WO2017028335A1 - 全波段覆盖的超宽带全光雷达系统 - Google Patents

全波段覆盖的超宽带全光雷达系统 Download PDF

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WO2017028335A1
WO2017028335A1 PCT/CN2015/088463 CN2015088463W WO2017028335A1 WO 2017028335 A1 WO2017028335 A1 WO 2017028335A1 CN 2015088463 W CN2015088463 W CN 2015088463W WO 2017028335 A1 WO2017028335 A1 WO 2017028335A1
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optical
signal
module
band
array
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PCT/CN2015/088463
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English (en)
French (fr)
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邹卫文
张昊
张斯滕
陈建平
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上海交通大学
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Priority to EP15901539.5A priority Critical patent/EP3324211B1/en
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Priority to US15/833,992 priority patent/US10605921B2/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/03—Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/0209—Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
    • G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems

Definitions

  • the invention relates to the field of microwave photonics and radar, in particular to an ultra-wideband all-optical radar system with full-band coverage.
  • Multi-band radars can operate in different bands simultaneously or cross-gated, so the probability of finding a target is higher than that of a normal radar.
  • the signal transmitted by the multi-band wide-band radar contains many frequency components, so it can break through the absorbing effect of the narrow-band absorbing material and effectively improve the radar's anti-stealth detection capability.
  • Multi-band radar is beneficial to suppress and avoid the interference of enemy casting, and has a positive effect on improving resolution, reducing multipath loss and enhancing its own survival rate.
  • microwave/millimeter wave radars often use the following signal forms: short pulse signals, phase Coded signal and chirp signal.
  • the short-pulse signal requires a relatively high pulse and requires a very narrow pulse width, so the transmission and reception technology based on the short pulse signal is often difficult to implement.
  • the phase-encoded signal is loaded with phase information on successive carriers at a certain time interval.
  • the test accuracy and side-lobe are relatively high, but the implementation is difficult and is affected by the Doppler effect and its dynamic range.
  • chirp signals are widely used in high-precision ranging and radar detection.
  • the FM bandwidth determines the accuracy of the range and is ideal for microwave/millimeter wave radar systems.
  • the object of the present invention is to overcome the above deficiencies of the prior art and to provide an ultra-wideband all-optical radar system with full-band coverage.
  • the same low-jitter, wide-spectrum mode-locked laser is used to generate and receive UWB chirp signals to ensure high coherence and high accuracy of the transceiver system.
  • the signal transmitter utilizes the wide spectrum of the mode-locked laser and the unbalanced dispersion ⁇ on both arms to achieve continuous adjustment of the center frequency, bandwidth and time width of the ultra-wideband signal for full-band coverage or any operating band.
  • the UWB radar signal is generated.
  • the signal receiver uses a time-stretching technique based on mode-locked lasers to compress the center frequency and bandwidth of the wideband signal, greatly reducing the pressure of the back-end analog-to-digital conversion and processing.
  • the distance resolution of the target detection remains accurate before time stretching. .
  • An ultra-wideband all-optical radar system with full-band coverage characterized in that it comprises a signal transmitter, a transceiver module and a signal receiver;
  • the signal transmitter comprises a mode-locked laser, a first dispersion module, and a first optical coupling , a second optical coupler, a first optical filter, a second dispersion module, a second optical filter, a first adjustable delay module, a third optical coupler, an optical amplifier, and a first photodetector;
  • the transceiver module includes a band selection switch, a first electrical amplifier array, a T/R component array, an antenna array, and a second electrical amplifier array;
  • the signal receiver includes a third optical filter, a second adjustable delay module,
  • the electro-optic modulator, the third dispersion module, the second photodetector, the analog-to-digital conversion module, and the signal processing module, the positional relationship of each of the above components is as follows:
  • the output of the mode-locked laser is connected to the input end of the first optical coupler via a first dispersion module, and the first optical coupler is divided into a first output end and a second output end: the first optical coupler
  • the first output end is connected to the input end of the second optical coupler
  • the second optical coupler divides the optical path into a first optical path and a second optical path, where the first optical path is a first optical filter and a second The dispersion module to the input end of the third optocoupler
  • the second optical path is in turn a second optical filter, an input of the first adjustable delay module to the third optical coupler, and the third optical coupler couples the signals of the first optical path and the second optical path to Outputting the optical amplifier together into the first photodetector, the first photodetector converting the optical signal into an electrical signal input to an input port of the band selection switch of the transceiver module, wherein the band selection switch has two or more An output port, each output port sequentially connecting a first electric amplifier array
  • optical signal of the second output end of the first optical coupler is sequentially input to the optical input end of the electro-optic modulator through the third optical filter and the second adjustable delay module to form an optical pulse carrier;
  • the electro-optic modulator loads the target echo electrical signal onto the optical pulse carrier to form an echo modulated optical signal corresponding to the target echo electrical signal, the electro-optic modulation
  • the echo modulated optical signal output by the device sequentially passes through the third dispersion module, the second photodetector, and the analog-to-digital conversion module to enter the signal processing module.
