Method and device for digital implementation of a phased array radar unit based on initial phase modulation

Abstract

The application discloses a kind of based on initial phase modulation phased array radar unit digitization implementation method and device, method includes the following steps: initial phase modulation is carried out to each antenna unit transmission pulse;Echo data pre-processing;Target phase accumulation and beam forming.This application is unchanged on the basis of reserving traditional digital phased array radar structure, only needs wave control to change the initial phase of each antenna transmission pulse, can equivalent realization unit level digitization function, with miniaturization, light weight and low power consumption ability, and not limited by radar operating frequency range.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, and in particular relates to a method and apparatus for digitally implementing a phased array radar unit based on initial phase modulation. Background Technology

[0002] Digital array radar offers advantages such as flexible beamforming, strong anti-interference capabilities, and excellent clutter suppression. Each antenna element in a digital array radar has its own receiving channel and A / D converter, thus exhibiting high reconfigurability. The unit digitization components, such as... Figure 1 As shown.

[0003] Due to the high cost and power consumption of radar T / R components and A / D converters, digital array radars are difficult to miniaturize, lighten, and reduce power consumption. Furthermore, due to antenna size limitations, only low-frequency bands (such as the P-band) can currently achieve unit digitization. For high frequencies such as the Ku and Ka bands, unit digitization cannot be achieved due to back-end size limitations. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a digital implementation method for phased array radar units based on initial phase modulation, comprising the following steps:

[0005] (10) Perform initial phase modulation on the transmitted pulse of each antenna element:

[0006] For a phased array radar with subarray digitization, the radar transmits K pulses in each coherent accumulation time. First, the wave control unit of the subarray generates a random phase value for each antenna element. When transmitting pulses, the generated random phase is modulated into the transmitted signal and then radiated out from the antenna element.

[0007] (20) Echo data preprocessing:

[0008] For a subarray digital radar, after each digital channel receiver receives the echo data, it undergoes amplification, down-conversion, filtering, A / D conversion, and pulse compression to obtain K pulse echo signals within a coherent accumulation time.

[0009] (30) Target coherent accumulation and beamforming:

[0010] The prior phase information is used to compensate and coherently accumulate the K pulse echo signals. For the echo signal of the m-th antenna element, since the phase was correctly compensated before coherent accumulation, it is accumulated during the coherent accumulation process, while the echoes of the other antenna elements are suppressed as sidelobes during accumulation. Thus, the echo signal of the m-th antenna element is separated. The separated element signals are digitally beamformed and the spatial domain is set according to the system settings.

[0011] Furthermore, step (10) specifically includes:

[0012] (11) Generate random phase values:

[0013] Assuming each channel has M antennas, the random phase value of the m-th antenna element is... in Solve for a length of K using the following optimization function.

[0014]

[0015]

[0016] Where F is the number of FFT points;

[0017] (12) Initial phase modulation of the transmitted signal: K pulses are transmitted within each coherent accumulation phase of the radar. Assume the transmitted signal of the kth pulse is... Assume the transmitted signal is a linear frequency modulated signal:

[0018]

[0019] in Let f0 be a rectangular window function, where f0 is the carrier frequency of the transmitted signal; μ = B / τ represents the frequency modulation slope, B is the signal bandwidth, and τ is the signal duration; The modulated signal is obtained by adding initial phase modulation.

[0020]

[0021] Finally, the signal Radiation is emitted from the m-th antenna element, and a total of K pulses are required for each coherent accumulation cycle.

[0022] Furthermore, the echo data preprocessing step (20) includes:

[0023] (21) Signal Reception: Assuming the target distance from the radar is R0, the radar receives K pulses within one coherent accumulation time, where the echo of the kth pulse is...

