Multi-channel parallel radar digital beamforming method and device based on optical analog-to-digital conversion

Abstract

A kind of multi-channel parallel radar digital beamforming method based on optical analog-digital conversion.Facing the bandwidth bottleneck problem of traditional electrical analog-digital converter and the problem of beamforming calculation data volume in radar digital beamforming, the method adopts optical analog-digital converter and parallel computing architecture, improves the bandwidth of analog-digital conversion through the broadband advantage of optical information processing, so that digital beamforming can process broadband high frequency electromagnetic signals; at the same time, based on the characteristics of multi-channel data parallel output of optical analog-digital conversion, the calculation process of digital beamforming is parallelized, so that the digital beamforming calculation can be completed by using the array of parallel computing units, the calculation data volume in each computing unit is reduced, the requirement of computing unit hardware resources, the process difficulty and process cost of hardware manufacturing are reduced, and further, the real-time performance of digital beamforming is improved by parallel computing method.

Description

Technical Field

[0001] This invention relates to radar systems based on optical information processing, specifically a multi-channel parallel radar digital beamforming method and apparatus based on optical analog-to-digital conversion. Background Technology

[0002] In modern radar systems, with the continuous widening of electromagnetic frequency bands, high-frequency broadband signals have become an important component of radar transmitted signals. However, due to the typically high transmission loss of high-frequency broadband signals along their spatial propagation paths, beamforming technology—which concentrates electromagnetic signal power to transmit and receive electromagnetic signals in the form of beams—has become one of the mainstream operating modes for radar. From a signal classification perspective, beamforming technology, as a signal processing method, can also be divided into two categories: analog beamforming and digital beamforming. The former, in the analog domain, uses methods such as electrical phase shifters, electrical link delays, and antenna array design to add different phase shifts to the signals received or transmitted by different antennas in the array. It has advantages such as high processing speed for a single beam direction, but its disadvantage lies in its limited flexibility; that is, it can only manage and generate one beam at a time and cannot simultaneously perform beamforming on multiple beam directions. The latter involves adding corresponding phase offsets to the signals of different antenna links by digitally calculating the digital signals after digital-to-analog conversion. Since the beamforming process is completed in the digital domain, digital beamforming technology has very high flexibility and can be used in radar detection scenarios that require simultaneous multi-beamforming. However, its disadvantage is that the performance of the radar largely depends on the performance of the analog-to-digital converter. The performance indicators of existing electrical analog-to-digital converters, such as bandwidth and sampling rate, are difficult to meet the requirements of high-frequency broadband radar systems. On the other hand, compared with analog beamforming technology, digital beamforming technology has a larger amount of data generation, and the increased computational load poses a major challenge to the real-time performance of the radar.

[0003] Optical analog-to-digital conversion (optical analog-to-digital conversion) technology utilizes the broadband advantage of light over electricity through optical information processing methods, enabling direct sampling of high-frequency broadband electromagnetic signals via high-speed optical pulses. In the optical domain, it transforms a high-speed single-channel sampling pulse sequence into multiple low-speed sampling pulse sequences, thereby alleviating the demands on the quantization rate and bandwidth of electrical analog-to-digital converters (ADCs). Ultimately, it achieves high-speed sampling of high-frequency, high-bandwidth signals on a low-speed, low-bandwidth ADC array. Therefore, using optical ADCs to construct digital radar receivers has the potential to solve the bottleneck problem of high ADC performance requirements in digital beamforming. On the other hand, while existing optical ADC systems have various architectures with their own characteristics and advantages, they all retain the method of multi-channel parallel data output. For example, channel-interleaved optical analog-to-digital converters (AADCs) utilize multi-stage cascaded Mach-Zehnder modulators to convert high-speed sampling pulses into multiple low-speed sampling pulses via serial-to-parallel conversion, ensuring that all ultra-wideband signal processing occurs in the optical domain. Parallel sampling AADCs leverage the equivalence of multiple low-speed optical pulses with a single high-speed optical pulse, achieving high-speed sampling through strict control of the optical path length, reducing modulator cascading, thus lowering link loss and increasing the effective bit depth. Time-wavelength interleaved AADCs fully utilize the wavelength dimension of light, using dense wavelength division multiplexing (DWDM) to convert a single high-speed sampling pulse into multiple low-speed sampling pulses with different center wavelengths, similarly reducing link loss. When processing multi-channel data, existing methods always first integrate the parallel output data from multiple channels into single-channel sampled data, and then perform unified processing on the complete sampled data. This large-volume processing method struggles to meet the real-time requirements of digital beamforming calculations, and the significant increase in data volume further complicates the hardware resource configuration requirements of the computing unit, increasing manufacturing costs and complexity. Therefore, improving radar digital beamforming performance by utilizing optical analog-to-digital conversion requires not only improvements at the radar receiver level, but also improvements to the calculation methods and processes of digital beamforming based on the characteristics of the hardware itself. The feature of multi-channel parallel output provides room for improvement in processing speed and real-time performance for existing optical analog-to-digital conversion data processing methods. Summary of the Invention

