CN101021561A - Wide band rader utilizing multi-transmitting and multi-receiving frequency division signal and imaging method thereof - Google Patents

Abstract

The invention relates to a broadband radar imaging method adopting multi-transmit and multi-receive frequency-division signals, comprising the following steps: 1) M array elements of the radar transmitter synchronously transmit M frequency sub-band signals; 2) the radar receiver consists of N receiving Array element configuration, each receiving array element is provided with M receiving channels corresponding to the above-mentioned M transmitting sub-band signal frequency bands, thereby obtaining M×N echo signals in total; 3) for the M×N echo signals obtained by the receiving array The wave signal is processed to complete the detection of the target, and the multi-channel echo is synthesized into a high-resolution range image in the azimuth and distance of the detected target. The present invention uses multi-channel narrowband signals to synthesize broadband signals through the multi-transmit and multi-receive technology, thereby reducing the requirement for the instantaneous bandwidth of the radar system; at the same time, through the combination of the multi-transmit and multi-receive technology and the array technology, the multi-transmit and multi-receive broadband imaging radar has electronic scanning capabilities, Multi-target detection, tracking and imaging functions can be completed in parallel.

Description

A Broadband Radar and Imaging Method Using Multi-Transmit and Multi-Receive Frequency Division Signals

technical field

The invention belongs to the technical field of radar, in particular, the invention relates to a broadband radar and an imaging method thereof.

Background technique

With the development of radar imaging technology, such as synthetic aperture radar (SAR), inverse synthetic aperture radar (ISAR), and radar identification technology, the distance resolution required by radar is getting higher and higher, so the required radar signal bandwidth is getting higher and higher. bigger and bigger. How to realize the transmission and reception of broadband signals has always been a difficult point in radar system design, and it is also a standard to distinguish many radar working systems. According to different broadband signal generation and signal processing methods, the methods for obtaining broadband signals and high-resolution one-dimensional range images can be divided into three categories: the imaging method using the step frequency hopping system, and the imaging method using the time-frequency conversion (STRETCH) system. An imaging method and an imaging method using a wideband signal pulse compression regime. The radar system using the broadband signal pulse compression processing method requires the transmitter to transmit a signal with an instantaneous bandwidth of up to hundreds of megahertz or even a gigahertz, so system indicators such as the bandwidth of the transmitting and receiving device, dynamic range, and A/D conversion rate and system compensation technology Both put forward very high requirements, and at the same time, high-throughput data processing also puts forward higher requirements for processor processing speed. In order to reduce the cost and demand for device performance, scholars have proposed the first two more practical imaging methods for broadband signals and one-dimensional high-resolution range images.

The time-frequency conversion system (STRETCH) requires the transmitter to transmit a broadband chirp signal, and the receiver generates a chirp signal corresponding to a certain range gate as a reference signal with a certain delay, and mixes the reference signal with the signal in the range gate. frequency, the target echoes at different distances are converted into point-frequency signals of different frequencies due to the difference in time delay. In the system, the resolution of the time delay in the target echo is equivalent to the resolution of the frequency. The disadvantage of this system is: the observation distance is limited, and another narrow-band radar is needed to complete the detection and tracking of the target.

The stepped frequency system (Stepped frequency) is to divide the complete broadband signal into several subbands, each subband is transmitted and received in different transmission periods, and after all subband signals are received, the subband signals are combined into broadband Signal. The disadvantages of this system are: firstly, the sub-band signals are sent and received in time-sharing, and the movement of the target will have a significant impact on the synthesis of the sub-band signals; secondly, the repetition frequency of the radar work is low, which is more likely to cause velocity ambiguity.