  • the mode-locked laser is a low-jitter, wide-spectrum mode-locked laser.
  • the filtering bandwidth of the third optical filter is greater than the filtering bandwidth of the first optical filter and the second optical filter.
  • the principle of the generation of the wideband chirp signal is based on spectral filtering and unbalanced dispersion ⁇ (see H. Zhang, W. Zou, and J. Chen, "Generation of widely tunable linearly-chirpedmicrowave”. Waveform based on spectral filtering and unbalanced dispersion, "Optics Letters, vol. 40, no. 6, pp. 1085-1088, 2015).
  • the center frequency and the sweep bandwidth of the generated wideband chirp signal are varied by adjusting the center wavelength and the filtering bandwidth of the first tunable optical filter and the second tunable optical filter.
  • the signal output by the transceiver module is converted by electro-optic, and the principle of time stretching is used (see Y. Han and B. Jalali, Photonic time-stretched analog-to-digital converter: Fundamental concepts and practical considerations). , Journal of Lightwave Technology, vol. 21, no. 12, pp. 3085-3103, 2003) Implements bandwidth compression and down conversion.
  • the radar echo signal is loaded onto the pre-dispersive optical pulse carrier by an electro-optic modulator to form a modulated optical signal corresponding to the radar echo signal.
  • the filtering bandwidth of the third optical filter needs to be larger than the filtering bandwidth of the first optical filter and the second optical filter, and then the second adjustable delay module is appropriately adjusted, so that echoes of multiple targets can be loaded onto the optical carrier. .
  • An electrical signal that is stretched several times in time is obtained by the second photodetector through a third dispersion module having a larger amount of dispersion. If the dispersion coefficients of the first dispersion module and the third dispersion module are D 1 and D 3 , respectively, the stretching multiple M will be determined by their ratio:
  • the RF signal to be sampled is stretched in time, equivalent to being compressed in the frequency domain, thereby greatly reducing the bandwidth of the back-end analog-to-digital conversion module and the sampling rate.
  • the analog-to-digital converted signal extracts useful target information through digital signal processing, and the distance resolution of the target detection still maintains the accuracy before time stretching.
  • the signal transmitter and signal receiver of the present invention are based on the same mode-locked laser, ensuring a high degree of coherence in signal generation and processing, thereby greatly improving the measurement accuracy of the present invention.
  • the present invention can generate a full-band coverage or an ultra-wideband chirp signal of either band by adjusting the first optical filter and the second optical filter.
  • the signal receiver of the present invention utilizes a time stretching technique to stretch the signal to be sampled in time and compress it in the frequency domain, thereby greatly reducing the bandwidth of the back-end analog-to-digital conversion module and the sampling rate.
  • the full-band coverage or different-band radar signals of the present invention adopt switchable transceiver channels to realize integrated transmission and reception of full-band coverage.
  • the target detection resolution of the present invention is determined by the bandwidth of the ultra-wideband radar signal generated by the transmitter, independent of the time stretch factor.
  • FIG. 1 is a schematic structural view of a full-band coverage ultra-wideband all-optical radar system according to the present invention.
  • FIG. 2 is a schematic structural view of a transceiver module.
  • Figure 3 shows the test results of the resulting UWB-covered UWB LFM signal characteristics.
  • Figure 4 shows the test results of the short-time Fourier transform analysis of the generated chirp signals of different bands.
  • FIG. 5 is an experimental diagram of single target detection and dual target detection using the generated X-band signal as an example. (a) single goal, (b) dual goal.
  • Fig. 6 is a test result of the time domain waveform of the X-band chirp signal before and after the time stretching and the short-time Fourier transform analysis in the single target detection.
  • Figure 7 shows the test results for different target spacings in dual target detection.
  • (d) when the distance is ⁇ 15.0 cm, the positions of the two targets after the filtering process are matched.
  • a full-band coverage ultra-wideband all-optical radar system includes a signal transmitter 1, a transceiver module 2, and a signal receiver 3. .