[0004] The purpose of this invention is to introduce optical information processing methods into radar beamforming to improve the broadband high-frequency performance indicators achievable by digital beamforming. At the same time, in response to the problem of large data volume after introducing optical information processing methods, and combining the multi-channel characteristics of optical analog-to-digital conversion itself, a parallel computing process for digital beamforming is given to realize digital beamforming function with real-time performance.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] On the one hand, the present invention provides a multi-channel parallel radar digital beamforming method based on optical analog-to-digital conversion data, characterized in that the method includes the following steps:

[0007] Step 1: Construct an array radar system. The radar array includes... There are M antennas, where M is the number of antenna array rows and N is the number of antenna arrays. Each radar transmitting antenna is connected to a transmit link and a receive link. Waveform generation is completed on the transmit link, and signal reception and digitization are completed using a multi-channel optical analog-to-digital converter (AADC) system on the receive link. After the receive link, the data from each AADC system is divided into L outputs. The i-th data from all AADCs is input into the corresponding i-th computing unit to complete the digital beamforming process, and then transmitted to the data center.

[0008] Step 2: Within a beam scanning time window, scan the beam direction for the angle combination (θ, φ), where θ is the angle between the beam direction and the x-axis of the reference coordinate system in the antenna array plane, and φ is the elevation angle between the beam direction and the antenna array plane. To scan the beam direction, first, transmit the electromagnetic signal through the transmit link. After transmission, obtain the digitized reception result of the electromagnetic signal through the receive link, and then transmit the corresponding channel data of the analog-to-digital converter to the computing unit as described in Step 1.

[0009] Step 3: In each computing unit, write the parallel computing logic required to complete digital beamforming. The specific process can be represented as follows:

[0010]

[0011] R represents the data matrix of the calculated output, and its form is as follows:

[0012]

[0013] Where k represents the k-th angle combination (θ) k φ k The corresponding subscript of ) indicates that t represents the amount of signal data received by a single channel within a beam scanning window.

[0014] θ i Represents the i-th angle combination (θ) i φ i The beamforming vector of ) has the following mathematical form:

[0015]

[0016] d represents the data matrix passed into the computation unit, and has the following expression:

[0017]

[0018] The data in the i-th row and j-th column is d i，j This represents the signal value received by the i-th antenna at the j-th moment.

[0019] Step 4: Transmit the data from the L computing units to the data center, and complete the parallel-to-serial conversion process in the data center to obtain the final digital beamforming results for the k beam directions.

[0020] The radio frequency bands of the electromagnetic signals mentioned include, but are not limited to, X-band, Ku-band, Ka-band, W-band, and millimeter-wave band.

[0021] The multi-channel optical analog-to-digital conversion system includes, but is not limited to, channel-interleaved optical analog-to-digital conversion systems, parallel sampling optical analog-to-digital conversion systems, and time-wavelength interleaved optical analog-to-digital conversion systems.

[0022] The digital beamforming includes receiver-side digital beamforming and transmitter-side digital beamforming.

[0023] The parallel computing unit includes, but is not limited to, computers, FPGAs, and multiplier chips.

[0024] On the other hand, the present invention also provides a multi-channel parallel radar digital beamforming device based on optical analog-to-digital conversion data, characterized in that it includes:

[0025] The parallel transmission link is used to perform power conditioning and up-conversion of the transmitted signal and transmit it to the antenna array module;

[0026] The antenna array module is connected to the transmit link and the receive link, respectively.

[0027] The parallel receiving link is used to complete the signal power gain and complete the signal acquisition in the optical analog-to-digital conversion system, and then transmits the acquired signal to the parallel computing unit module.

[0028] The parallel computing unit module is used to complete the parallel processing required for beamforming and transmit the processing results to the data center module.

[0029] The data center module is used to integrate and display the final beamforming results.

[0030] Since current digital radar systems typically employ a down-conversion link and electronic analog-to-digital converter (ADC) receiving architecture, and perform overall computation on all ADC data at the computing level, the method of this invention has the following advantages compared to these methods:

[0031] 1. The optical analog-to-digital converter's ability to directly acquire high-frequency, wide-bandwidth electromagnetic signals increases the types of electromagnetic signal bands and signal bandwidth received by the radar, thereby improving the flexibility of digital beamforming at the signal type level.

[0032] 2. Based on the multi-channel characteristics of optical analog-to-digital conversion, parallel computation of multi-channel data was achieved for digital beamforming function, which reduced data processing time and difficulty and improved real-time performance.

[0033] 3. Based on the multi-channel data parallel computing method, the method was implemented using hardware devices. Since the overall data is distributed in parallel to multiple computing units, the hardware resource configuration requirements of each computing unit are reduced, thereby reducing the difficulty and cost of hardware manufacturing. Attached Figure Description

[0034] Figure 1 (a) is a schematic diagram of the process of the present invention. Figure 1 (b) is a schematic diagram of the apparatus described in this method.

[0035] Figure 2 This is a schematic diagram of an embodiment of the present invention.

[0036] Figure 3 The above are comparison diagrams of digital beamforming results in embodiments of the present invention, wherein (a) is a time domain waveform diagram without digital beamforming, and (b) is a time domain waveform diagram after digital beamforming according to the transmission angle.

