CN109444838B - Method and system for solving velocity ambiguity based on pulse accumulation frame dual frequency - Google Patents
Method and system for solving velocity ambiguity based on pulse accumulation frame dual frequency Download PDFInfo
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Abstract
The invention discloses a method and a system for resolving speed ambiguity based on pulse accumulation frame dual frequency, comprising the following steps: the transmitting subsystem is characterized in that a baseband signal generating module generates a Barker code or a linear frequency modulation signal and outputs the Barker code or the linear frequency modulation signal to a microwave transmitting module to mix the received baseband signal, modulate the baseband signal to a microwave frequency band, amplify the power and output the baseband signal to an external antenna to radiate the space; the receiving subsystem, wherein the microwave receiving module down-converts the echo signal input by the receiving antenna from the microwave frequency band to the intermediate frequency, and outputs the echo signal to the intermediate frequency receiving module for intermediate frequency signal gain control, and controls the amplitude level of the intermediate frequency signal output to the signal processing module within a proper range, the signal processing module adjusts the pulse repetition frequency between frames according to the type of the pulse accumulation frame, alternately completes the accumulation of the high repetition frequency speed measurement frame and the accumulation of the low repetition frequency distance measurement frame, generates corresponding synchronous pulses and outputs the synchronous pulses to other modules, and simultaneously completes the functions of signal acquisition, pulse compression accumulation and target detection.
Description
Technical Field
The invention relates to the technical field of radar, in particular to a method and a system for resolving speed ambiguity based on pulse accumulation frame dual frequency.
Background
The space-based tracking and aiming radar mainly detects and measures a space non-cooperative target, and for a high-speed moving target, the ultra-long-range tracking and aiming radar has the problem of fuzzy contradiction of distance and speed measurement. The existing speed ambiguity resolution mainly adopts a DSP software processing method, and when a radar is interfered or the detection signal-to-noise ratio is low, the order of the speed ambiguity is difficult to judge.
In the prior patent, "TPRF method for doppler weather radar to resolve velocity ambiguity" (application number: 201010270482.4), a multi-pulse repetition frequency detection technique is disclosed, in which three suitable pulse repetition frequencies are selected to form two DPRF detections, and the actual velocity is calculated according to the measurement result. A method for solving range-speed ambiguity based on changing signal modulation frequency (grant No. 201410353579.X) designs N pulse signals by selecting different signal time widths, a radar transmits the pulse signals according to a time sequence and receives echo signals of the pulse signals, a designed matched filter is used for carrying out matched filtering on the echo signals and judging whether effective pulse pressure is achieved or not, range ambiguity times are obtained, and range ambiguity-free distance and ambiguity-free speed are calculated. The 'speed ambiguity resolving algorithm based on the fast lookup table method' (application number: 201610600630.1) uses four different repetition frequencies and a pre-established speed ambiguity resolving table to resolve the actual speed row by column in a circular algorithm. An intra-pulse dual-frequency speed-reducing fuzzy and distance fuzzy method and system (application number: 201710379519.9) generates two paths of transmitting excitation signals with different frequencies, and the receiving process uses the frequency difference of the two frequencies of echo signals to calculate the time speed. The four schemes are all to indirectly obtain the actual speed according to the proportional relation of the measurement result by utilizing multiple complex frequencies, different emission pulse waveforms or different emission frequencies.
In the article, the LFMCW radar high-speed target speed ambiguity resolution new method is a track association ambiguity resolution method, and the target average speed is calculated by modeling the target motion, and the maximum ambiguity-free speed coefficient is estimated by using the average speed. A new SAR-GMTI speed ambiguity resolving method is provided in a new method for resolving the ambiguity of the radial speed of a moving target, and meanwhile, the ambiguity resolving capability of an offset baseline and an offset frequency is utilized. A method for resolving the fuzzy of PD system frequency agility radar uses a distance fuzzy table established in advance to resolve the distance fuzzy, and then resolves the actual speed according to multiple PRFs. The documents and the retrieved patents adopt a software method to indirectly solve the fuzzy speed.