[0024]

[0025] Where σ0 represents the scattering coefficient of the target, and c represents the speed of light;

[0026] (21) Amplify, downconvert, filter, and perform A / D operations on the signal:

[0027] The echo signal r of the kth pulse k Superimposed signals from M antenna elements in r represents the echo of the k-th pulse received by the m-th antenna element. else Represents other echoes and noise in space;

[0028] After A / D conversion, the time-domain sampling matrix is ​​obtained, and the echo can be represented as:

[0029]

[0030] Where N is the number of sampling points of the gate, K is the number of pulses in the coherent accumulation time, and r is included in the formula. k,n This represents the sampled value at the nth time point of the kth pulse, where 1 ≤ k ≤ K and 1 ≤ n ≤ N;

[0031] (22) Pulse compression: A matching signal for a linear frequency modulated radar wave is generated according to the radar parameters. Each pulse echo is then subjected to pulse compression processing to obtain a pulse compression matrix signal.

[0032]

[0033] in, This represents the pulse pressure result at the nth time point of the kth pulse.

[0034] Furthermore, the (30) target coherent accumulation and beamforming step includes:

[0035] (31) Phase compensation: using random phase values Compensation is performed on the echoes of K pulses. When it is necessary to separate the signal of the m-th antenna element, the echo after pulse compression is... Random phase added by the upper compensation The echo R of the m-th unit is obtained. m It can be represented as:

[0036]

[0037] in The sampled values ​​of the k-th pulse and the n-th distance scale after phase compensation for the m-th unit are given. N is the number of sampling points of the gate, and K is the number of pulses in the coherent accumulation time;

[0038] (32) Coherent accumulation: The echoes of K pulses from the same range cell are weighted and superimposed to form a peak value in the corresponding Doppler frequency channel; the input signal is the echo pulse train after phase compensation; the output signal of the same range cell after coherent processing is:

[0039]

[0040] Where p represents the p-th Doppler channel, 0≤p≤K-1. This represents the sampled value of the p-th Doppler channel and the n-th distance scale of the m-th antenna element;

[0041] (33) Beamforming: For different operating modes, operating frequencies, amplitude indices, and beam directions, the amplitude and phase weights of each digital channel are obtained from the index table, and multiple beams are formed to meet the needs of search, tracking, identification, and auxiliary beams under different operating modes; based on the existing channel weighting coefficients, the beamforming result can be expressed as:

[0042]

[0043] Where w m,p Represents the beamforming weighting coefficients. Represents the antenna elements participating in beamforming. Configure according to system requirements.

[0044] Preferably, the initial phase The value is an integer. The optimal solution of the optimization function in step (11) is obtained through offline search.

[0045] Preferably, in step (32), since the phase of the echo of the other antenna elements cannot be correctly compensated, it is distributed on the sidelobe during coherent accumulation, and is suppressed by windowing in the later stage.

[0046] A device for digitally realizing phased array radar units based on initial phase modulation is also provided, including an initial phase modulation module, an echo data processing module, and a target coherent accumulation and digital beamforming module. The device realizes the digitization of phased array radar units according to any of the above methods.

[0047] Compared with the prior art, the advantages of this invention are as follows:

[0048] (1) Based on the traditional digital phased array radar structure, this invention can achieve equivalent unit-level digital functions by simply changing the initial phase of the transmitted pulse of each antenna. It has the capabilities of miniaturization, lightweighting and low power consumption, and is not limited by the radar operating frequency band.

[0049] (2) This invention adds a random phase value before the antenna transmits the signal, performs phase compensation and coherent accumulation on the received signal, and separates the echo signal of the corresponding antenna element. It is easy to implement in engineering and can be applied in radar in multiple fields. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of a unit digital component.

[0051] Figure 2This is a schematic diagram illustrating the digital implementation principle of a phased array radar unit based on initial phase modulation, according to an embodiment of the present invention.

[0052] Figure 3 This is a flowchart of a method for digitally implementing a phased array radar unit based on initial phase modulation, according to an embodiment of the present invention.

[0053] Figure 4 This is a flowchart of the initial phase modulation of the transmit pulse according to an embodiment of the present invention.

[0054] Figure 5 This is a flowchart of echo data processing according to an embodiment of the present invention.

[0055] Figure 6 This is a flowchart of target coherent accumulation and beamforming in an embodiment of the present invention. Detailed Implementation

[0056] To address the challenges of miniaturization, lightweighting, and low power consumption in current digital array radars, this invention, starting from waveform design, adds initial phase modulation to the transmitted pulse. After separating the signals of each antenna element through back-end information processing, spatial beamforming is performed, achieving the ability to digitize elements on a subarray digital radar.

