A method, medium, and device for designing orthogonal waveforms for a distributed millimeter wave radar network

Abstract

The application provides a distributed millimeter wave radar network-oriented orthogonal waveform design method, medium and equipment, and belongs to the field of radar signal processing. By linearly increasing the starting frequency of each linear frequency modulation signal in each coherent processing interval, a large bandwidth is synthesized in the slow time domain, thereby generating a step double frequency modulation waveform with a variable center frequency. Based on the waveform, DDM coding with different Doppler band numbers is implemented in each radar unit, and FDM coding is implemented for coordination between radar units. Finally, MIMO waveform design for simultaneous orthogonal transmission of multiple transmitting antennas is completed, and complete separation is achieved through a range-Doppler spectrum. The application is flexible and suitable for different types of distributed millimeter wave radar networks and MIMO structures, effectively overcomes the limitations of low range resolution and small range-Doppler unambiguous range in existing methods, and greatly improves the MIMO coding effect, multi-target unambiguous detection and parameter estimation performance of the distributed millimeter wave radar network.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing, specifically relating to an orthogonal waveform design method, medium, and device for distributed millimeter-wave radar networks. Background Technology

[0002] As radar detection systems evolve towards networking and intelligence, distributed millimeter-wave radar networks, with their high angular resolution, multi-view collaborative sensing capabilities, and strong anti-interference characteristics, are gradually becoming an important development direction for next-generation radar technology. As a core component, multiple-input multiple-output (MIMO) radar achieves spatial virtual aperture expansion through orthogonal waveform diversity technology, significantly improving target detection and parameter estimation performance. However, in distributed millimeter-wave radar networks, the design of orthogonal waveforms among multiple transmitter units faces severe challenges: on the one hand, traditional orthogonal waveforms (such as linear frequency-modulated signals based on frequency division multiplexing (FDM) and time division multiplexing (TDM)) are limited by finite bandwidth allocation and Doppler tolerance, making it difficult to simultaneously achieve high range resolution and a large unambiguous Doppler range; on the other hand, as the network scale expands, the contradiction between the orthogonality dimension of the waveform and the number of channels becomes increasingly prominent, leading to intensified range-Doppler coupling effects in multi-target scenarios and significant parameter estimation ambiguity. Furthermore, existing methods are mostly designed for centralized MIMO architectures, making it difficult to adapt to the complex requirements of heterogeneous unit collaboration and dynamic topology changes in distributed networks, severely restricting the realization of the potential of the millimeter-wave band.

[0003] Against this backdrop, researching orthogonal waveform design methods for distributed millimeter-wave radar networks has urgent theoretical and engineering significance. It is imperative to overcome the trade-offs between range resolution and Doppler tolerance in existing technologies through innovation in waveform structure and coding mechanisms, while simultaneously improving the flexibility of waveform design and network adaptability. This will provide key technical support for distributed radar networks to achieve high-precision, unambiguous multi-target detection. Summary of the Invention

[0004] This invention addresses the problems of low range resolution, limited range-Doppler ambiguity range, and parameter estimation ambiguity caused by insufficient waveform orthogonality dimension when the network scales up in traditional orthogonal waveform design for distributed millimeter-wave radar networks. It provides an orthogonal waveform design method, medium, and device for distributed millimeter-wave radar networks. While ensuring orthogonal waveform performance, it has low computational complexity and is suitable for the real-time processing requirements of heterogeneous hardware units in distributed millimeter-wave radar networks. It provides an efficient solution for high-precision, ambiguity-free detection and parameter estimation of multiple targets in complex environments.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides an orthogonal waveform design method for distributed millimeter-wave radar networks, comprising the following steps:

[0007] S1: By linearly increasing the starting frequency of each linear frequency modulated signal within each coherent processing interval, a larger bandwidth is synthesized by frequency modulation in the slow time domain, thereby generating a stepped double frequency modulated waveform with a variable center frequency.

[0008] S2: Inside the transmitter of each MIMO radar unit, Doppler frequency shifts of different frequency bands are implemented in the slow time domain to perform DDM coding;

[0009] S3: In a distributed millimeter-wave radar network, a fixed frequency shift is applied to all transmitters of each radar unit in the fast time domain for FDM coding.