  • the signal transmitter 1 includes a mode-locked laser 1-1, a first dispersion module 1-2, a first optical coupler 1-3, a second optical coupler 1-4, a first optical filter 1-5, Second dispersion module 1-6, second optical filter 1-7, first adjustable delay module 1-8, third optical coupler 1-9, optical amplifier 1-10, first photodetector 1 11;
  • the signal receiver 3 includes a third optical filter 3-1, a second adjustable delay module 3-2, an electro-optic modulator 3-3, a third dispersion module 3-4, and a second photodetector 3- 5. Analog-to-digital conversion module 3-6, signal processing module 3-7.
  • the transceiver module includes a band selection switch 2-1, a first electrical amplifier array 2-2, a T/R component array 2-3, and an antenna array 2 4. Second electrical amplifier array 2-5.
  • the pulse signal outputted by the mode-locked laser 1-1 passes through the first dispersion module 1-2, and then splits into two parts by the first optical coupler 1-3, and a part enters the second optical coupler 1-4, and the other Part of entering the third light Filter 3-1.
  • the second optical coupler 1-4 divides the optical path into a first optical path and a second optical path, and the first optical path is a first optical filter 1-5, a second dispersion module 1-6 to the third
  • the optical coupler 1-9, the second optical path is a second optical filter 1-7, a first adjustable delay module 1-8, and a third optical coupler 1-9.
  • the third optical coupler 1-9 couples the signals of the first optical path and the second optical path together, and sequentially enters the optical amplifier 1-10 and the first photodetector 1-11.
  • the first photodetector 1-11 converts the optical signal into an electrical signal, and the electrical signal output by the first photodetector 1-11 is input to the transceiver module.
  • the band selection switch 2-1 will switch to the corresponding path, and the plurality of output ends of the band selection switch 2-1 are sequentially connected to the first electric amplifier array 2-2, T/R, respectively.
  • the component array 2-3 and the antenna array 2-4 form a plurality of vias.
  • the echo signals returned by the signal transmitted by the antenna array 2-4 through the measured object sequentially pass through the corresponding antenna array 2-4, the T/R component array 2-3, and the second electrical amplifier array 2-2 channel input.
  • the optical signal of the second output end of the first optical coupler 1-3 is input to the optical input of the electro-optic modulator 3-3 after sequentially passing through the third optical filter 3-1 and the second adjustable delay module 3-2. end.
  • the output signal of the electro-optic modulator 3-3 sequentially enters the signal processing module 3-7 through the third dispersion module 3-4, the second photodetector 4-5, and the analog-to-digital conversion module 3-6.
  • the generation of the wideband chirp signal is based on spectral filtering and the unbalanced dispersion ⁇ of the first optical path and the second optical path.
  • the center wavelength and the filtering bandwidth of the first tunable optical filter 1-5 and the second tunable optical filter 1-7 can be changed.
  • the transceiver module When signals of different bands are generated, the band selection switch is switched to the corresponding channel.
  • the transceiver module amplifies the signal generated by the signal transmitter and transmits it through the antenna, and receives and amplifies the echo signal.
  • Figure 3 shows the experimental results of the generated full-band covered UWB chirp signal, where (a) is the time domain waveform and (b) is the short time Fourier transform analysis.
  • the signal has a frequency range of approximately 5-60 GHz, a time width of ⁇ 23 ns, and a time bandwidth product of ⁇ 1265.
  • Figure 4 is the experimental results of the short-time Fourier transform analysis of the generated chirp signals of different bands, where (a) X-band (8-12 GHz), (b) Ku-band (12-18 GHz), (c) Ka band (26.5-40 GHz).
  • the signal generated by the signal transmitter verifies the capability of the full-band coverage or ultra-wideband radar system in either band.
  • FIG. 5 is a schematic diagram of single target detection and dual target detection using the X-band radar signal generated by the present invention as an example.
  • signal transmission and signal reception use two independent X-band horn antennas, and the two antennas are placed in parallel in the same direction, and the target to be detected is a metal plane perpendicular to the signal emission direction. If a transceiver antenna with T/R components is used, the effect is equivalent.
  • the echo signal of the transceiver module implements bandwidth compression and downconversion through a time stretch based receiving system.
  • the electrical signal is loaded onto the pre-dispersive optical pulse carrier by an electro-optic modulator to form a modulated optical signal corresponding to the electrical signal.
  • the filtering bandwidth of the third optical filter 3-4 needs to be larger than the filtering bandwidth of the first optical filter 1-5 and the second optical filter 1-7, and then the second adjustable delay module 3-2 is appropriately adjusted, so that The echoes of each target can be loaded onto the optical carrier.