[0057] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0059] Assuming the radar has N digital channels, with four antennas sharing a single T / R module in each channel, taking one channel as an example, each coherent accumulation time requires the transmission of K pulses. First, the beam control generates four sets of phase values ​​of length K. Each antenna is assigned one set of random phase values. The corresponding phase value is modulated in the K pulses transmitted by each antenna. After the receiver amplifies, down-converts, filters, performs A / D conversion, and pulse compression on the received signal, it obtains K pulse echoes. Using the prior phase information of each antenna element, phase compensation and coherent accumulation are performed on these K pulses, allowing the separation of the echo information from the corresponding antenna. Finally, beamforming is performed on the separated 4N antenna echo data. The principle of digital implementation of a phased array radar unit based on initial phase modulation is as follows: Figure 2 As shown.

[0060] Based on the above principles, this embodiment presents a method for digitally implementing a phased array radar unit based on initial phase modulation, such as... Figure 3 As shown, it includes the following steps:

[0061] (10) Initial phase modulation of the transmitted pulse for each antenna element: For a phased array radar with subarray digitization, the radar transmits K pulses per coherent accumulation time. First, the wave control unit of the subarray generates a random phase value for each antenna element. When transmitting the pulse, the generated random phase is modulated onto the transmitted signal and then radiated from the antenna element, such as... Figure 4 As shown, the specific steps include:

[0062] (11) Generating random phase values: Assuming each channel has M antennas, the random phase value of the m-th antenna element is... in Solve for a length of K using the following optimization function.

[0063]

[0064]

[0065] Since the above function is an NP-hard problem, the optimization function needs to be solved by searching, which can be done offline.

[0066] (12) Initial phase modulation of the transmitted signal: K pulses are transmitted within each coherent accumulation phase of the radar. Assume the transmitted signal of the kth pulse is... Without loss of generality, we assume here that the transmitted signal is a linear frequency modulated signal:

[0067]

[0068] in Let f0 be a rectangular window function, t be the carrier frequency of the transmitted signal, and μ = B / τ be the transmission time of the transmitted signal. μ represents the frequency modulation slope, B is the signal bandwidth, and τ is the signal duration. The modulated signal is obtained by adding initial phase modulation.

[0069]

[0070] Finally, the modulated signal Radiation originates from the m-th antenna element. A total of K pulses are required for each coherent accumulation cycle, where e represents the exponential operation.

[0071] (20) Echo data preprocessing: For subarray digital radar, after each digital channel receiver receives the signal, it undergoes amplification, down-conversion, filtering, A / D conversion, and pulse compression to obtain K pulse echo signals within a coherent accumulation time, such as Figure 5 As shown, the specific steps include:

[0072] (21) Signal Reception: Assuming the target distance from the radar is R0, the radar receives K pulses within one coherent accumulation time, where the echo of the kth pulse is...

[0073]

[0074] Where σ0 represents the scattering coefficient of the target, and c represents the speed of light.

[0075] (21) Amplification, downconversion, filtering, A / D: Taking the M-channel T / R component as an example, the echo signal r of the k-th pulse k Superimposed signals from M antenna elements in r represents the echo of the k-th pulse received by the m-th antenna element. else This represents other echoes and noise in space.

[0076] After A / D conversion, the time-domain sampling matrix is ​​obtained, and the echo can be represented as:

[0077]

[0078] Where N is the number of sampling points of the gate, K is the number of pulses in the coherent accumulation time, and r k,n Let represent the sampled value at the nth time point of the kth pulse, where 1 ≤ k ≤ K and 1 ≤ n ≤ N.

[0079] (22) Pulse compression: A matching signal for a linear frequency modulated radar wave is generated according to the radar parameters. Each pulse echo is then subjected to pulse compression processing to obtain a pulse compression matrix signal.

[0080]

[0081] in This represents the pulse compression result at the nth time point of the kth pulse. Since the pulse compression is processed linearly, It can be equivalent to the superposition of the individual pulse compression results of the echoes on M antenna elements.