[0010] S4: By superimposing DDM and FDM hybrid coding on the stepped dual frequency modulation waveform, the MIMO waveform design for simultaneous orthogonal transmission by multiple transmitting antennas is completed.

[0011] Optionally, in step S1, the frequency modulation slope is γ and the pulse repetition period is T. c Based on the linear frequency modulation waveform, in each T c The sampling frequency f s Collect N r For each sample, by linearly increasing the starting frequency of each linearly modulated signal within each coherent processing interval, a larger bandwidth is synthesized in the slow time domain using frequency modulation: B syn =κ(N) d -1)T c κ represents the slope of the starting frequency within the coherent processing interval, and N d The number of linear frequency modulated signals transmitted within each coherent processing interval; for the nth interval... d A linear frequency modulated signal has a sampling start frequency of f′. c =f c +κ(n d -1)T c For a target at a distance of R and a velocity of v, the discrete form of the beat frequency signal y of the generated step double-frequency modulated waveform with a variable center frequency is... BB [n r n d ] is represented as:

[0012]

[0013] In the formula, f c Where is the carrier frequency of the radar system, c is the speed of light, and T is the speed of light. s It is the sampling period, T s =1 / f s nr =1,2,...,N r and n d =1,2,...,N d These represent the sequence indices of the pulse sampled and linear frequency modulated signals, respectively.

[0014] Optionally, in step S2, for the internal existence of M t For each transmitter's radar element, the following DDM code is selected for the slow time domain:

[0015] P m =[1, exp(j2π(m-1) / N),..., exp(j2π(m-1)(Nd-1) / N)], N≥M t ;

[0016] In the formula, P m This indicates DDM coding, where N represents the number of Doppler virtual bands, and m represents the transmit antenna number, m = 1, 2, ..., M. t .

[0017] Optionally, in step S2, the transmitter signals within each radar unit are orthogonal in the slow time domain.

[0018] Optionally, in step S2, the number N of Doppler virtual frequency bands for each radar unit is different.

[0019] Optionally, in step S3, there exists M d There are n radar elements, and the carrier frequency of the nth radar element has a frequency offset from the reference frequency. Different radar units were selected sequentially, and the fast-time signals of all their transmitters were encoded using the following FDM code:

[0020]

[0021] In the formula, P n Indicates FDM encoding, T s It is the sampling period, T s =1 / f s In each pulse repetition period T c The sampling frequency f s Collect N r One sample.

[0022] Optionally, in step S3, the frequency offset set of multiple radar elements The tolerance is not f s / M d Arithmetic sequence:

[0023]

[0024] In the formula,

[0025] Optionally, in step S4, for a MIMO waveform where multiple transmitting antennas transmit orthogonally simultaneously, the discrete form of the beat frequency signal received by the q-th radar element from the m-th transmitter of the n-th radar element is... Represented as:

[0026]

[0027] In the formula, and These represent the frequency offsets between the carrier frequency and the reference frequency of the nth and qth radar elements, respectively; N represents the number of Doppler virtual bands.

[0028] For all transmitted signals received by the q-th radar unit, a range-Doppler spectrum is generated using a two-dimensional Fourier transform:

[0029]

[0030] In the formula, Y q [f r f d ] represents the distance Doppler spectrum, indicating the existence of M. d There are one radar unit, and M exists inside each radar unit. t One transmitter, yes The two-dimensional Fourier transform is performed to obtain f. r and f d Y represents the distance frequency axis and the Doppler frequency axis, respectively. BB [f r f d [This represents the RD diagram of the original step-double frequency modulated signal.] The frequency of the DDM code after Fourier transform is represented; the distance-Doppler spectrum is used to separate the multi-channel signals.

[0031] In a second aspect, the present invention provides a computer-readable storage medium storing a computer program that causes a computer to execute the orthogonal waveform design method for distributed millimeter-wave radar networks as described in the first aspect.

[0032] Thirdly, the present invention provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the orthogonal waveform design method for distributed millimeter-wave radar networks as described in the first aspect.