  • An electrical signal that is stretched several times in time can be obtained through the second photodetector 3-5 through a third dispersion module 3-4 having a larger amount of dispersion.
  • FIG. 6 is a comparison of the time domain waveforms of the X-band chirp signals before and after the time stretching and the short-time Fourier transform analysis in single-target detection.
  • Fig. 6(a)(c) are the experimental results of the time domain waveform and the short-time Fourier transform analysis of the generated X-band signal, respectively, and
  • Fig. 6(b)(d) are the reflected X-band echo elapsed time, respectively.
  • the X-band signal is stretched in the time domain by about 5 times the original time, and the frequency and bandwidth of the signal are compressed by about 5 times.
  • the frequency and bandwidth of the compression after time stretching allows the feasibility of the pressure of the back-end signal quantization process to be attenuated.
  • FIG. 7 shows the test results for different target spacings in dual target detection.
  • Fig. 7(a) is a time domain waveform after a time stretch of ⁇ 6.3 cm
  • Fig. 7(b) is a time domain waveform after a time stretch of ⁇ 15.0 cm
  • Fig. 7(c) is When the distance is ⁇ 6.3cm, the positions of the two targets after the filtering process are matched, and Fig.
  • the X-band signal has undergone time stretching and frequency compression processing in the signal receiver, it still maintains the detection accuracy of the original UWB signal.

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Abstract

一种全波段覆盖的超宽带全光雷达系统，包括：信号发射机（1）、收发模块（2）、信号接收机（3）。该信号发射机（1）包括锁模激光器（1-1）、第一色散模块（1-2）、第一光耦合器（1-3）、第二光耦合器（1-4）、第一光滤波器（1-5）、第二色散模块（1-6）、第二光滤波器（1-7）、第一可调延时模块（1-8）、第三光耦合器（1-9）、光放大器（1-10）、第一光电探测器（1-11）；该收发模块（2）包括波段选择开关（2-1）、第一电放大器阵列（2-2）、T/R组件阵列（2-3）、天线阵列（2-4）、第二电放大器阵列（2-5）；信号接收机（3）包括第三光滤波器（3-1）、第二可调延时模块（3-2）、电光调制器（3-3）、第三色散模块（3-4）、第二光电探测器（3-5）、模拟-数字转换模块（3-6）、信号处理模块（3-7）。其具有宽带信号的中心频率、带宽和时间宽度的连续可调，相参高和测量精度高的特点。