On the other hand, in recent years, broadband array technology has extended its tentacles to the field of high-resolution imaging. Compared with the broadband radar using mechanical scanning antenna, the broadband array radar space search speed is fast, and it can form multi-beams to observe the space azimuth target. The current broadband array system mainly includes: a broadband array that transmits an instantaneous wideband narrow pulse signal and uses photoelectricity combined with time delay processing; an array system that transmits a frequency sweep signal and uses a time-frequency conversion (STRETCH) signal processing method; Broadband phased array for FM signals. The main problem with wideband arrays today is the wideband beamforming problem. First, the signal frequency band is very wide. If the signal weighting is only designed according to the center carrier frequency, there will be a problem of beam running, that is, the beam pointing of the edge component of the frequency band is inconsistent with the beam pointing of the center component of the frequency band. Secondly, for the receiving beamforming of broadband signals, it is not enough to adjust the signal phase alone, and the time delay difference of each array element signal must be compensated. For the problem of beam running, it is generally necessary to decompose the broadband signal into several narrowband signals in the frequency domain, and design different weighting coefficients for each narrowband signal. For broadband arrays that need to be adjusted for delay, at present, true delay lines and optical signals for photoelectric conversion are generally used for processing. The cost of this radar is still relatively high.

Contents of the invention

The purpose of the present invention is to combine the idea of multi-transmitting and multi-receiving frequency-division signals with broadband imaging radar, increase the repetition frequency of the radar system to overcome the defect of poor imaging quality of maneuvering targets, and provide A multifunctional radar system capable of simultaneously completing detection, tracking and imaging and an imaging method thereof.

In order to realize the above-mentioned invention object, the wide-band radar that adopts multi-send and multi-receive frequency-division signals provided by the present invention includes an array antenna, a transmitter subsystem and a receiver subsystem connected to the array antenna, and a transmitter subsystem and a receiver subsystem respectively connected to the array antenna. The clock source connected by the subsystem; it is characterized in that, the transmitter subsystem includes M parallel sub-transmitters, and generates M frequency division signals; the receiver subsystem includes N parallel sub-receivers and signal A processor, the sub-receiver is an M channel frequency division parallel receiver.

In the above technical solution, the clock source generates clock excitation signals with M different frequencies.

The broadband radar imaging method that adopts multi-transmit and multi-receive frequency-division signals provided by the present invention comprises the following steps:

1) The M array elements of the radar transmitter transmit M subband signals synchronously;

2) Each receiving array element of the radar receiver is provided with M receiving channels corresponding to the M sub-band signal frequency bands, and N receiving array elements in the receiving array receive echo signals, thereby obtaining M×N echo signals in total Signal;

3) Perform signal processing on the M×N echo signals obtained by the receiving array to complete target detection, and synthesize the detected target echoes into a high-resolution range image.

In the above technical solution, each frequency sub-band signal in the step 1) occupies a certain frequency band range, and each sub-band signal can overlap or not overlap each other in the frequency domain; the entire sub-band signal set can be continuous or discontinuous Cover a bandwidth.

In the above technical solution, the step 1) includes the following sub-steps:

11) The transmitter generates M baseband signals S _m (t), wherein m=1, 2, ..., M; the transmit power, time width and effective bandwidth of each baseband signal can be different or the same;

12) Assign M baseband signals S _m (t) to the 1st to M sub-transmitters in sequence, and each sub-transmitter first modulates S _m (t) to the intermediate frequency f _I ; then after the first mixing , the center frequency of frequency mixing is f _m =f ₀ +Δf _m , where f ₀ represents the center carrier frequency of the first mixing frequency allocated to the first sub-transmitter, and Δf _m represents the relative center frequency of the m-th sub-band signal Increment of the center frequency of the first sub-band signal; at last the sub-band signal is mixed for the second time with f _c to obtain the frequency-divided sub-band signal whose carrier frequency is f _c +f _m +f _I ;

13) The M sub-band frequency-divided signals are transmitted in parallel and synchronously by different sub-transmitters.

In the above technical solution, the step 2) includes the following sub-steps:

21) The receiver adopts an array structure consisting of N array elements, and each array element is provided with M receiving channels; each receiving channel uses a reference signal of a corresponding frequency to mix the echo and down-convert it to the baseband, and then passes through The band-pass filter excludes sub-band signals of other frequency bands, so that each receiving array element obtains M sub-band signals corresponding to M transmitting sub-band signals;

22) Perform zero-IF digital sampling processing and I/Q quadrature dual-channel digital down-conversion processing on the M×N subgrade band signals obtained in step 21), to obtain M×N road echoes that can be used by digital signal processors Signal.