[0033] The beneficial effects of this invention are:

[0034] (1) This invention synthesizes a large bandwidth through slow time-domain frequency modulation, which effectively improves the maximum Doppler ambiguity range and the maximum range ambiguity range while ensuring the high range resolution of millimeter-wave radar networks. Specifically, compared with the single DDM method, the maximum Doppler ambiguity range is increased by M d The maximum distance ambiguity range is increased by M times compared to the single FDM method. t times.

[0035] (2) The present invention adopts a hybrid mechanism of intra-unit Doppler diversity (DDM) coding and inter-unit frequency division multiplexing (FDM) coding to dynamically allocate the orthogonal dimension of the waveform in the distributed network. This not only supports the collaborative work of heterogeneous radar units (such as different numbers of antennas or hardware capabilities) but also adapts to the dynamic changes in network topology, overcoming the limitations of rigid waveform design in traditional centralized MIMO. Attached Figure Description

[0036] Figure 1 A flowchart of an orthogonal waveform design method for distributed millimeter-wave radar networks;

[0037] Figure 2 A schematic diagram of a stepped double frequency modulation waveform with a variable center frequency;

[0038] Figure 3 This is a schematic diagram of a distributed millimeter-wave radar network.

[0039] Figure 4 This is a schematic diagram of the FDM-DDM hybrid encoding waveform;

[0040] Figure 5 A schematic diagram of the beat frequency signal range Doppler for each radar unit. Detailed Implementation

[0041] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0042] In one embodiment, the present invention proposes an orthogonal waveform design method for distributed millimeter-wave radar networks. For example... Figure 1 As shown, the method includes the following steps:

[0043] S1: By linearly increasing the starting frequency of each linear frequency modulated signal within each coherent processing interval, a larger bandwidth is synthesized in the slow time domain, thereby generating a stepped double frequency modulated waveform with a variable center frequency.

[0044] In this embodiment, the frequency modulation slope is γ and the pulse repetition period is T. c Based on the traditional linear frequency modulation waveform, in each T c The sampling frequency f s Collect N rEach sample, by linearly increasing the starting frequency of each linearly modulated signal within the coherent processing interval, expands the synthesized bandwidth. For this specific configuration, the synthesized bandwidth can be expressed as: B syn =κ(N) d -1)T c κ represents the slope of the starting frequency within the coherent processing interval, and N d The number of linear frequency modulated signals transmitted within each coherent processing interval, and the stepped double frequency modulated waveform with a variable center frequency, as shown below. Figure 2 As shown. Then, for the nth... d For a linear frequency modulated signal, the sampling start frequency is calculated as: f′ c =f c +κ(n d -1)T c For a target at a distance of R and a velocity of v, the discrete form of the beat frequency signal of a stepped double-frequency modulated waveform with a variable center frequency can be expressed as:

[0045]

[0046] Among them, f c Where is the carrier frequency of the radar system, c is the speed of light, and T is the speed of light. s It is the sampling period, T s =1 / f s n r =1,2,...,N r and n d =1,2,...,N d These represent the sequence indices for pulse sampling (fast time) and linear frequency modulated signals (slow time), respectively.

[0047] S2: Implement Doppler frequency shifts of different frequency bands in the slow time domain inside the transmitter of each small MIMO radar unit, and perform DDM coding.

[0048] In this embodiment, it is assumed that there are M transmitters inside a specific radar unit. For each transmitter, the following DDM code is used in the slow time domain:

[0049] P m =[1,exp(j2π(m-1) / N),..., exp(j2π(m-1)(N d -1) / N)],N≥M t ;

[0050] Where N represents the number of Doppler virtual frequency bands, ensuring that the signals from each transmitter within each radar unit are orthogonal in the slow time domain, and m represents the transmitting antenna number, m = 1, 2, ..., M. tTo ensure that the Doppler frequency shifts of the signals from different transmitters in different radar units do not overlap, each radar unit needs to use a unique DDM code, meaning that the number of Doppler virtual frequency bands N is different.

[0051] S3: In a distributed millimeter-wave radar network, a fixed frequency shift is applied to all transmitters of each radar in the fast time domain for FDM coding.