Disclosure of Invention
The invention provides a method and a system for resolving velocity ambiguity based on pulse accumulation frame double frequency, which alternately realize unambiguous distance measurement and unambiguous velocity measurement by changing the double frequency between pulse accumulation frame frames, directly detect and obtain a target velocity measurement value, and have the advantage of high velocity measurement precision under the condition of low signal-to-noise ratio.
The method can solve the problem of fuzzy contradiction of ultra-long distance detection distance and speed, is applied to the fields of space-based non-cooperative target tracking measurement and the like such as satellites, space stations and the like, and can directly obtain the measurement information such as the distance, the speed and the like of the target.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
a dual-frequency velocity ambiguity resolution system based on pulse accumulation frames, comprising: the device comprises a circulator, an antenna, a transmitting subsystem and a receiving subsystem; the transmitting subsystem also comprises a baseband signal generating module and a microwave transmitting module; the receiving subsystem also comprises a microwave receiving module, an intermediate frequency receiving module and a signal processing module; the transmitting subsystem and the receiving subsystem are respectively connected with the antenna through the circulator; the microwave transmitting module, the baseband signal generating module, the microwave receiving module and the intermediate frequency receiving module receive the synchronous pulse signals output by the signal processing module and carry out receiving and transmitting time sequence synchronization. The baseband signal generating module generates a Barker code or a linear frequency modulation baseband signal and outputs the Barker code or the linear frequency modulation baseband signal to the microwave transmitting module; the microwave transmitting module is used for mixing the received baseband signals, modulating the baseband signals to a microwave frequency band, amplifying the power of the microwave frequency band and outputting the microwave frequency band to the circulator; the microwave receiving module down-converts the received echo signal from a microwave frequency band to an intermediate frequency and outputs the signal to the intermediate frequency receiving module; the intermediate frequency receiving module performs intermediate frequency signal gain control, controls the amplitude level of an intermediate frequency signal output to the signal processing module within a proper range, and the signal processing module adjusts the pulse repetition frequency between frames according to the type of a pulse accumulation frame, alternately completes high-repetition-frequency speed measurement frame accumulation and low-repetition-frequency distance measurement frame accumulation, generates a corresponding synchronous pulse signal and outputs the synchronous pulse signal to other modules, and simultaneously completes the functions of signal acquisition, pulse compression accumulation and target detection.
Preferably, the signal processing module comprises an a/D sampling unit, a digital down-conversion unit, a pulse compression unit, a pulse accumulation unit, an inter-frame switching control unit and a target detection unit. The A/D sampling unit performs band-pass digital-to-analog conversion on the intermediate frequency signal and then caches data in an FIFO; the digital down-conversion unit digitally mixes the intermediate frequency signal to a baseband, performs low-pass filtering, and performs extraction according to the signal bandwidth; the pulse compression unit performs pulse compression on the Barker code or the linear frequency modulation signal, so that the distance resolution is improved; the pulse accumulation unit ping-pong stores the data after pulse pressure into two external SRAMs; the target detection unit ping-pong reads the two-dimensional plane data after pulse pressure from the SRAM; the inter-frame switching control unit is a working state main controller of the whole signal processor, adjusts pulse repetition frequency between frames according to the type of a pulse accumulation frame, and alternately completes high-repetition-frequency speed measurement frame accumulation and low-repetition-frequency distance measurement frame accumulation; the digital down-conversion unit, the pulse compression unit, the pulse accumulation unit and the inter-frame switching control unit are realized on an FPGA chip; the target detection unit is implemented in a DSP chip.
Preferably, the signal processing module further includes the repetition frequency adjusting unit, which completes the detection of the ranging frame target at the DSP, obtains target unambiguous distance information, determines whether the target falls within the velocity measurement frame emission blind area, and if the target falls within the emission blind area, finely adjusts the velocity measurement frame repetition frequency period to prevent the target from being folded back into the emission blind area.
Preferably, the repetition frequency of the ranging frame pulse is F, the time width of the transmitted signal is T1, the time width of the range gate is T2, the number of accumulated pulses is M, the repetition frequency of the ranging frame pulse is F × N, the time width of the transmitted signal is T1/N, the time width of the range gate is T2/N, the number of accumulated pulses is M × N, and the fuzzy order N is a 2-power relationship.