In the above-mentioned technical scheme, described step 3) includes following sub-steps:

31) Receiving beamforming for M×N echo signals to complete the scanning of the observation space;

32) Detect whether there is a target in the direction of forming the receiving beam, store the echo of the target, and complete the tracking of the detected target at the same time;

33) The sub-band signals of different frequency bands are compensated for the time delay and phase difference between the sub-bands through preprocessing; The central frequency differences of the band signals are equal; finally, the inverse Fourier transform is performed on the synthesized broadband signal to obtain a one-dimensional high-resolution range profile.

In the above technical solution, the receiving beamforming of the M×N echo signals in the step 31) is:

The beamforming process is performed on the baseband signals of the same frequency band receiving channel of N different array elements, so that the N×M orthogonal dual-channel signals from N multi-channel frequency division parallel receivers are combined into M azimuth synthesis signals.

In the above technical solution, the step 3) also includes the following sub-steps:

34) The one-dimensional high-resolution range images obtained from multiple observations of the same target are synthesized into two-dimensional high-resolution images by frequency analysis after motion compensation is completed.

In the above technical solution, the method for synthesizing a two-dimensional high-resolution image may use a wavenumber domain algorithm, a Chirp-Scaling algorithm, a Chirp-Z transform algorithm, and a time-frequency analysis method. The broadband radar imaging method of multi-transmitting and multi-receiving frequency division signals is suitable for the field of SAR or ISAR imaging.

The technical effects of the present invention are as follows: the present invention synthesizes wideband signals with narrowband signals through multiple transmission and multiple reception techniques, thereby reducing the requirement for the instantaneous bandwidth of the radar system; at the same time, a new broadband array implementation scheme is obtained by combining multiple transmission and multiple reception techniques with array technology , so that the multi-transmit and multi-receive broadband radar has the ability of electronic scanning, and can complete multi-target detection, tracking and imaging functions in parallel. Compared with the currently used broadband radar signal generation and processing methods, multi-transmit and multi-receive frequency-division signal radars have many advantages: Compared with time-frequency conversion methods, the imaging distance is no longer limited, and at the same time, it is not necessary to use another narrow-band radar Completing the search and tracking functions; compared with the stepping frequency hopping method, the repetition frequency of the multi-transmit and multi-receive broadband radar is higher, which can overcome the defect of poor imaging quality of maneuvering targets; Compared with multi-transmit and multi-receive broadband radar, the performance requirements of transmitting and receiving devices are lower, which is easy to realize.

Description of drawings

Figure 1 is a block diagram of a radar system with multiple transmission and multiple reception systems;

Fig. 2 is a block diagram of the mth road sub-band transmitter;

Fig. 3 is the block diagram of M channel frequency division parallel receiver;

Fig. 4 is a schematic diagram of the time-frequency relationship of the M channel frequency molecular band intermediate frequency signal;

Fig. 5 is a schematic diagram of a multi-transmission multi-reception frequency division broadband radar signal processing flow;

FIG. 6 is a schematic diagram of a receive beamforming processing flow;

Fig. 7 is a schematic diagram of narrowband synthetic wideband signal processing flow;

FIG. 8 is a flow chart of the broadband radar imaging method of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

Figure 1 shows a block diagram of a frequency-division wideband radar system using multiple transmitters and multiple receivers. The radar system of this embodiment is mainly composed of a transmitting/receiving array antenna, a transmitter subsystem, a receiver subsystem, a clock source, a monitoring subsystem and a power supply. The transmitter subsystem of this embodiment includes M parallel sub-transmitters, which generate M-channel frequency division signals in total, and the receiver subsystem includes N parallel sub-receivers and signal processors, and the sub-receivers are M-channel Frequency Division Parallel Receiver. Each component of the radar system of this embodiment is described as follows:

① Transmitting/receiving array antenna: The receiving antenna and the transmitting antenna can share a set of array antenna. At this time, as shown by the dotted line in Figure 1, each extension of the receiver and each extension of the transmitter are connected to the array antenna through a transceiver duplexer. The transceiver duplexer completes the switching of the transmission and reception process, which can well complete the isolation of transmission and reception. At this time, the number M of transmitting array elements is equal to the number N of receiving array elements. However, multi-transmission and multi-reception radars often use sparse arrays in order to obtain better beamforming effects and use space diversity to combat target "flashing". At this time, the same set of array antennas is no longer used for transmission and reception. At this time, M and N may be different.