Description

全波段覆盖的超宽带全光雷达系统 技术领域
本发明涉及微波光子学和雷达领域，具体是一种全波段覆盖的超宽带全光雷达系统。
背景技术
自20世纪80年代以来，随着光子学技术的发展，全光雷达的概念被提出并在国内外相关研究领域引起了广泛重视。由于光子学技术本身具有大带宽、低损耗、低抖动等优势，其在雷达系统中的应用可以突破传统的微波/毫米波雷达系统中存在的“电子瓶颈”的限制，为实现更高频率、更大带宽的宽带信号产生、接收和处理提供了新的技术途径。针对雷达系统对信号载频和捷变性的要求，意大利的P.Ghelfi等人基于光子学技术实现了全光相参雷达系统(参见P.Ghelfi,F.Laghezza,and F.Scotti,“A fully photonics-based coherent radar system,”Nature,vol.507,no.7492,pp.341-345,2014)。在该系统中，雷达信号的产生和接收基于同一台锁模激光器，从而保证了系统的高度相参，可有效抑制了相位噪声抖动，并提高了雷达的探测精度。在对40GHz工作频率的窄带雷达的演示验证中，该系统具有更高的量化保真度和测试精度。由于该系统的优异性能，P.Ghelfi等人的研究成果有望成为下一代雷达系统的设计准则(参见J.McKinney,“Technology:Photonics illuminates the future of radar,”Nature,2014,vol.507,no.7492,pp.310-312,Mar.2014)。
与其他无线电技术一样，雷达系统只能良好地工作在预先设计的波段上。多波段雷达可以同时或交叉选通地工作在不同波段，因此发现目标的概率比普通雷达高。多波段宽带雷达发射的信号包含许多频率分量，因此它能够突破窄频段吸波材料的吸波效应，有效提升雷达的反隐身探测能力。多波段雷达有利于抑制和回避敌方施放的干扰，对提高分辨率，降低多径损耗，增强自身的生存率都有积极作用。(参见束咸荣，何丙发.多频段雷达[C].信息产业部雷达专业情报网第十五届年会论文集.2003:26-32)。
在实际应用中，微波/毫米波雷达多采用以下信号形式：短脉冲信号、相位 编码信号及线性调频脉冲信号。在高精度测距中，短脉冲信号对脉冲的要求相当高，需要极窄的脉冲宽度，因此基于短脉冲信号的收发技术通常很难实现。相位编码信号按照一定的时间间隔在连续载波上加载相位信息来实现，其测试精度和旁瓣拟制比较高，但实现难度高且受多普勒效应的影响和本身动态范围的限制，不适用于大带宽系统。相比之下，线性调频脉冲信号在高精度的测距和雷达探测中应用广泛，调频带宽决定着测距精度，是微波/毫米波雷达系统的理想选择。
发明内容
本发明的目的在于克服上述现有技术的不足，提出一种全波段覆盖的超宽带全光雷达系统。采用同一台低抖动、宽光谱的锁模激光器分别产生和接收超宽带线性调频脉冲信号，确保收发系统的高相参和测量的高精度。信号发射机利用了锁模激光器的宽光谱和两臂上非平衡的色散啁啾，可实现超宽带信号的中心频率、带宽和时间宽度的连续可调，从而实现全波段覆盖或任一工作波段的超宽带雷达信号产生。信号接收机利用基于锁模激光器的时间拉伸技术压缩宽带信号的中心频率和带宽，大幅削弱后端模拟-数字转换和处理的压力，然而目标探测的距离分辨率仍然保持时间拉伸之前的精度。
为了实现上述目的，本发明的技术解决方案如下：
一种全波段覆盖的超宽带全光雷达系统，特电在于其构成包括信号发射机、收发模块和信号接收机；所述的信号发射机包括锁模激光器、第一色散模块、第一光耦合器、第二光耦合器、第一光滤波器、第二色散模块、第二光滤波器、第一可调延时模块、第三光耦合器、光放大器和第一光电探测器；所述的收发模块包括波段选择开关、第一电放大器阵列、T/R组件阵列、天线阵列、第二电放大器阵列；所述的信号接收机包括第三光滤波器、第二可调延时模块、电光调制器、第三色散模块、第二光电探测器、模拟-数字转换模块、信号处理模块，上述各部件的位置关系如下：
所述的锁模激光器输出端经第一色散模块接第一光耦合器的输入端，该第一光耦合器分为第一输出端和第二输出端：所述的第一光耦合器的第一输出端接第二光耦合器的输入端，所述的第二光耦合器将光路分为第一光路和第二光路，所述的第一光路依次是第一光滤波器、第二色散模块至第三光耦合器的输入端，所 述的第二光路依次是第二光滤波器、第一可调延时模块至第三光耦合器的输入端，所述的第三光耦合器将第一光路和第二光路的信号耦合到一起输出经光放大器进入第一光电探测器，该第一光电探测器将光信号转换为电信号输入到所述的收发模块的波段选择开关的输入端口，所述的波段选择开关具有2个以上输出端口，每个输出端口依次连接相应波段的第一电放大器阵列电放大器、T/R组件阵列的T/R组件和天线阵列的天线构成相应波段的通道，所述的天线阵列发射的电信号经代称目标返回的回波信号依次经过相应波段的天线阵列、T/R组件阵列、第二电放大器阵列的通道形成目标回波电信号，输入到所述的电光调制器(3－3)的射频输入端；