Preferably, the distance of the unambiguous remote target obtained by measuring the distance measurement frame is R, the target distance can be reflected for multiple times in the velocity measurement frame, and the target distance R is modulo according to C/2/(F × N) at the position R' of the velocity measurement frame. If the result of dividing the modulus value by (C/2) is smaller than the time width T1/N of the transmitted signal, C is the speed of light, the repetition period of the tachometer frame is finely adjusted, the product of the adjustment quantity and K is larger than the time width of the transmitted signal, K is floor (R/(C/2/(F) N)), and floor is a downward integer operator.
In the method and the system for resolving the speed ambiguity based on the pulse accumulation frame dual frequency, the working state of the interframe switching control module comprises the following steps:
a1, the interframe switching control unit controls the radar to work in a ranging frame work mode through a synchronous pulse, signal transmission and echo reception are completed in each repetition frequency period, data are written into an SRAM1 after pulse compression, and the current repetition frequency echo data are processed and then jump to A2;
a2, judging whether the pulse accumulation unit finishes the accumulation of M effective pulses, if so, jumping to the step A3, and if not, jumping to the step A1 to continue the execution;
a3, setting a next frame type mark 0x55, updating a speed measurement frame repetition frequency period, and jumping to the step A4;
a4, the interframe switching control unit controls the radar to work in a speed measurement frame working mode through a synchronous pulse, signal transmission and echo reception are completed in each repetition frequency period, data are written into an SRAM2 after pulse compression, and the current repetition frequency echo data are processed and then jump to A5;
a5, judging whether the pulse accumulation unit finishes the accumulation of M-N effective pulses, if so, jumping to the step A3, and if not, jumping to the step A4 to continue the execution;
a6, setting the next frame type flag to 0xAA, and jumping to step A1.
In the method and system for resolving the speed ambiguity based on the double frequency of the pulse accumulation frame, the working state of the double frequency adjusting unit comprises the following steps:
b1, waiting for finishing the accumulation of the ranging frame pulse, and jumping to the step B2 when the frame type mark is changed from 0xAA to 0x 55;
b2, reading ranging frame data, performing coherent accumulation and target detection to obtain unambiguous distance information, and jumping to the step B3;
b3, judging whether the repetition frequency period of the speed measurement frame is finely adjusted, if so, jumping to the step B4, and if not, jumping to the step B7;
b4, keeping the repetition frequency period of the speed measurement frame unchanged;
b5, judging whether the target is reversely folded and falls in a high repetition frequency emission blind area according to the target unambiguous distance calculated in the step B2 and the finely adjusted repetition frequency period of the speed measurement frame, if so, jumping to the step B6, and if not, jumping to the step B10;
b6, the speed measurement frame is recovered to the speed measurement frame repetition frequency period before adjustment, and the step B10 is skipped;
b7, reducing the repetition frequency period of the tachograph frame to 1/(F N), reducing the time width of the emission signal to T1/N, reducing the range gate to T2/N, and jumping to the step B8;
b8, judging whether the target is reversely folded and falls in a high repetition frequency emission blind area according to the target unambiguous distance calculated in the step B2 and the finely adjusted repetition frequency period of the speed measurement frame, if so, jumping to the step B9, and if not, jumping to the step B10;
b9, calculating according to the target unambiguous distance R and the velocity measurement frame repetition frequency period obtained in the step B2 to obtain a velocity measurement frame repetition frequency period without emission blind area shielding, and jumping to the step B10 after calculation is finished;
b10, completing the repetition frequency period configuration of the speed measurement frame, and jumping to the step B11;
b11, finishing the ranging frame processing.
Compared with the prior art, the invention has the following advantages:
in a monopulse tracking radar, the low repetition frequency increases the target unambiguous detection distance, but is easy to generate speed ambiguity; the high repetition frequency improves the target unambiguous velocity measurement range, but easily generates distance ambiguity, and the velocity ambiguity problem during remote detection can be solved by adopting a double-frequency velocity ambiguity resolution method based on pulse accumulation frames.