②Transmitter subsystem: The transmitter has M sub-transmitters in total, which will generate M frequency division signals. Figure 2 shows a block diagram of a sub-transmitter. Combined with Figure 2, the workflow of the sub-transmitter is:

Step 11: Under the control of the system clock, the digital frequency synthesizer is controlled by the excitation source to generate the baseband signal. For example, the mth subgrade band signal is S _m (t), its time width is T _m , and its effective bandwidth is B _m , where m=1, 2, . . . , M. The transmit power, time width and effective bandwidth of each baseband signal may be the same or different from each other. The forms of the signals may also be different from each other.

Step 12: Perform frequency mixing twice on the m-th baseband signal. First, the baseband signal S _m (t) is modulated to the intermediate frequency f _I , and then mixed for the first time. The center frequency of the mixing is f _m =f ₀ +Δf _m , where f ₀ means that it is allocated to the first channel for transmission The first mixing center carrier frequency of the machine, that is, the lowest first mixing center carrier frequency among all sub-band signals, Δf _m represents the center frequency of the m-th sub-band signal relative to the center frequency of the first sub-band signal Increment; the subband signal is then mixed a second time with _fc , where _fc is the carrier frequency of the radar's radio frequency part. After the above process, the carrier frequency of the sub-band frequency division signal finally transmitted by the mth sub-transmitter is f _c +f _m +f _I .

Step 13: Send the mixed high-frequency signal to the high-frequency amplifier, amplify it and send it to the transmitting antenna.

③ Receiver subsystem: The receiver has a total of N channels of receivers. Each sub-receiver has M receiving channels, and this sub-receiver is referred to as M frequency-division parallel receivers in the present invention, as shown in FIG. 3 . The N receiving array elements in the receiving array receive echo signals. Each receiving element is equipped with M receiving channels, and each receiving channel uses a reference signal of a different frequency to mix the echo and down-convert it to the baseband, so that the center frequency of each sub-band signal is zero, that is, zero An intermediate frequency sub-band signal; the down-converted signal is passed through a low-pass filter to exclude sub-band signals in other frequency bands, so as to obtain M baseband signals corresponding to the M transmit sub-band signals. After the above processing, the entire receiving array obtains N×M subgrade band signals in total. The N×M subgrade band signals are distinguished by different frequency bands and different array elements. The working process of the receiver of the m-th channel is now introduced in combination with FIG. 3 , and the rest of the channels are the same.

Step 21: Send the signal from the receiving element to the low noise amplifier to obtain a high signal-to-noise ratio.

Step 22: First Mixing. The local oscillator of the mixing frequency is a highly stable local oscillator (that is, a local oscillator), and the medium

The heart frequency is f _c , and a filter is provided, the center frequency of the passband is f _m , and the bandwidth of the passband is the effective bandwidth B _m of the mth sub-band signal;

Step 23: Second Mixing. The center frequency of the multi-channel receiver mixing local oscillator corresponds to the center frequency of each sub-band signal, for example, the second mixing frequency of the m-th receiving channel is f _m ;

Step 24: Perform bandpass filtering. The passband bandwidth of the bandpass filter is B _m ;

Step 25: Perform intermediate frequency A/D sampling;

Step 26: digital quadrature down-conversion to generate I/Q dual-channel digital signals, and finally generate M orthogonal dual-channel digital signals, the center carrier frequency of which is f _I ;

Step 27: Sending the data to a digital signal processor for beam forming, target detection and tracking, and target imaging.

④Other subsystems include clock source, monitoring subsystem and power supply. The clock source is different from the conventional radar system in that it generates M clock signals with different frequencies. In the transceiver mechanism of the present invention, the receiving array element is synchronized with the transmitting array element. Each transmitting array element transmits different or partially identical sub-band signals in parallel or partially in parallel according to needs, and each receiving array element can receive all signals or selectively receive part of the signal, and each receiving array element is equipped with multiple channels corresponding to different sub-band signals. Receiver with signal, each receiver works in the corresponding narrowband frequency band. Other parts are the same as the conventional pulse radar system.