所述的第一光耦合器的第二输出端的光信号依次经过所述的第三光滤波器、第二可调延时模块输入到所述的电光调制器的光输入端形成光脉冲载波；
所述的电光调制器将所述的目标回波电信号加载到所述的的光脉冲载波上，形成与所述的目标回波电信号相对应的回波调制光信号，所述的电光调制器输出的回波调制光信号依次经过第三色散模块、第二光电探测器、模拟-数字转换模块进入所述的信号处理模块。
所述的锁模激光器是一台低抖动、宽谱的锁模激光器。
所述的第三光滤波器的滤波带宽大于第一光滤波器和第二光滤波器的滤波带宽。
在所述的信号发射机中，宽带线性调频信号的产生原理是基于光谱滤波及非平衡的色散啁啾(参见H.Zhang,W.Zou,and J.Chen,“Generation of widely tunable linearly-chirpedmicrowave waveform based on spectral filtering and unbalanced dispersion,”Optics Letters,vol.40,no.6,pp.1085-1088,2015)。通过调节第一可调光滤波器和第二可调光滤波器的中心波长和滤波带宽，以改变产生的宽带线性调频信号的中心频率和扫频带宽。
在所述的信号接收机中，收发模块输出的信号通过电光转换后，借鉴时间拉伸原理(参见Y.Han and B.Jalali,Photonic time-stretched analog-to-digital converter:Fundamental concepts and practical considerations,Journal of Lightwave Technology,vol.21,no.12,pp.3085-3103,2003)实现带宽压缩与下变频。雷达回波信号通过电光调制器加载到预先色散啁啾的光脉冲载波上，形成和雷达回波信号相对应的 调制光信号。第三光滤波器的滤波带宽需要大于第一光滤波器、第二光滤波器的滤波带宽，再适当调节第二可调延时模块，使得多个目标的回波都能加载到光载波上。通过一段有更大色散量的第三色散模块，经过第二光电探测器得到时间上被拉伸数倍的电信号。若第一色散模块和第三色散模块的色散系数分别为D1和D3，拉伸倍数M将由它们之比决定：
Figure PCTCN2015088463-appb-000001
待采样射频信号在时间上被拉伸，等效于频率域中被压缩，从而大幅削弱后端模拟-数字转换模块的带宽和采样率的压力。模拟-数字转换后的信号再通过数字信号处理提取出有用的目标信息，且目标探测的距离分辨率仍然保持时间拉伸之前的精度。
本发明具有以下优点：
1、本发明信号发射机和信号接收机基于相同的锁模激光器，可确保信号产生和处理过程的高度相参，从而大幅提高本发明的测量精度。
2、本发明通过调节第一光滤波器和第二光滤波器，可以产生全波段覆盖或任一波段的超宽带线性调频信号。
3、本发明的信号接收机利用了时间拉伸技术，将待采样信号在时间上拉伸、在频率域中压缩，从而大幅削弱后端模拟-数字转换模块的带宽和采样率的压力。
4、本发明的全波段覆盖或不同波段的雷达信号采用可切换的收发通道，实现了全波段覆盖的收发一体化。
5、本发明的目标探测分辨率由发射机产生的超宽带雷达信号带宽决定，与时间拉伸倍数无关。
附图说明
图1为本发明全波段覆盖的超宽带全光雷达系统的结构示意图。
图2为收发模块的结构示意图。
图3为产生的全波段覆盖的超宽带线性调频信号特征的测试结果。(a)时域波形，(b)短时傅里叶变换分析。
图4为产生的不同波段的线性调频信号的短时傅里叶变换分析的测试结果。(a)X波段，(b)Ku波段，(c)Ka波段。
图5为使用所产生的X波段信号作为示例，进行的单目标探测和双目标探测的实验示意图。(a)单目标，(b)双目标。
图6为单目标探测中，时间拉伸前后X波段线性调频信号的时域波形及其短时傅里叶变换分析的测试结果。(a)拉伸前时域波形，(b)拉伸后时域波形，(c)拉伸前短时傅里叶变换分析，(d)拉伸后短时傅里叶变换分析。
图7为双目标探测中，不同目标间距时的测试结果。(a)当距离为～6.3cm，时间拉伸后的时域波形，(b)当距离为～15.0cm，时间拉伸后的时域波形，(c)当距离为～6.3cm，匹配滤波处理后两个目标的位置，(d)当距离为～15.0cm，匹配滤波处理后两个目标的位置。