The scheme of the prior art usually utilizes multiple complex frequencies, different emission pulse waveforms or different emission frequencies to indirectly obtain the actual speed according to the proportional relation of measurement results, but the invention alternately completes low repetition frequency pulse accumulation and high repetition frequency pulse accumulation by changing the repetition frequency of a pulse accumulation frame, and directly calculates to obtain the unambiguous distance and the unambiguous speed.
The invention solves the problem of fuzzy distance and speed contradiction during ultra-long distance detection of the tracking radar, and has the advantages of high speed measurement precision and strong anti-interference capability. According to the invention, the alternate processing of the FPGA ranging pulse accumulation frame and the speed measurement pulse accumulation frame is realized by utilizing the interframe switching control unit, the DSP obtains the non-fuzzy distance information according to the ranging frame, calculates the repetition frequency period of the speed measurement frame, and finally directly detects the target according to the speed measurement frame to obtain the non-fuzzy speed measurement information.
Drawings
FIG. 1 is a block diagram of the basic components of a dual-frequency velocity ambiguity resolution system based on pulse accumulation frames according to the present invention;
FIG. 2 is a block diagram of a signal processing module in a dual-frequency velocity ambiguity resolution system based on pulse accumulation frames according to the present invention;
FIG. 3 is a timing diagram of the synchronization pulses and the transmitted signals during normal operation of the present invention;
FIG. 4 is a flow chart of the working state of the inter-frame switching control module in the pulse accumulation frame based dual-frequency velocity ambiguity resolution system according to the present invention;
FIG. 5 is a flow chart of the operation status of the repetition rate adjustment unit in the dual-frequency velocity ambiguity resolution system based on pulse accumulation frames according to the present invention.
Detailed Description
The present invention will now be further described by way of the following detailed description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings.
As shown in fig. 1, the present invention provides a dual-frequency velocity ambiguity resolution system based on pulse accumulation frame, comprising: circulator, antenna, transmitting subsystem for up-conversion and power amplification of baseband signal, and receiving subsystem for receiving and processing echo signal.
The transmitting subsystem also comprises a baseband signal generating module and a microwave transmitting module; the receiving subsystem also comprises a microwave receiving module, an intermediate frequency receiving module and a signal processing module.
The microwave transmitting module, the baseband signal generating module, the microwave receiving module and the intermediate frequency receiving module receive the synchronous pulse signals output by the signal processing module and carry out receiving and transmitting time sequence synchronization.
The baseband signal generating module generates a Barker code or linear frequency modulation baseband signal, the frequency of the signal is 70MHz, the bandwidth of the signal is 2MHz, and the signal is output to the microwave transmitting module.
And the microwave transmitting module is used for mixing the received baseband signals, modulating the baseband signals to a microwave Ka frequency band, amplifying the power of the baseband signals and outputting the microwave Ka frequency band to the circulator.
The microwave receiving module down-converts the received echo signal from the microwave Ka frequency band to the intermediate frequency of 70MHz, and outputs the signal to the intermediate frequency receiving module.
The intermediate frequency receiving module performs intermediate frequency signal gain control, controls the amplitude level of the intermediate frequency signal output to the signal processing module within a proper range, and controls the output level at 1/2 of full-scale input voltage of the A/D analog-to-digital conversion chip.
The signal processing module adjusts the pulse repetition frequency between frames according to the type of the pulse accumulation frame, alternately completes the accumulation of a speed measurement frame with high repetition frequency and the accumulation of a distance measurement frame with low repetition frequency, generates corresponding synchronous pulses and outputs the synchronous pulses to other modules, and simultaneously completes the functions of signal acquisition, pulse compression accumulation and target detection.
As shown in fig. 2, in this embodiment, the signal processing module includes an a/D sampling unit, a digital down-conversion unit, a pulse compression unit, a pulse accumulation unit, an inter-frame switching control unit, a target detection unit, and an emphasis adjustment unit.
The digital down-conversion unit, the pulse compression unit, the pulse accumulation unit and the inter-frame switching control unit are realized on an FPGA chip; the target detection unit and the repetition frequency adjustment unit are realized in a DSP chip.