As shown in Fig. 8, the imaging method of the present invention adopts the frequency division broadband radar of multi-transmission and multi-reception including the following steps:

Step 1: Launch step. At the radar transmitting end, M subband signals are synchronously transmitted from the M transmitting array elements of the transmitting array. Figure 4 shows the time-frequency relationship of the multi-subband baseband signals used by the transmitting array element in this embodiment, described as follows:

The sub-band signal set used by the radar of this embodiment is a frequency-division signal set, and each sub-band occupies a certain frequency band range, but each sub-band signal can overlap or not overlap each other in the frequency domain; the entire sub-band set can be continuous or intermittent The ground covers a large bandwidth; each sub-band signal can adopt a linear frequency modulation signal structure, or a non-linear frequency modulation structure and other modulation methods; each sub-band can use the same modulation method, or use a different modulation method. In addition, the radar of the present invention employs a pulse system.

The transmission method of this embodiment is as follows: the frequency-division signal set is an orthogonal frequency-division signal set, the baseband forms of all subband signals in the set are identical to each other, and each subband signal is modulated on a carrier frequency of a different frequency. The radar system assigns different sub-band signals to different transmitting elements in one-to-one correspondence. All transmitting array elements transmit sub-band signals at the same time. The specific radar signal transmission process is as described in step 11 to step 13, and will not be repeated here.

Step 2: Receive step. At the radar receiving end, N receiving elements in the receiving array receive echo signals. Each receiving array element is equipped with M receiving channels, and each receiving channel uses a reference signal of a different frequency to mix the echo and down-convert it to the baseband, even if the center frequency of the sub-band signal is zero; the down-converted signal Subband signals of other frequency bands are excluded through a low-pass filter, so as to obtain M baseband signals corresponding to M transmitted subband signals. After the above processing, the entire receiving array obtains N×M subgrade band signals in total. The N×M subgrade band signals are distinguished by different frequency bands and different array elements.

The specific receiving process of the radar signal in this step is described in step 21 to step 27, and will not be repeated here.

Step 3: Signal processing step. The N×M subgrade band signal obtained by the receiving array is input to the signal processing equipment to complete the target detection, and the detected target echo is synthesized into a high-resolution range image.

This step is completed in the signal processor, and the signal processor of the present invention is located behind the M channel frequency division parallel receiver. The receiver subsystem separates the signal received by the receiving array into N×M orthogonal dual-channel digital baseband signals after primary frequency conversion, secondary frequency conversion, and zero-IF sampling processing, and inputs them into the signal processor. The processing procedure of signal processor is as shown in Figure 5, and a preferred embodiment of this process comprises the steps:

Step 31: Divide sectors, each sector corresponds to an orientation parameter. Select an azimuth parameter, and perform beamforming processing on the baseband signals of the same frequency band receiving channel of N different array elements, so as to combine the N×M orthogonal dual-channel signals from N multi-channel frequency division parallel receivers into M channels Azimuth composite signal.

The specific method of this step is shown in Figure 6 and described as follows:

Input signals of the same frequency band from different array elements into the same DBF (that is, digital beamforming) processing unit;

Each DBF processing unit sets a weighted value according to a frequency band of a corresponding signal, so as to suppress beam running of the broadband array. For example, the signal frequency corresponding to the mth DBF receiver is f _dm =f _m +f _c +f _I , and assuming that the array is a uniform linear array, the array element spacing is d, and the azimuth angle to be scanned is θ, using uniform weighting, Then the weighted value vector of the DBF of this road is

$<span\; class="notranslate">\; \&lsqb;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; dm</span>}}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; dm</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \&rsqb;</span><span\; class="notranslate">\; \&rsqb;</span><span\; class="notranslate">\; ,</span>$

Among them, c represents the wave propagation speed.

Output the signals corresponding to the scanning azimuths (combined azimuth signals) of the M channels of the M DBF units.

Step 32: Perform target detection on the currently selected azimuth. This step is to complete the target signal detection by using the beamformed M-channel azimuth synthesis signal corresponding to a certain azimuth, that is, to detect whether the target exists and how far the target is from the radar. In a preferred embodiment, the multi-transmission and multi-reception radar first uses each of the M-way azimuth synthesis signals to complete the detection, and then performs non-coherent accumulation of the detected detection variables, or uses the distributed detection method to detect the M-way azimuth synthesis signals. The results are combined to improve the detection performance of the radar.

The detection method in this step can adopt the principle of non-coherent accumulation or distribution detection.

