA carries out quadrature down-conversion, extraction filtering, pulse compression and co-channel interference suppression processing on radar echoes;
the FPGA sends pulse pressure data of a plurality of repeated periods to the DSP through SRIO;
the DSP sums and averages the pulse pressure I, Q data in the effective receiving time area of a plurality of repeated periods according to the period to obtain I, Q data average value;
determining the maximum absolute value of the I, Q data average value, namely the maximum ground object intensity estimated value pointed by the current wave beam;
determining a receiver gain control code with the beam pointing downwards according to the maximum ground object intensity estimation;
the DSP stores different wave beam pointing receiver gain control codes, the gain control codes are forwarded to the receiver through the wave control board, and automatic gain control is completed after the FPGA is switched to a normal working mode.
2. The automatic gain control method of an active phase scanning ground reconnaissance radar according to claim 1, wherein the radar operation mode is divided into a normal operation mode and a ground object measurement mode; the radar is in a normal detection target state in a normal working mode; the ground object measuring mode is used for measuring the intensity of the ground object pointed by different beams in the scanning range of-theta to +theta so as to determine the channel attenuation of the pulses 1, 2, … … and N pointed by different beams;
wave in ground object measuring modeThe beam interval is delta theta, and a receiver gain control code G is preset 0 The pulse repetition period of the radar is T r The number of combined pulses in one coherent processing interval is M A CPI period is T CPI ＝T r ·M A The time required for completing one ground object measurement is as follows:
3. the automatic gain control method of an active phase scanning ground reconnaissance radar according to claim 2, wherein the DSP sums and averages pulse pressure I, Q data in a plurality of repetition period effective receiving time areas according to periods to obtain I, Q data average values, specifically:
in the ground object measurement mode, the emission time of pulse 1, pulse 2, pulse … and pulse N are respectively t 0 ～t 1 ,t 2 ～t 3 ,...,t 2N-2 ～t 2N-1 The receiving time is t respectively 1 ～t 2 ,t 3 ～t 4 ,...,t 2N-1 ～t 2N Wherein the emission time of pulse n is t 2n-2 ～t 2n-1 The receiving time is t 2n-1 ～t 2n ；
In a pulse repetition period T r The reception time of pulse n is:
Δt Rn ＝t 2n-1 -t 2n
let the sampling frequency of the intermediate frequency echo be f s Performing down-conversion, extraction and filtering, and pulse compression in FPGA, wherein the extraction multiple is D, and the data rate of pulse pressure after extraction is f s D; the number of samples after pulse n receives echo pulse pressure in one pulse repetition period is as follows:
will be M in one measurement period A I, Q data after processing pulse n echo of each pulse repetition period is transmitted to the DSP through SRIO, and the data are assumed to be respectivelyAndthe DSP performs pulse repetition period averaging on I, Q two paths of data, and the average result is that:
4. the automatic gain control method of an active phase scanning ground reconnaissance radar according to claim 3, wherein a maximum absolute value of a I, Q data average value is found to obtain a maximum ground object intensity estimated value:
5. the automatic gain control method of an active phase scanning ground reconnaissance radar of claim 4, wherein determining the receiver gain control code with the beam pointing downward based on the maximum ground object intensity estimate comprises:
assuming that the maximum pulse pressure maximum non-overflow threshold after processing the maximum unsaturated echo is A 0 The gain to be increased by the receiver is
The radar should set the receiver gain control code to pulse n in this direction
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| CN108594197B (en) * | 2018-06-27 | 2022-03-04 | 南京理工大学 | Ground radar self-adaptive distance amplitude weighting system and method |
| CN109298403B (en) * | 2018-11-29 | 2023-10-20 | 中国电子科技集团公司第二十七研究所 | High-speed signal processing and beam control device and method |
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