The A/D sampling unit performs band-pass digital-to-analog conversion on the intermediate frequency signal, a 14-bit high-speed analog-to-digital conversion core is adopted for improving the signal-to-noise ratio, the sampling rate is 40M, a band-pass sampling processing mode is adopted, and then data are cached in an FIFO.
The digital down-conversion unit digitally mixes the intermediate frequency signal to a baseband and performs low-pass filtering, the passband cut-off frequency is 2MHz, the stopband cut-off frequency is 2.5MHz, and 1/20 extraction is performed according to the signal bandwidth.
The pulse compression unit performs pulse compression on the Barker code or the linear frequency modulation signal to improve the distance resolution.
The pulse accumulation unit stores data after pulse pressure into two external SRAMs in a ping-pong manner, a ranging frame adopts a low repetition frequency mode, pulse pressure data are written into the SRAMs 1, 256 pulses are accumulated to finish ranging frame processing, a frame completion flag is set to be 0xAA, a speed measurement frame adopts a high repetition frequency mode, pulse pressure data are written into the SRAMs 2, 4096 pulses are accumulated to finish speed measurement frame processing, and a frame completion flag is set to be 0x 55.
The target detection unit ping-pong reads the two-dimensional plane data after pulse pressure from the SRAM, the change of the state of the frame mark indicates that the FPGA completes one frame data processing, when the frame mark is changed from 0xAA to 0x55, the DSP can read the ranging frame data, and when the frame mark is changed from 0x55 to 0xAA, the DSP can read the speed measurement frame data.
The interframe switching control unit is a main controller of the working state of the whole signal processor, adjusts the pulse repetition frequency between frames according to the type of the pulse accumulation frame, and alternately completes the accumulation of the speed measurement frame with high repetition frequency and the accumulation of the distance measurement frame with low repetition frequency.
The repetition frequency adjusting unit is used for finishing the detection of the ranging frame target at the DSP, obtaining the target non-fuzzy distance information, judging whether the target falls in the speed measuring frame emission blind area or not, and finely adjusting the repetition frequency period of the speed measuring frame if the target falls in the emission blind area, so as to prevent the target from being folded back into the emission blind area.
As shown in fig. 3, the tachometer frame is triggered by the high repetition frequency synchronization pulse to transmit and receive the timing sequence, the effective pulse accumulation number is 4096, the pulse transmission time width is 16us, and the repetition frequency period is 125 us; the ranging frame is triggered by a low-repetition-frequency synchronous pulse to transmit and receive a time sequence, the effective pulse accumulation number is 256, the pulse transmission time width is 256us, and the repetition frequency period is 2000 us.
In the invention, when the ranging frame is switched to the speed measurement frame, the echo signal can be received only by waiting for L repetition frequencies because of speed ambiguity, wherein L is round (R/125 is 150), R is the target actual distance, and round is an upward rounding operation. Since the target distance is 300km maximum and Lmax is 16, the tachometer frame starts pulse accumulation from the 17 th repetition frequency and the ranging frame starts pulse accumulation from the 2 nd repetition frequency.
As shown in fig. 4, a working state of the inter-frame switching control unit in the application method for resolving the velocity ambiguity based on the pulse accumulation frame dual-frequency method includes the following steps:
a1, the interframe switching control unit controls the radar to work in a ranging frame work mode through a synchronous pulse, signal transmission and echo reception are completed in each repetition frequency period, data are written into an SRAM1 after pulse compression, and the current repetition frequency echo data are processed and then jump to A2;
a2, judging whether the pulse accumulation unit finishes 256 effective pulse accumulations, if so, jumping to the step A3, and if not, jumping to the step A1 to continue execution;
a3, setting a next frame type mark 0x55, updating a speed measurement frame repetition frequency period, and jumping to the step A4;
a4, the interframe switching control unit controls the radar to work in a speed measurement frame working mode through a synchronous pulse, signal transmission and echo reception are completed in each repetition frequency period, data are written into an SRAM2 after pulse compression, and the current repetition frequency echo data are processed and then jump to A5;
a5, judging whether the pulse accumulation unit finishes 4096 effective pulse accumulations, if so, jumping to step A3, and if not, jumping to A4 to continue executing
A6, setting the next frame type flag to 0xAA, and jumping to step A1.
