A multi-frequency band fusion microwave photon radar based on a multi-channel electro-optic modulation chip

Abstract

The application discloses a multi-frequency-band fusion microwave photon radar based on a multi-channel electro-optic modulation chip, which comprises a silicon-based multi-channel external modulation chip, a multi-octave radar signal generation module and a multi-octave radar receiving module, the silicon-based multi-channel external modulation chip is divided into two double-driven intensity modulators, the multi-band radar signal generated on the uplink double-driven intensity modulator is divided into two parts through an electrical power divider: one part is transmitted to the free space through an ultra-wideband antenna after being amplified by a photoelectric detector, so that radar detection is realized, and the other part is received by the downlink double-driven intensity modulator as a radar dechirp reference signal and a multi-band echo signal, the radar dechirp reference signal and the multi-band echo signal are mixed by a low-speed photoelectric detector, so that photon dechirp processing is realized, and the photon dechirp processing is sent to a real-time radar multi-subband synthesis digital processing module for coherent fusion, and the multi-band radar is realized to complete ranging and imaging in real time through an inverse synthetic aperture imaging algorithm. The application has the advantages of low cost, easy realization, high imaging resolution, small system complexity and the like.

Description

Technical Field

[0001] This invention pertains to multi-band radar processing technology, and relates to microwave photonics, photonic integration technology, large signal modulation technology, multi-octave band and multi-band radar technology, multi-subband coherent synthesis technology, radar imaging technology, etc., and particularly relates to a multi-band fusion microwave photonic radar based on a multi-channel electro-optic modulation chip. Background Technology

[0002] Radar acquires information, such as the distance, angle, and speed of a target, through the transmission and reception of electromagnetic waves. Its detection function plays a vital role in military, weather forecasting, and resource exploration applications. To achieve high-precision target positioning and high-resolution capabilities, wide-bandwidth radar signals are essential. However, using traditional electronic components to process wide-bandwidth radar signals has the following drawbacks: (1) The local oscillator clock frequency of traditional electronic components is only a few GHz, which limits the generation of wide-bandwidth radar signals; (2) The up-conversion and down-conversion operations introduce additional complexity to the system; (3) Ultra-high-speed digital-to-analog converters are required to generate wide-bandwidth analog signals, which will place a heavy burden on the system.

[0003] The emergence of microwave photonics technology has broken through the bottlenecks of traditional electronic technology, bringing new solutions to this problem. Leveraging the advantages of microwave photonics, such as its large bandwidth, low loss, and resistance to electronic interference, ultra-wideband radar (several GHz and above) can achieve centimeter-level or even sub-centimeter-level ultra-high resolution, greatly improving radar performance. Currently, photonics-assisted radar systems are mainly single-band; for example, a 18-26 GHz single-band radar system was generated using photonics-based frequency quadruple harmonics ("Photonics-based broadband radar for high resolution and real-time inverse synthetic aperture imaging", Optics Express, pp. 16274-16281, 2017). However, for the complex electronic / electromagnetic spectrum battlefields of the future, with their wide spectrum coverage and complex electromagnetic interference, single-band radar can no longer meet military requirements. Furthermore, the proposed multi-band photonic radar systems use discrete, complex, and redundant photonic devices, with each band using a separate radar signal generation and processing system, which will significantly increase the cost of military equipment. Summary of the Invention

[0004] The present invention aims to provide a radar device with advantages such as low cost, ease of implementation, and high imaging resolution. To achieve the above objective, the present invention provides a multi-band fusion microwave photonic radar based on a multi-channel electro-optic modulation chip.

[0005] This invention discloses a multi-band fusion microwave photonic radar based on a multi-channel electro-optic modulation chip, comprising a laser, a silicon-based multi-channel external modulation chip, a multi-octave radar signal generation module, and a multi-octave radar receiving module. The silicon-based multi-channel external modulation chip integrates the generation and reception of multi-octave multi-band radar signals. Specifically, the laser generates a continuous optical carrier and injects it into the silicon-based multi-channel external modulation chip, which integrates four phase modulators, combined into upper and lower dual-drive intensity modulators according to their transmit / receive functions. The upper dual-drive intensity modulator serves as the main unit in the transmission process. An intermediate frequency narrowband linear frequency modulated signal is applied to the upper dual-drive intensity modulator under large-signal modulation to generate higher-order optical sidebands. Subsequently, a photodetector is used to generate multi-octave multi-band radar signals, whose center frequencies and bandwidths are multiples of each other. A power divider splits the multi-band radar signal into two parts: one part is amplified by a power amplifier and transmitted into free space through an ultra-wideband antenna, simultaneously enabling multi-band radar detection and imaging; the other part serves as a multi-band reference signal for radar demodulation and dechirping. During reception, a dual-drive intensity modulator acts as the main unit. The multi-band echo signal reflected from the target object is acquired by the ultra-wideband receiving antenna, amplified by a low-noise amplifier, and simultaneously applied to the dual-drive intensity modulator along with the multi-band reference signal. After mixing at a low-speed photodetector, photon dechirping of the multi-band radar signal is achieved, resulting in a low-frequency dechirped signal with multiple octave bands. A multi-subband coherent synthesis digital processing module performs coherent fusion of the low-frequency dechirped signal across multiple bands, and combined with an inverse synthetic aperture radar (ISAR) imaging algorithm, real-time ranging and imaging of the multi-band radar are achieved.