[0082] (30) Target Coherent Accumulation and Beamforming: Prior phase information is used to compensate for and coherently accumulate the echoes of K pulses. For the echo signal of the m-th antenna element, since the phase was correctly compensated before coherent accumulation, it is accumulated during the coherent accumulation process. The echoes of the other antenna elements are suppressed as sidelobes during accumulation, thus correctly separating the echo signal of the m-th antenna element. Digital beamforming is performed on the separated element signals, and the spatial domain is set according to the system settings, such as... Figure 6 As shown, the specific steps include:

[0083] (31) Phase compensation: using random phase values Compensation is performed on the echoes of K pulses. If it is necessary to separate the signal of the m-th antenna element, then the echo after pulse compression is... Random phase added by the upper compensation The echo R of the m-th unit is obtained. m It can be represented as:

[0084]

[0085] in The sampled values ​​of the k-th pulse and the n-th distance scale after phase compensation for the m-th unit are given. N is the number of sampling points of the gate, and K is the number of pulses in the coherent accumulation time.

[0086] (32) Coherent Accumulation: Coherent accumulation weights and superimposes the echoes from K pulses within the same range cell, forming a peak value in the corresponding Doppler frequency channel. The input signal is the echo pulse train after phase compensation. For the same range cell, the output signal after coherent processing is:

[0087]

[0088] Where p (0≤p≤K-1) represents the p-th Doppler channel, This represents the sampled value of the p-th Doppler channel and the n-th distance scale of the m-th antenna element. Since the phase of the echoes from the other antenna elements cannot be correctly compensated, they are distributed onto the sidelobes during coherent accumulation, which can be suppressed by methods such as windowing.

[0089] (33) Beamforming: For different operating modes, operating frequencies, amplitude indices, and beam directions, the amplitude and phase weights of each digital channel are obtained from the index table, simultaneously forming multiple beams to meet the search, tracking, identification, and auxiliary beam requirements under different operating modes. Based on the existing channel weighting coefficients, the beamforming result can be expressed as:

[0090]

[0091] Where w m,p Represents the beamforming weighting coefficients. The antenna elements that participate in beamforming can be flexibly configured according to system requirements.

[0092] This embodiment also provides a device for digitalizing phased array radar units based on initial phase modulation, including an initial phase modulation module, an echo data processing module, and a target coherent accumulation and digital beamforming module. The device realizes the digitization of phased array radar units based on the above method.

[0093] To address the problems of high cost and high power consumption in current digital array radars, this invention provides a digital implementation method for phased array radar units based on initial phase modulation. While retaining the traditional digital phased array radar structure, it only requires beacon control to change the initial phase of the transmitted pulse of each antenna to achieve equivalent unit-level digital functions. It has the capabilities of miniaturization, lightweighting, and low power consumption, and is not limited by the radar operating frequency band.

[0094] This invention adds a random phase value before the transmitted signal to the antenna, performs phase compensation and coherent accumulation on the received signal, and separates the echo signal of the corresponding antenna element. It is easy to implement in engineering and can be applied in radar in multiple fields.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for digitally implementing a phased array radar element based on initial phase modulation, characterized in that, Includes the following steps: (10) Perform initial phase modulation on the transmitted pulse of each antenna element: For a phased array radar with subarray digitization, the radar transmits K pulses in each coherent accumulation time. First, the wave control unit of the subarray generates a random phase value for each antenna element. When transmitting pulses, the generated random phase is modulated into the transmitted signal and then radiated out from the antenna element. The specific steps (10) include: (11) Generate random phase values: Assuming each channel has M antennas, the random phase value of the m-th antenna element is... ,in , , Solve for the length K using the following optimization function. : Where F is the number of FFT points; (12) Initial phase modulation of the transmitted signal: K pulses are transmitted within each coherent accumulation phase of the radar. Assume the transmitted signal of the kth pulse is... Assume the transmitted signal is a linear frequency modulated signal: in Let f0 be a rectangular window function, where f0 is the carrier frequency of the transmitted signal; μ = B / τ represents the frequency modulation slope, B is the signal bandwidth, and τ is the signal duration; The modulated signal is obtained by adding initial phase modulation. : Finally, the signal Radiation is emitted from the m-th antenna element, and a total of K pulses are required for each coherent accumulation cycle; (20) Echo data preprocessing: For a subarray digital radar, after each digital channel receiver receives the echo data, it undergoes amplification, down-conversion, filtering, A / D conversion, and pulse compression to obtain K pulse echo signals within a coherent accumulation time. (30) Target coherent accumulation and beamforming: The prior phase information is used to compensate and coherently accumulate the K pulse echo signals. For the echo signal of the m-th antenna element, since the phase was correctly compensated before coherent accumulation, it is accumulated during the coherent accumulation process, while the echoes of the other antenna elements are suppressed as sidelobes during accumulation. Thus, the echo signal of the m-th antenna element is separated. The separated element signals are digitally beamformed and the spatial domain is set according to the system settings.