During the periodic operation of the steps A1-A6, the DSP reads the frame type mark, when the frame type mark is changed from 0xAA to 0x55, the DSP starts to process the ranging frame data, performs two-dimensional plane target detection, and calculates the repetition frequency period without blind area shielding according to the actual distance of the target; and when the frame type mark is changed from 0x55 to 0xAA, processing the speed measurement frame data, and performing two-dimensional plane target detection to obtain the actual target unambiguous speed.
As shown in fig. 5, a working state of the repetition frequency adjustment unit in the method for resolving speed ambiguity based on pulse accumulation frame dual frequency includes the following steps:
b1, waiting for the FPGA to finish ranging frame pulse accumulation, and jumping to the step B2 when the frame type mark is changed from 0xAA to 0x 55;
b2, the DSP reads the ranging frame data, performs coherent accumulation and target detection to obtain unambiguous distance information, and jumps to the step B3;
b3, judging whether the repetition frequency period of the speed measurement frame is finely adjusted, if so, jumping to the step B4, and if not, jumping to the step B7;
b4, keeping the repetition frequency period of the speed measurement frame unchanged;
b5, judging whether the target is reversely folded and falls in a high repetition frequency emission blind area according to the target unambiguous distance calculated in the step B2 and the finely adjusted repetition frequency period of the speed measurement frame, if so, jumping to the step B6, and if not, jumping to the step B10;
b6, reducing the repetition frequency period of the speed measurement frame to 125us, reducing the time width of the transmitted signal to 16us, reducing the distance gate to 4us, recovering to the repetition frequency period of the speed measurement frame before adjustment, and jumping to the step B10;
b7, reducing the repetition frequency period of the speed measurement frame to 125us, reducing the time width of the transmitted signal to 16us, reducing the distance gate to 4us, and jumping to the step B8;
b8, judging whether the target is reversely folded and falls in a high repetition frequency emission blind area according to the target unambiguous distance calculated in the step B2 and the finely adjusted repetition frequency period of the speed measurement frame, if so, jumping to the step B9, and if not, jumping to the step B10;
b9, calculating according to the target non-fuzzy distance R and the speed measurement frame repetition frequency period obtained by calculation in the step B2 according to the following formula to obtain the speed measurement frame repetition frequency period without emission blind area shielding, and jumping to the step B10 after calculation is finished;
firstly, finding out fuzzy order N, N being floor (R/125 x 150), wherein 125us is a repetition frequency period, and 150m is a delay corresponding target distance of 1 us;
then, each repetition frequency period is adjusted by 1.5-2 times according to the fuzzy order N at the time width of 16us during transmission and considering the system design margin;
and finally, the repetition frequency period of the tachograph frame is 125us-16us/N K, K is a coefficient, and 1.5-2 is taken.
B10, completing the repetition frequency period configuration of the speed measurement frame, writing the repetition frequency period configuration into the FPGA, and jumping to the step B11;
b11, finishing the current ranging frame processing.