[0052] In this embodiment, it is assumed that there exists M. d There are n radar elements, and the carrier frequency of the nth element is said to have a frequency offset from the reference frequency. Different radar units were selected sequentially, and the fast-time signals of all their transmitters were encoded using the following FDM code:

[0053]

[0054] To ensure that target signals received simultaneously from multiple radars do not overlap in range-frequency shift, a frequency offset set is required. The tolerance is not f s / M d An arithmetic sequence, namely:

[0055]

[0056] Without losing generality,

[0057] S4: By superimposing DDM and FDM hybrid coding on the stepped dual frequency modulation waveform, the MIMO waveform design for simultaneous orthogonal transmission by multiple transmitting antennas is completed.

[0058] In this embodiment, DDM and FDM hybrid coding are superimposed on the stepped dual-frequency modulation waveform to complete the MIMO waveform design for simultaneous orthogonal transmission by multiple transmitting antennas. Therefore, the discrete form of the beat frequency signal received by the q-th radar unit from the m-th transmitter of the n-th radar unit can be expressed as:

[0059]

[0060] in, Then, for all transmitted signals received by the q-th radar, a range-Doppler spectrum is generated using a two-dimensional Fourier transform:

[0061]

[0062] in, yes The two-dimensional Fourier transform is performed to obtain f. r and f d Y represents the distance frequency axis and the Doppler frequency axis, respectively. BB [fr f d [This represents the RD diagram of the original step-double frequency modulated signal.] This represents the frequency after the Fourier transform of the DDM code. Using the aforementioned range-Doppler spectrum, multiple signals can be distributed across different distances and Doppler subbands, achieving multi-channel signal separation.

[0063] Next, we will use test examples to illustrate the effectiveness of the method in this embodiment.

[0064] Figure 3 A distributed millimeter-wave radar network structure is demonstrated, which includes two independent radar units that are coherently cascaded through local oscillator and trigger signals to form a coherent radar system. Each radar is equipped with three transmitters and one receiver. Figure 4 This demonstrates a possible hybrid FDM-DDM distributed radar system configuration suitable for... Figure 3 The distributed millimeter-wave radar network shown uses DDM codes for radar 1 and radar 2 with different Doppler virtual frequency band numbers N=3 and N=4, respectively. The phase of each transmitter in each radar changes between pulses. The radar configuration parameters are set as follows: starting frequency 76 GHz, bandwidth 256 MHz, dual-frequency modulation synthesis bandwidth 768 MHz, ADC sampling rate 30 Msps, modulation period 20 μs, fast-time sampling points 128, slow-time sampling points 512, and so on. The value is 10 Msps, after the method proposed in this embodiment. Figure 4 After implementing the encoding strategy, the distance-Doppler spectra of the two receivers were obtained, as shown below. Figure 5 As shown in (a) and (b), it can be seen that the sub-band ranges of all target signals in the two spectra do not overlap, enabling the separation of multiple channel signals. Under the same experimental conditions as above, different dual-frequency modulation synthesis bandwidths of 512MHz, 768MHz, and 1024MHz were set to test various distributed millimeter-wave radar network test cases (different numbers of radar elements and different numbers of transmitters). The test results were compared with those of the traditional single modulation method. The experimental results are shown in Table 1. It can be seen that not only is the range resolution increased and the range Doppler unambiguity range increased, but channel separation is also successfully achieved. This demonstrates the effectiveness and correctness of the method in this embodiment for distributed millimeter-wave radar networks.

[0065] Table 1 shows the comparative test results between the proposed waveform orthogonal method and the traditional single modulation method.

[0066]

[0067] In another embodiment, the present invention provides a computer-readable storage medium storing a computer program that causes a computer to execute the orthogonal waveform design method for distributed millimeter-wave radar networks described in the foregoing embodiments.

[0068] In another embodiment, the present invention proposes an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the orthogonal waveform design method for distributed millimeter-wave radar networks described in the foregoing embodiment.