Step 33: Judging whether there is a target in the currently selected orientation. If there is a target, go to step 34; if there is no target, go to step 38.

Step 34: Store the target's azimuth parameter, distance parameter, and the M-path combined azimuth signals obtained in step 32 corresponding to the azimuth of the target. It is worth noting that there may be multiple targets at different distances in the same azimuth, and at this time, the signals in the multiple range gates corresponding to the targets need to be stored separately.

Step 35: extracting the M-path combined azimuth signals stored in step 34, and compensating the M-path combined azimuth signals according to the direction of the target. The purpose of compensation is to eliminate the phase difference and delay difference of the M signals caused by the position difference of the transmitting array, and then correlate the signals to obtain a high-resolution range image.

The compensation processing process is as follows: transform the M-channel azimuth synthesis signal into the frequency domain; use the sub-band signal correlation processing to estimate the position of the target in the receiving beam as the initial value, and then use the iterative estimation method to estimate the more accurate azimuth of the target; The entire effective width of the receiving beam is equally divided into M strips, and a weight vector is generated according to the strip where the target is located, and the spectrum of each sub-band is weighted.

Step 36: Merge the M-channel azimuth composite signals obtained in Step 35 into broadband signals, and then obtain a one-dimensional high-resolution range image. The principle of wideband synthesis in the present invention is: divide a complete wideband signal into several narrowband signals, and transmit and receive them respectively, each transmission and receiver are narrowband, and these narrowband signals are recovered by frequency shift The original appearance of its broadband signal.

The specific method is shown in Figure 7:

Firstly, the preprocessed sub-band signals of the M channels are matched and filtered separately, and the output of the matched filter is passed through a low-pass filter. The bandwidth of the low-pass filter is the effective bandwidth of the transmitted sub-band signal, for example, corresponding to the m-th sub-band signal The bandwidth of the m-th subband receiver is B _m .

Secondly, the corresponding frequency shift will be performed on the obtained matched filtering signal. The purpose of the frequency shift process is to synthesize multiple narrowband signals into wideband signals, that is, to restore the spectrum structure between the transmitted subband signals. For example, the frequency shift amount of the m-th sub-band is Δf _m , that is, the frequency spectrum of the m-th path is shifted by Δf _m along the frequency axis.

Finally, the frequency-shifted sub-band signal spectrum is added to synthesize the wideband signal spectrum; spectrum compensation is performed, and a one-dimensional high-resolution range profile can be obtained through inverse Fourier transform, and stored.

Step 37: Two-dimensional imaging processing. Combine the one-dimensional high-resolution range images of the corresponding azimuths and distance targets stored in several repeated cycles before this processing cycle, and obtain the two-dimensional high-resolution image of the target according to the SAR or ISAR imaging principle. For example, for ISAR radar, the receiver performs translation compensation on the one-dimensional high-resolution range image obtained in different repetition frequency periods, that is, envelope alignment and phase correction, and further obtains the two-dimensional high-resolution image of the target through the method of frequency analysis. At this point, this step is the same as the traditional ISAR imaging process.

After this step ends, go to step 38.

Step 38: Judging whether all azimuths have been detected, if it is judged to be yes, then end this processing cycle; if it is judged to be no, select the next azimuth, and return to step 31 for beamforming processing.

In addition, the order of steps 32, 33, and 34 in this embodiment can be changed, which is easily understood by those skilled in the art.

Claims (10)

1, a kind of wideband radar that adopts the multi-sending and multi-receiving frequency division signal comprises array antenna, transmitter subsystem that is connected with array antenna and receiver subsystem, and the clock source that is connected with the receiver subsystem with the transmitter subsystem respectively; It is characterized in that described transmitter subsystem comprises M parallel sub-transmitter, common property is given birth to M road frequency division signal; Described receiver subsystem comprises N parallel slave receiver and signal processor, and described slave receiver is a M road frequency division parallel receiver.

By the wideband radar of the described employing multi-sending and multi-receiving frequency division of claim 1 signal, it is characterized in that 2, described clock source produces the clock drive signal of M different frequency.