The invention relates to a double-frequency speed ambiguity resolution system and method based on pulse accumulation frames, which has the working principle that: the tracking radar realizes unambiguous range measurement at low repetition frequency and unambiguous speed measurement at high repetition frequency by changing repetition frequency period between pulse accumulation frame frames, and alternately operates low repetition frequency pulse accumulation and high repetition frequency pulse accumulation through an inter-frame switching module; considering that a long-distance target can be reversely folded into the high repetition frequency pulse, when a transmitting blind area blocks the target, the period of the high repetition frequency is finely adjusted according to the target distance.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (8)
1. A dual-rate ambiguity resolution system based on pulse accumulation frames, comprising: the device comprises a transmitting subsystem, a receiving subsystem, a circulator and an antenna;
the transmitting subsystem further comprises a baseband signal generating module and a microwave transmitting module;
the receiving subsystem further comprises a microwave receiving module, an intermediate frequency receiving module and a signal processing module;
the transmitting subsystem and the receiving subsystem are respectively connected with the antenna through the circulator;
the microwave transmitting module, the baseband signal generating module, the microwave receiving module and the intermediate frequency receiving module receive the synchronous pulse signals output by the signal processing module and carry out receiving and transmitting time sequence synchronization;
the baseband signal generating module generates a Barker code or a linear frequency modulation baseband signal and outputs the Barker code or the linear frequency modulation baseband signal to the microwave transmitting module;
the microwave transmitting module is used for mixing the received baseband signals, modulating the baseband signals to a microwave frequency band, amplifying the power of the baseband signals and outputting the baseband signals to the circulator;
the microwave receiving module down-converts the received echo signal from a microwave frequency band to an intermediate frequency and outputs the signal to the intermediate frequency receiving module;
the intermediate frequency receiving module performs intermediate frequency signal gain control and controls the amplitude level of the intermediate frequency signal output to the signal processing module within a proper range;
the signal processing module adjusts the pulse repetition frequency between frames according to the type of the pulse accumulation frame, alternately completes the accumulation of a speed measurement frame with high repetition frequency and the accumulation of a distance measurement frame with low repetition frequency, generates corresponding synchronous pulse signals and outputs the synchronous pulse signals to other modules, and simultaneously completes the functions of signal acquisition, pulse compression accumulation and target detection;
the signal processing module completes the detection of the ranging frame target through a repetition frequency adjusting unit, obtains target non-fuzzy distance information, judges whether the target falls in a speed measuring frame emission blind area, finely adjusts a speed measuring frame repetition frequency period if the target falls in the emission blind area, and avoids the target being reversely folded into the emission blind area.
2. The dual-rate ambiguity resolution based on pulse accumulation frame of claim 1, wherein the signal processing module further comprises an a/D sampling unit, a digital down-conversion unit, a pulse compression unit, a pulse accumulation unit, an inter-frame switching control unit, a target detection unit;
the A/D sampling unit performs band-pass digital-to-analog conversion on the intermediate frequency signal and then caches data in an FIFO;
the digital down-conversion unit digitally mixes the intermediate frequency signal to a baseband, performs low-pass filtering, and performs extraction according to the signal bandwidth;
the pulse compression unit performs pulse compression on the Barker code or the linear frequency modulation signal, so that the distance resolution is improved;
the pulse accumulation unit ping-pong stores the data after pulse pressure into two external SRAMs;
the target detection unit ping-pong reads the two-dimensional plane data after pulse pressure from the SRAM;
and the interframe switching control unit adjusts the pulse repetition frequency among the interframes according to the type of the pulse accumulation frame, and alternately completes the accumulation of the speed measurement frame with high repetition frequency and the accumulation of the distance measurement frame with low repetition frequency.
3. The dual-frequency speed-ambiguity resolution system based on pulse accumulation frames as claimed in claim 2, wherein said digital down-conversion unit, pulse compression unit, pulse accumulation unit and inter-frame switching control unit are implemented in FPGA chip; the target detection unit and the repetition frequency adjustment unit are realized in a DSP chip.
4. The dual rate ambiguity resolution system based on pulse accumulation frame as claimed in claim 2, wherein said ranging frame pulse repetition frequency is F, signal transmission time width is T1, range gate time width is T2, pulse accumulation number is M, said tachometer frame pulse repetition frequency is F N, signal transmission time width is T1/N, range gate time width is T2/N, pulse accumulation number is M N, ambiguity order N is a power of 2 relationship.
5. The dual-rate ambiguity resolution system based on pulse-accumulation frames as claimed in claim 4, wherein the distance of the unambiguous distant target measured by the ranging frame is a target distance R, the target distance is reflected in the tachometer frame for a plurality of times, and the target distance R is modulo by C/2/(F x N) at a position R' of the tachometer frame; if the result of dividing the modulus value by (C/2) is smaller than the transmission signal time width T1/N, C is the speed of light, the repetition frequency adjusting unit finely adjusts the repetition frequency period of the speed measurement frame, the product of the adjusting quantity and the coefficient K is larger than the transmission signal time width, K is floor (R/(C/2/(F) N)), and floor is a downward rounding operator.