[0069] In the embodiments disclosed in this application, a computer storage medium may be a tangible medium that may contain or store programs for use by or in conjunction with an instruction execution system, apparatus, or device. The computer storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of computer storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0070] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0071] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An orthogonal waveform design method for distributed millimeter-wave radar networks, characterized in that, Includes the following steps: S1: By linearly increasing the starting frequency of each linear frequency modulated signal within each coherent processing interval, a larger bandwidth is synthesized by frequency modulation in the slow time domain, thereby generating a stepped double frequency modulated waveform with a variable center frequency. In step S1, when the frequency modulation slope is The pulse repetition period is Based on the linear frequency modulation waveform, in each Internal sampling frequency collection For each sample, by linearly increasing the starting frequency of each linearly frequency-modulated signal within each coherent processing interval, a larger bandwidth is synthesized in the slow time domain using frequency modulation: , This represents the slope of the starting frequency within the coherent processing interval. The number of linear frequency modulated signals transmitted within each coherent processing interval; for the th A linear frequency modulated signal has a sampling start frequency of: For distance is Speed ​​is The goal is to generate a discrete form of the beat frequency signal of a stepped double-frequency modulated waveform with a variable center frequency. Represented as: ； In the formula, It is the carrier frequency of the radar system. It's the speed of light. It is the sampling period. , and These represent the sequence indices of the pulse-sampled and linearly frequency-modulated signals, respectively. S2: Inside the transmitter of each MIMO radar unit, Doppler frequency shifts of different frequency bands are implemented in the slow time domain to perform DDM coding; S3: In the distributed millimeter-wave radar network, a fixed frequency shift is applied to all transmitters of each MIMO radar unit in the fast time domain for FDM coding. S4: By superimposing DDM and FDM hybrid coding on the stepped dual frequency modulation waveform, the MIMO waveform design of simultaneous orthogonal transmission of multiple transmit antennas is completed; In step S4, for a MIMO waveform transmitted orthogonally by multiple transmitting antennas simultaneously, the discrete form of the beat frequency signal received by the q-th MIMO radar element from the m-th transmitter of the n-th MIMO radar element is... Represented as: ； In the formula, , and These represent the frequency offsets between the carrier frequency and the reference frequency of the nth and qth MIMO radar elements, respectively. Indicates the number of Doppler virtual bands; For all transmitted signals received by the q-th MIMO radar element, a range-Doppler spectrum is generated using a two-dimensional Fourier transform: ； In the formula, This indicates the distance to the Doppler spectrum, and there exists... Each MIMO radar unit contains a MIMO radar element, and the MIMO radar element contains... One transmitter, yes The result is obtained by performing a two-dimensional Fourier transform. and These represent the distance frequency axis and the Doppler frequency axis, respectively. The RD diagram represents the original signal of the step-double frequency modulation. The frequency of the DDM code after Fourier transform is represented; the distance-Doppler spectrum is used to separate the multi-channel signals.

2. The orthogonal waveform design method for distributed millimeter-wave radar networks as described in claim 1, characterized in that: In step S2, for those that exist internally For each transmitter's MIMO radar element, the following DDM code is selected for the slow time domain: ； In the formula, Indicates DDM encoding. Indicates the number of Doppler virtual frequency bands. Indicates the transmitting antenna number. .

3. The orthogonal waveform design method for distributed millimeter-wave radar networks as described in claim 2, characterized in that: In step S2, the transmitter signals within each MIMO radar unit are orthogonal in the slow time domain.

4. The orthogonal waveform design method for distributed millimeter-wave radar networks as described in claim 2, characterized in that: In step S2, the number of Doppler virtual frequency bands for each MIMO radar unit different.

5. The orthogonal waveform design method for distributed millimeter-wave radar networks as described in claim 1, characterized in that: In step S3, there exists There are n MIMO radar elements, and the carrier frequency of the nth MIMO radar element has a frequency offset from the reference frequency. Different MIMO radar units were selected sequentially, and the fast-time signals of all their transmitters were encoded using the following FDM code: ； In the formula, Indicates FDM encoding, It is the sampling period. In each pulse repetition cycle Internal sampling frequency collection One sample.

6. A computer-readable storage medium storing a computer program, characterized in that, The computer program causes the computer to execute the orthogonal waveform design method for distributed millimeter-wave radar networks as described in any one of claims 1-5.

7. An electronic device, characterized in that, include: The memory, the processor, and the computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the orthogonal waveform design method for distributed millimeter-wave radar networks as described in any one of claims 1-5.

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