[0006] Furthermore, the multi-band radar dechirped signal generated by single-channel radar reception and processing still maintains multiple harmonics, with its center frequency being a multiple of the signal.

[0007] Furthermore, the multi-octave radar signals generated under large-signal modulation have spectral gaps between their frequency bands. By using radar multi-subband coherent synthesis processing technology to fit the multi-octave full-pole model, the missing frequency bands are filled, thereby synthesizing an equivalent ultra-wide bandwidth radar signal covering multiple frequency bands and improving the range resolution of the radar system.

[0008] The beneficial technical effects of this invention compared to the prior art are as follows:

[0009] This invention utilizes a silicon-based multi-channel external modulator to simultaneously generate and receive multi-octave band signals, and employs a radar multi-subband coherent synthesis algorithm to achieve equivalent large-bandwidth radar detection. Compared to traditional large-bandwidth radar detection systems, it offers advantages such as low cost, low system complexity, and high robustness. Only a low-speed waveform generator is needed to generate a mid-frequency narrowband linear frequency modulated signal. Multi-octave band, multi-band radar signals can be generated through large-signal modulation and the silicon-based multi-channel external modulator. Finally, the multi-subband coherent synthesis processing algorithm obtains the equivalent large-bandwidth radar signal and completes ultra-wideband radar detection. Attached Figure Description

[0010] Figure 1 This is a block diagram of the multi-band fusion microwave photonic radar system based on a multi-channel electro-optic modulation chip according to the present invention.

[0011] Figure 2 This is a block diagram of the radar multi-subband coherent synthesis digital processing module of the present invention.

[0012] Figure 3 A schematic diagram of multi-band, multi-octave band signals generated with photonics assistance.

[0013] Figure 4 This is a schematic diagram of coherent synthesis processing of multioctave band signals. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0015] This invention provides a multi-band fusion microwave photonic radar based on a multi-channel electro-optic modulation chip, such as... Figure 1 As shown, the system includes a laser 10, a silicon-based multi-channel external modulation chip 20, a multi-octave band radar signal generation module 30, and a multi-octave band radar receiving module 40. Dashed lines represent electrical paths, and solid lines represent optical paths. The silicon-based multi-channel external modulation chip 20 integrates multi-octave band multi-band radar signal generation and reception. The specific process is as follows:

[0016] Laser 10 generates a continuous optical carrier wave which is injected into a silicon-based multichannel external modulation chip 20. The silicon-based multichannel external modulation chip 20 integrates four phase modulators, which are combined into upper and lower dual-drive intensity modulators according to their transmit / receive functions. The upper dual-drive intensity modulator serves as the main unit of the transmission process. An intermediate frequency narrowband linear frequency modulated signal is applied to the upper dual-drive intensity modulator under large-signal modulation to generate higher-order optical sidebands. For example... Figure 3 As shown in A, the generated center frequency is f c A mid-frequency narrowband linear frequency modulated signal with bandwidth Bw in a large-signal modulation state (e.g.) Figure 3Under condition B), higher harmonics appear. The first harmonic is the original signal, and the second, third, fourth, ... Nth harmonics are new signals generated under the modulation of a large signal (such as...). Figure 3 The signal (C) spans multiple bands. The optical signal output from the upper dual-drive intensity modulator is then injected into the photodetector 301 to generate a multi-octave multi-band radar signal. A power divider 302 splits the multi-band radar signal into two parts: one part is amplified by a power amplifier 303 and transmitted into free space through an ultra-wideband antenna 304, simultaneously achieving multi-band radar detection and imaging; the other part serves as a multi-band reference signal for radar demodulation and dechirping. During reception, the lower dual-drive intensity modulator acts as the main unit. The multi-band echo signal reflected from the target object is collected by the ultra-wideband receiving antenna 401, and the free-space loss of the signal is compensated by a low-noise amplifier 402. This signal, along with the multi-band reference signal, is simultaneously applied to the lower dual-drive intensity modulator. Then, it is beat-frequency transmitted through a low-speed photodetector 403. The high-frequency portion is filtered out because it exceeds the device's operating frequency range, leaving only the dechirped signals of the radar's various harmonics, resulting in a multi-octave low-frequency dechirped signal. A multi-subband coherent synthesis digital processing module 404 is used to perform multi-band data fusion processing on the low-frequency dechirped signal. For example... Figure 4 As shown in Figure A, taking a four-band signal as an example, the four center frequencies and bandwidths are f0 and f1 respectively. c and Bw, 2f c and 2Bw, 3f c and 3Bw, 4f c And 4Bw multi-band signals, their time-domain waveforms are as follows Figure 4 As shown in C, multi-octave dechirped signals (such as...) Figure 2 After being acquired by an oscilloscope, the data are passed through digital bandpass filters with the same center frequency and bandwidth as each sub-band to filter out each harmonic. After radar multi-sub-band coherent combining processing, the data from all sub-bands are integrated together. The bandwidth gaps are estimated using an all-pole model, resulting in an equivalent bandwidth of 3f. c +4Bw ultrawideband signal (e.g.) Figure 4 B), its time-domain waveform is as follows Figure 4 As shown in D, by adjusting the center frequency of the generated narrowband signal, it is possible to achieve synthetic signals with different bandwidths, thereby obtaining super-resolution real-time radar detection images.