2. The digital implementation method of a phased array radar unit based on initial phase modulation according to claim 1, characterized in that, The echo data preprocessing step (20) includes: (21) Signal reception: Assuming the target distance from the radar is R0, the radar receives K pulses within one coherent accumulation time, where the echo of the kth pulse is... in The scattering coefficient of the target is represented by , and c represents the speed of light. (21) Amplify, downconvert, filter, and perform A / D operations on the signal: The echo signal of the kth pulse Superimposed signals from M antenna elements ,in This represents the echo received by the m-th antenna element from the k-th pulse. Represents other echoes and noise in space; After A / D conversion, the time-domain sampling matrix is ​​obtained, and the echo is represented as: Where N is the number of sampling points of the gate, K is the number of pulses in the coherent accumulation time, and r is included in the formula. k, n This represents the sampled value at the nth time point of the kth pulse. , ; (22) Pulse compression: A matching signal for a linear frequency modulated radar wave is generated according to the radar parameters. Each pulse echo is processed by pulse compression to obtain a pulse compression matrix signal. , in, This represents the pulse pressure result at the nth time point of the kth pulse.

3. The digital implementation method of a phased array radar unit based on initial phase modulation according to claim 2, characterized in that, The (30) target coherent accumulation and beamforming steps include: (31) Phase compensation: using random phase values Compensation is performed on the echoes of K pulses. When it is necessary to separate the signal of the m-th antenna element, the echo after pulse compression is... Random phase added by the upper compensation The echo of the m-th unit is obtained. Represented as: in The sampled values ​​of the k-th pulse and the n-th distance scale after phase compensation for the m-th unit are given. N is the number of sampling points of the gate, and K is the number of pulses in the coherent accumulation time; (32) Coherent accumulation: The echoes of K pulses from the same distance unit are weighted and superimposed to form a peak in the corresponding Doppler frequency channel; the input signal is the echo pulse train after phase compensation; the output signal of the same distance unit after coherent processing is: Where p represents the p-th Doppler channel. , This represents the sampled value of the p-th Doppler channel and the n-th distance scale of the m-th antenna element; (33) Beamforming: For different operating modes, operating frequencies, amplitude indices, and beam directions, the amplitude and phase weights of each digital channel are obtained from the index table, and multiple beams are formed to meet the needs of search, tracking, identification, and auxiliary beams under different operating modes; based on the existing channel weighting coefficients, the beamforming result is expressed as: in Represents the beamforming weighting coefficients. Represents the antenna elements participating in beamforming. , Configure according to system requirements.

4. The digital implementation method of a phased array radar unit based on initial phase modulation according to claim 1, characterized in that, initial phase The value is an integer. The optimal solution of the optimization function in step (11) is obtained through offline search.

5. The digital implementation method of a phased array radar unit based on initial phase modulation according to claim 3, characterized in that, In step (32), since the phase of the echo of the other antenna elements cannot be correctly compensated, it is distributed on the sidelobe during coherent accumulation, and is suppressed by windowing in the later stage.

6. A digital realization device for a phased array radar unit based on initial phase modulation, characterized in that, The device includes an initial phase modulation module, an echo data processing module, and a target phase coherence accumulation and digital beamforming module. The device realizes the unit digitization of the phased array radar according to the method of any one of claims 1-5.

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