6. A method for dual-rate ambiguity resolution based on pulse accumulation frame is applicable to any one of claims 1 to 5, and is characterized in that the working state of an inter-frame switching control unit arranged in a signal processing module comprises the following steps:
a1, the interframe switching control unit controls the radar to work in a ranging frame work mode through a synchronous pulse, signal transmission and echo reception are completed in each repetition frequency period, data are written into one of the SRAMs after pulse compression, and the current repetition frequency echo data are processed and then jump to A2;
a2, judging whether the pulse accumulation unit finishes the accumulation of M effective pulses, if so, jumping to the step A3, and if not, jumping to the step A1 to continue the execution;
a3, setting a next frame type mark 0x55, updating a speed measurement frame repetition frequency period, and jumping to the step A4;
a4, the interframe switching control unit controls the radar to work in a speed measurement frame working mode through a synchronous pulse, signal transmission and echo reception are completed in each repetition frequency period, data are written into another SRAM after pulse compression, and the current repetition frequency echo data are processed and then jump to A5;
a5, judging whether the pulse accumulation unit finishes the accumulation of M-N effective pulses, if so, jumping to the step A3, and if not, jumping to the step A4 to continue the execution; the fuzzy order N is a 2-power relation;
a6, setting the next frame type flag to 0xAA, and jumping to step A1.
7. The method for resolving the speed ambiguity based on the dual-frequency of the pulse accumulation frame as claimed in claim 6, wherein during the period operation of steps A1-A6, reading the frame type flag, when the frame type flag changes from 0xAA to 0x55, starting to process the ranging frame data, performing two-dimensional plane target detection, and calculating the repetition frequency period without blind zone shielding according to the actual distance of the target; and when the frame type mark is changed from 0x55 to 0xAA, processing the speed measurement frame data, and performing two-dimensional plane target detection to obtain the actual target unambiguous speed.
8. A method for dual-frequency velocity ambiguity resolution based on pulse accumulation frame is applicable to any one of claims 1 to 5, and is characterized in that the operating state of a repetition frequency adjusting unit arranged in a signal processing module comprises the following steps:
b1, waiting for finishing the accumulation of the ranging frame pulse, and jumping to the step B2 when the frame type mark is changed from 0xAA to 0x 55;
b2, reading ranging frame data, performing coherent accumulation and target detection to obtain unambiguous distance information, and jumping to the step B3; the repetition frequency of the ranging frame pulse is F, the time width of a corresponding transmitting signal is T1, and the time width of a range gate is T2;
b3, judging whether the repetition frequency period of the speed measurement frame is finely adjusted, if so, jumping to the step B4, and if not, jumping to the step B7;
b4, keeping the repetition frequency period of the speed measurement frame unchanged;
b5, judging whether the target is reversely folded and falls in a high repetition frequency emission blind area according to the target unambiguous distance calculated in the step B2 and the finely adjusted repetition frequency period of the speed measurement frame, if so, jumping to the step B6, and if not, jumping to the step B10;
b6, the speed measurement frame is recovered to the speed measurement frame repetition frequency period before adjustment, and the step B10 is skipped;
b7, reducing the repetition frequency period of the tachograph frame to 1/(F N), reducing the time width of the emission signal to T1/N, reducing the range gate to T2/N, and jumping to the step B8; the fuzzy order N is a 2-power relation;
b8, judging whether the target falls in a dead zone of high repetition frequency according to the target unambiguous distance calculated in the step B2 and the repetition frequency period of the speed measurement frame finely adjusted in the step B7, if so, jumping to the step B9, and if not, jumping to the step B10;
b9, calculating according to the target unambiguous distance R and the velocity measurement frame repetition frequency period obtained in the step B2 to obtain a velocity measurement frame repetition frequency period without emission blind area shielding, and jumping to the step B10 after calculation is finished;
b10, completing the repetition frequency period configuration of the speed measurement frame, and jumping to the step B11;
b11, finishing the ranging frame processing.
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