[0037] Figure 4 The above are comparative diagrams showing the impact of digital beamforming on radar detection performance in embodiments of the present invention, wherein (a) is the detection performance diagram without digital beamforming, and (b) is the detection performance diagram after digital beamforming is performed according to the transmission angle. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0039] Step 1: First, set up the environment in this embodiment, such as... Figure 2 As shown. In this embodiment, the antenna array size is... Each antenna's receiving link is connected to a development board containing an optical analog-to-digital converter (ADC) system chip. The ADC has four channels. The development board transmits the ADC chip's data to an FPGA array, which also has four FPGAs, matching the number of channels in the ADC. The FPGA arrays then perform calculations on the directly acquired data and transmit it to a data center for aggregation and display.

[0040] Step 2: Scan the angle combination (30°, 60°) within a time window (0, 5ms). During the (0, 2.5ms) time window, switch the antenna array to transmit mode. At this time, the transmit link transmits uplink electromagnetic signals to the antenna array, which are then transmitted outwards via the antenna. During the (2.5ms, 5ms) time window, switch the antenna array to receive mode. At this time, the receive link receives the downlink electromagnetic signals transmitted by the antenna array, and the signals are directly sampled via an optical analog-to-digital converter chip array. The sampled results are then transmitted to the parallel FPGA computing unit.

[0041] Step 3 involves parallelizing digital beamforming calculations within the FPGA array, where each FPGA calculates the corresponding channel data for all optical analog-to-digital conversions. In this embodiment, angle combinations (30°, 60°) and (40°, 50°) are selected as the digital beamforming angle vectors. After the calculations are complete, the results are transmitted to a backend computer, which acts as a data center for aggregation and display.

[0042] Step 4: Perform parallel-to-serial conversion on the computer to obtain the final digital beamforming result. The waveform diagram after digital beamforming at angles (30°, 60°) is shown below. Figure 3 As shown in (b), for comparison, the waveform without beamforming is as follows: Figure 3 As shown in (a), it can be seen that the waveform changes after digital beamforming, and electromagnetic signals in other directions are suppressed. To further demonstrate the technical effect of this method, the radar detection effect after digital beamforming is further displayed on a computer, as shown below. Figure 4 As shown in (b), for comparison, Figure 4 (a) shows the radar detection effect without digital beamforming, which shows that the digital beamforming rate filters out the impact of interference from other directions on the detection effect.

Claims

1. A multi-channel parallel radar digital beamforming method based on optical analog-to-digital conversion data, characterized in that, Includes the following steps: Step 1: Constructing the radar array system: The radar array consists of M×N antennas, where M is the number of antenna array rows and N is the number of antenna arrays. Each radar transmitting antenna is connected to the transmitting link and the receiving link. Waveform generation is completed on the transmitting link, and signal reception and digitization are completed on the receiving link using a multi-channel optical analog-to-digital converter system. After the receiving link, the data from each optical analog-to-digital converter will be divided into L outputs. The i-th data from all optical analog-to-digital converters will be input into the corresponding i-th computing unit. After completing the digital beamforming process, the data is transmitted to the data center. Step 2: Within a beam scanning time window, scan the beam direction of the angle combination (θ, φ), where θ is the angle between the beam direction and the x-axis of the reference coordinate system in the antenna array plane, and φ is the elevation angle between the beam direction and the antenna array plane. To scan the beam direction, first, complete the transmission of electromagnetic signals through the transmit link. After the transmission is completed, obtain the digital reception result of the electromagnetic signals through the receive link, and transmit the corresponding channel data of the analog-to-digital converter to the computing unit as in Step 1. Step 3: In each computing unit, write the parallel computing logic required to complete digital beamforming, as shown in the following formula: （2,1） R represents the data matrix of the calculated output, and its form is as follows: （2,2） Where k represents the k-th angle combination (θ) k φ k The corresponding subscript of ) indicates that t represents the amount of signal data received by a single channel within a beam scanning window; θ i Represents the i-th angle combination (θ) i φ i The beamforming vector of ) has the following mathematical form: （2,3） d represents the data matrix passed into the computation unit, and has the following expression: （2,4） Where, d i，j This represents the signal value received by the i-th antenna at the j-th moment; Step 4: Transmit the data from the L computing units to the data center, and complete the parallel-to-serial conversion process in the data center to finally obtain the digital beamforming results for the k beam directions.

2. A device for implementing multi-channel parallel radar digital beamforming based on optical analog-to-digital conversion data using the multi-channel parallel radar digital beamforming method based on optical analog-to-digital conversion data as described in claim 1, characterized in that, include: The parallel transmission link is used to perform power conditioning and up-conversion of the transmitted signal and transmit it to the antenna array module; The antenna array module is connected to the transmit link and the receive link, respectively; The parallel receiving link is used to complete the signal power gain and complete the signal acquisition in the optical analog-to-digital conversion system, and then transmits the acquired signal to the parallel computing unit module. The parallel computing unit module is used to complete the parallel processing flow required for beamforming and transmit the processing results to the data center module. The data center module is used to integrate and display the final beamforming results.

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