具体实施方式
下面结合附图给出本发明的一个具体实施例。本实施例以本发明的技术方案为前提进行实施，给出了详细的实施方式和过程，但本发明的保护范围不应限于下述的实施例。
图1为本发明全波段覆盖的超宽带全光雷达系统的结构示意图，如图所示，一种全波段覆盖的超宽带全光雷达系统包括信号发射机1、收发模块2和信号接收机3。所述的信号发射机1包括锁模激光器1-1、第一色散模块1-2、第一光耦合器1-3、第二光耦合器1-4、第一光滤波器1-5、第二色散模块1-6、第二光滤波器1-7、第一可调延时模块1-8、第三光耦合器1-9、光放大器1-10、第一光电探测器1-11；
所述的信号接收机3包括第三光滤波器3-1、第二可调延时模块3-2、电光调制器3-3、第三色散模块3-4、第二光电探测器3-5、模拟-数字转换模块3-6、信号处理模块3-7。
图2为所述的收发模块2的结构示意图，如图所示，收发模块包括波段选择开关2-1、第一电放大器阵列2-2、T/R组件阵列2-3、天线阵列2-4、第二电放大器阵列2-5。
上述元部件的连接关系如下：
所述的锁模激光器1-1输出的脉冲信号先经过第一色散模块1-2，再由第一光耦合器1-3分为两部分，一部分进入第二光耦合器1-4，另一部分进入第三光 滤波器3-1。第二光耦合器1-4将光路分为第一光路和第二光路，所述的第一光路依次是第一光滤波器1-5、第二色散模块1-6至所述的第三光耦合器1-9，所述的第二光路依次是第二光滤波器1-7、第一可调延时模块1-8至所述的第三光耦合器1-9。该第三光耦合器1-9将第一光路和第二光路的信号耦合到一起，依次进入光放大器1-10、第一光电探测器1-11。所述的第一光电探测器1-11将光信号转换为电信号，第一光电探测器1-11输出的电信号输入到收发模块。根据信号的波段，所述的波段选择开关2-1将切换到对应的通路，所述的波段选择开关2-1的多个输出端分别依次连接第一电放大器阵列2-2、T/R组件阵列2-3、天线阵列2-4形成多个通路。经所述的天线阵列2-4发射的信号经被测物体返回的回波信号依次经过相应的天线阵列2-4、T/R组件阵列2-3和第二电放大器阵列2-2通道输入所述的电光调制器3-3的射频输入端。第一光耦合器1-3的第二输出端的光信号在依次经过第三光滤波器3-1、第二可调延时模块3-2后，输入到电光调制器3-3的光输入端。所述的电光调制器3-3的输出信号依次经过第三色散模块3-4、第二光电探测器4-5、模拟-数字转换模块3-6进入所述的信号处理模块3-7。
本发明的工作原理如下：
在图1的信号发射机中，宽带线性调频信号的产生是基于光谱滤波及第一光路、第二光路上非平衡的色散啁啾。通过调节第一可调光滤波器1-5和第二可调光滤波器1-7的中心波长和滤波带宽，可以改变产生的宽带线性调频信号的中心频率和扫频带宽。
图2为收发模块的结构示意图。当产生不同波段的信号时，波段选择开关切换到对应通道。收发模块将信号发射机产生的信号经过放大后通过天线发射出去，并接收、放大回波信号。
图3为产生的全波段覆盖的超宽带线性调频信号的实验结果，其中，(a)为时域波形、(b)为短时傅里叶变换分析。信号的频率范围约为5-60GHz，时间宽度为～23ns，时间带宽积达到～1265。
图4为产生的不同波段的线性调频信号的短时傅里叶变换分析的实验结果，其中，(a)X波段(8-12GHz)，(b)Ku波段(12-18GHz)，(c)Ka波段(26.5-40GHz)。信号发射机产生的信号验证了全波段覆盖或任一波段的超宽带雷达系统能力。
为了验证本发明的可行性，信号发射机产生X波段雷达信号对目标进行探测，信号接收机接收回波信号进行初步实验验证。图5为使用本发明所产生的X波段雷达信号为例，进行单目标探测和双目标探测的示意图。在图5(a)(b)中，信号发射和信号接收使用两个独立的X波段喇叭天线，两天线同方向平行地放置，待探测的目标是垂直于信号发射方向的金属平面。若采用含T/R组件的收发一体天线，效果等同。
在所述的信号接收机中，收发模块的回波信号通过基于时间拉伸的接收系统实现带宽压缩与下变频。利用时间拉伸原理，电信号通过电光调制器加载到预先色散啁啾的光脉冲载波上，形成和电信号相对应的调制光信号。第三光滤波器3-4的滤波带宽需要大于第一光滤波器1-5、第二光滤波器1-7的滤波带宽，再适当调节第二可调延时模块3-2，使得多个目标的回波都能加载到光载波上。通过一段有更大色散量的第三色散模块3-4，经过第二光电探测器3-5可以得到时间上被拉伸数倍的电信号。待采样射频信号在时间上被拉伸，等效于频率域中被压缩，从而大幅削弱后端模拟-数字转换模块3-6的带宽和采样率的压力。图6为单目标探测中，时间拉伸前后X波段线性调频信号的时域波形及其短时傅里叶变换分析对比图。图6(a)(c)分别为所产生的X波段信号的时域波形和短时傅里叶变换分析的实验结果，图6(b)(d)分别为反射的X波段回波经过时间拉伸后的时域波形和短时傅里叶变换分析的实验结果。经过时间拉伸，X波段信号在时域上拉伸约为原来时间的5倍，信号的频率和带宽均被压缩了约5倍。时间拉伸后被压缩的频率和带宽使后端信号量化处理的压力被削弱的可行性得以验证。