[0017] In summary, this invention has the following features: 1) It integrates the generation and reception of multi-octave radar signals using only a single silicon-based integrated multi-channel external modulation chip; 2) After the narrowband linear frequency modulated signal is modulated by a large signal, a single silicon-based integrated optical modulation module can obtain multi-octave multi-band radar signals in the optical domain, eliminating the need for expensive high-speed waveform generators; 3) Unlike traditional multi-channel schemes that receive signals from each sub-band separately, this invention processes the chirped signal using a silicon-based chip and a single-channel module without changing its center frequency and bandwidth, resulting in a simple system structure; 4) It utilizes a real-time radar multi-sub-band coherent synthesis digital processing module to convert discontinuous sub-band signals in the frequency domain into coherent signals by adjusting amplitude / phase, fits each sub-band with a full-pole model and fills in the missing frequency bands, achieving high-resolution performance of ultra-wideband radar signals.

Claims

1. A multi-band fusion microwave photonic radar based on a multi-channel electro-optic modulation chip, characterized in that, The system includes a laser (10), a silicon-based multi-channel external modulation chip (20), a multi-octave radar signal generation module (30), and a multi-octave radar receiving module (40). The silicon-based multi-channel external modulation chip (20) integrates the generation and reception of multi-octave multi-band radar signals. Specifically, the laser (10) generates a continuous optical carrier and injects it into the silicon-based multi-channel external modulation chip (20). The silicon-based multi-channel external modulation chip (20) integrates four phase modulators, which are combined into upper and lower dual-drive intensity modulators according to their transmission and reception functions. The upper dual-drive intensity modulator serves as the main unit of the transmission process. A mid-frequency narrowband linear frequency modulated signal is applied to the upper dual-drive intensity modulator under large-signal modulation to generate high-order optical sidebands. Subsequently, a photodetector (301) is used to generate multi-octave multi-band radar signals. The center frequencies and bandwidths of the radar signals are multiples of each other. The multi-band radar signal is divided into two parts by a power divider (302): one part is amplified by a power amplifier (303) and transmitted to free space through an ultra-wideband antenna (304), thus realizing the detection and imaging of the multi-band radar. The other part is used as a multi-band reference signal for radar demodulation and dechirping. During the reception process, the lower dual-drive intensity modulator is the main unit. The multi-band echo signal reflected by the target object is collected by the ultra-wideband receiving antenna (401), amplified by a low-noise amplifier (402), and applied to the lower dual-drive intensity modulator at the same time as the multi-band reference signal. After the two are mixed by a low-speed photodetector (403), the photon dechirping of the multi-band radar signal is realized, resulting in a low-frequency dechirped signal with multiple octaves. A multi-subband coherent synthesis digital processing module (404) is used to coherently fuse low-frequency dechirped signals across multiple bands, and combined with an inverse synthetic aperture radar imaging algorithm, to complete the ranging and imaging of multi-band radar in real time.

2. The multi-frequency band fusion microwave photonic radar based on a multi-channel electro-optical modulation chip according to claim 1, characterized in that, The multi-band radar dechirped signal generated by single-channel radar reception and processing still retains multiple harmonics, with its center frequency being a multiple of the signal.

3. The multi-frequency band fusion microwave photonic radar based on multi-channel electro-optic modulation chip according to claim 1, characterized in that, The multi-octave radar signal generated under the large signal modulation has spectral gaps between its frequency bands. By using radar multi-subband coherent synthesis processing technology to fit the multi-octave full-pole model, the missing frequency bands are filled, thereby synthesizing an equivalent ultra-large bandwidth radar signal covering multiple frequency bands and improving the range resolution of the radar system.

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