3, a kind of wideband radar formation method that adopts the multi-sending and multi-receiving frequency division signal comprises the steps:

1) M frequency division subband signal of the M of radar transmitter subsystem array element synchronized transmissions;

2) the radar receiver subsystem adopts the receiving array structure, and total N receives array element, and each receives array element M the receiving cable corresponding to described M subband signal frequency range is set, and makes the radar receiver subsystem obtain M * N road echoed signal altogether;

3) M * N road echoed signal that is obtained by the radar receiver subsystem is carried out signal Processing, finish the detection of target, and detecting on target direction and the distance the synthetic High Range Resolution of multichannel target echo.

4, by the wideband radar formation method of the described employing multi-sending and multi-receiving frequency division of claim 3 signal, each the frequency division subband signal in the described step 1) occupies certain spectral range, each subband signal frequency domain can be overlapped can be not overlapping yet; Whole subband signal collection can also can have continuously and covers a broadband frequency range discontinuously.

5, by the wideband radar formation method of the described employing multi-sending and multi-receiving frequency division of claim 3 signal, comprise following substep in the described step 1):

11) transmitter produces M baseband signal s _m(t), m=1 wherein, 2 ..., M; The emissive power of each baseband signal, the time wide and effective bandwidth can be different also can be identical;

12) with M baseband signal s _m(t) number distribute to the 1st to M sub-transmitter in regular turn, each sub-transmitter is at first with s _m(t) be modulated to IF-FRE f _IPass through mixing for the first time again, the centre frequency of mixing is f _m=f ₀+ Δ f _m, f wherein ₀The mixing first time center carrier frequence of the 1st way transmitter, Δ f are distributed in expression _mRepresent the increment of the centre frequency of m way band signal with respect to the centre frequency of first via subband signal; Use f at last _cSubband signal is carried out the mixing second time, and obtaining carrier frequency is f _c+ f _m+ f _IEmission subband frequency division signal;

13) with M subband frequency division signal, by the parallel emission of the sub-transmitter of difference.

6, comprise following substep by the wideband radar formation method of the described employing multi-sending and multi-receiving frequency division of claim 3 signal, described step 2):

21) receiver adopts array structure, and N array element is arranged, and each array element is provided with M receiving cable;

Each receiving cable adopts the reference signal of corresponding frequencies that echo is carried out mixing and it is down-converted to base band, get rid of the subband signal of other frequency ranges through bandpass filter then, obtain and M the corresponding M roadbed of emission subband signal band signal thereby make each receive array element;

22) to step 21) the middle M * N roadbed band signal that obtains, carry out zero intermediate frequency digital sample and the Digital Down Convert of I/Q orthogonal double channels, acquisition can be for the M * N road echoed signal of digital signal processor use.

7, by the wideband radar formation method of the described employing multi-sending and multi-receiving frequency division of claim 3 signal, comprise following substep in the described step 3):

31) received beam to M * N road echoed signal forms, to finish the scanning to observation space;

32) on the direction that forms received beam, detect whether there is target, and the echo of target is stored, finish simultaneously detecting the tracking of target;

33) with the subband signal of different frequency range time delay and phase differential by pre-service compensation intersubband; Then with the frequency spectrum shift of subband signal with synthesized wideband signal, wherein the centre frequency difference equates between the difference of each intersubband amount of moving and corresponding emission subband signal; At last synthesized wideband signal is done matched filtering, thereby obtain the one dimension High Range Resolution.

8, by the wideband radar formation method of the described employing multi-sending and multi-receiving frequency division of claim 7 signal, described step 31) received beam of M * N road echoed signal formed and is:

The baseband signal of N the same frequency range receiving cable of different array elements is done wave beam form processing, thereby will merge into orientation, M road composite signal from the N * M road orthogonal double channels signal of N multichannel frequency division parallel receiver.

9, by the wideband radar formation method of the described employing multi-sending and multi-receiving frequency division of claim 7 signal, also comprise following substep in the described step 3):

34) will repeatedly observe the one dimension High Range Resolution that obtains after finishing motion compensation to same target, by the synthetic two-dimentional high resolution picture of the method for frequency analysis.

10, by the wideband radar formation method of the described employing multi-sending and multi-receiving frequency division of claim 9 signal, the method for described synthetic two-dimentional high resolution picture can adopt Wavenumber Domain Algorithms, Chirp-Scaling algorithm, Chirp-Z mapping algorithm or time frequency analysis method.

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