利用宽带线性调频信号进行目标探测可获得较好的目标特性，距离分辨率由发射信号的带宽决定。模拟-数字转换后的信号再通过数字信号处理提取出有用的目标信息。目标探测的距离分辨率仍然保持时间拉伸之前的精度。图7为双目标探测中不同目标间距时的测试结果。图7(a)是当距离为～6.3cm，时间拉伸后的时域波形，图7(b)是当距离为～15.0cm，时间拉伸后的时域波形，图7(c)是当距离为～6.3cm，匹配滤波处理后两个目标的位置，图7(d)是当距离为～15.0cm，匹配滤波处理后两个目标的位置。X波段信号虽然在信号接收机中经过了时间拉伸及频率压缩处理，但是仍然保持原有超宽带信号的探测精度。

Claims (3)

  1. 一种全波段覆盖的超宽带全光雷达系统，特征在于其构成包括信号发射机(1)、收发模块(2)和信号接收机(3)；
    所述的信号发射机(1)包括锁模激光器(1-1)、第一色散模块(1-2)、第一光耦合器(1-3)、第二光耦合器(1-4)、第一光滤波器(1-5)、第二色散模块(1-6)、第二光滤波器(1-7)、第一可调延时模块(1-8)、第三光耦合器(1-9)、光放大器(1-10)和第一光电探测器(1-11)；
    所述的收发模块(2)包括波段选择开关(2-1)、第一电放大器阵列(2-2)、T/R组件阵列(2-3)、天线阵列(2-4)、第二电放大器阵列(2-5)；
    所述的信号接收机(3)包括第三光滤波器(3-1)、第二可调延时模块(3-2)、电光调制器(3-3)、第三色散模块(3-4)、第二光电探测器(3-5)、模拟-数字转换模块(3-6)和信号处理模块(3-7)；
    上述各部件的位置关系如下：
    所述的锁模激光器(1-1)输出端经第一色散模块(1-2)接第一光耦合器(1-3)的输入端，该第一光耦合器(1-3)分为第一输出端和第二输出端：所述的第一光耦合器(1-3)的第一输出端接第二光耦合器(1-4)的输入端，所述的第二光耦合器(1-4)将光路分为第一光路和第二光路，所述的第一光路依次是第一光滤波器(1-5)、第二色散模块(1-6)至第三光耦合器(1-9)的输入端，所述的第二光路依次是第二光滤波器(1-7)、第一可调延时模块(1-8)至第三光耦合器(1-9)的输入端，所述的第三光耦合器(1-9)将第一光路和第二光路的信号耦合到一起输出经光放大器(1-10)进入第一光电探测器(1-11)，该第一光电探测器(1-11)将光信号转换为电信号输入到所述的收发模块(2)的波段选择开关(2-1)的输入端口，所述的波段选择开关(2-1)具有2个以上输出端口，每个输出端口依次连接相应波段的第一电放大器阵列(2-2)的电放大器、T/R组件阵列(2-3)的T/R组件和天线阵列(2-4)的天线构成相应波段的通道，所述的天线阵列(2-4)发射的电信号经待测目标返回的回波信号依次经过相应波段的天线阵列(2-4)、T/R组件阵列(2-3)、第二电放大器阵列(2-5)的通道形成目标回波电信号，输入到所述的电光调制器(3-3)的射频输入端；
    所述的第一光耦合器(1-3)的第二输出端的光信号依次经过所述的第三光滤波器(3-1)、第二可调延时模块(3-2)输入到所述的电光调制器(3-3)的光输入端形成光脉冲载波；
    在所述的电光调制器(3-3)中所述的目标回波电信号加载到所述的光脉冲载波上，形成与所述的目标回波电信号相对应的回波调制光信号，所述的电光调制器(3-3)输出的该回波调制光信号依次经过第三色散模块(3-4)、第二光电探测器(4-5)、模拟-数字转换模块(3-6)进入所述的信号处理模块(3-7)。
  2. 根据权利要求1所述的全波段覆盖的超宽带全光雷达系统，其特征在于所述的锁模激光器是一台低抖动、宽谱的锁模激光器。
  3. 根据权利要求1或2所述的全波段覆盖的超宽带全光雷达系统，其特征在于所述的第三光滤波器的滤波带宽大于第一光滤波器和第二光滤波器的滤波带宽。
PCT/CN2015/088463 2015-08-17 2015-08-29 全波段覆盖的超宽带全光雷达系统 WO2017028335A1 (zh)

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