Controlled agile laser chaotic signal generator and polymorphic chaotic agile laser radar

Abstract

The invention proposes a controlled agile laser chaotic signal generator and a multi-state chaotic agile laser radar, belonging to the field of remote sensing ranging signals; the controlled agile laser chaotic signal generator comprises a first semiconductor laser, a second semiconductor laser, a first optical isolator, a second optical isolator, a first optical coupler, a first photodetector, an electrically controlled polarization regulator, a second optical coupler, a third optical coupler, a second photodetector, a first output port, a second output port, an input port, and an FPGA controller; the controlled agile laser chaotic signal generator of the invention adopts a method of optically injecting semiconductor lasers to obtain a high-bandwidth laser chaotic signal at the GHz level, which has outstanding ultra-wideband properties and excellent anti-interference performance; the invention can be expanded into a method of optical injection of multiple lasers to generate chaotic signals with higher bandwidth; the invention realizes rapid switching between chaotic states, so that the chaotic signal has agile properties and enhances the anti-interference ability.

Description

Technical Field

[0001] The invention belongs to the field of radar signals, and in particular relates to a controlled agile laser chaos signal generator and a polymorphic chaotic agile laser radar. Technical Background

[0002] In today's optoelectronic attack and defense confrontation, optoelectronic anti-interference technology has become an essential means of attack or defense. In recent years, with the development of microelectronics integration technology, it has been technically possible to achieve high-speed sampling, signal replication, frequency analysis, data storage and other functions of radar signals. This has led to the fact that radar signals with fixed parameters in modern warfare are often easily intercepted by enemy jammers. These jammers can quickly analyze and quickly generate jamming signals, posing a serious interference threat to conventional radars. In addition, laser ranging is widely used in military, national defense and industrial production as a precise ranging method, but ordinary laser ranging cannot avoid the interference problem of the same system. In the field of modern unmanned vehicle driving technology, the complex real traffic environment also leads to a large amount of strong interference in the real working scene of laser chaos radar. Therefore, how to significantly improve the anti-interference performance of laser radar has become a hot issue of concern to researchers.

[0003] Chaotic radar uses deterministic non-periodic signals, which have stronger electronic anti-interference capabilities than other radar solutions. Laser chaotic signals have noise-like characteristics, non-periodic, delta-function-like autocorrelation properties, and therefore naturally have good anti-interference performance. The bandwidth of chaotic signals generated by traditional microwave circuits is less than 1 GHZ. In order to improve radar resolution, the laser chaotic signals generated by optical injection have significant ultra-wideband characteristics, and their bandwidth can reach the GHz spectrum range, meeting the needs of high-resolution radar imaging and target recognition.

[0004] Agile frequency radar is another direction of radar anti-interference research. It has attracted extensive attention from researchers due to its excellent anti-interference performance. Agile frequency radar generally sets multiple frequency hopping points within the bandwidth range. The adjacent pulse signals transmitted randomly jump within the frequency point, and the single frequency point stays for a very short time. Compared with radars with fixed parameters, frequency agile radars make it difficult for jammers such as superheterodyne receivers to quickly intercept information. It has the advantages of strong anti-interference ability and low interception rate. In addition, as the radar gets closer and closer to the target, the random changes in the scattering intensity and relative phase of different parts of the complex target cause the echo to tilt and randomly swing on the aperture plane of the receiving antenna, resulting in measurement errors, which are called angular glints. The random jumping of adjacent pulses of the agile frequency radar can effectively eliminate the correlation between adjacent pulses and suppress the angular glint effect. Summary of the invention

[0005] The present invention combines ultra-wideband laser chaos with the modal agility method, and proposes an ultra-wideband multi-state chaotic agile laser radar scheme, which has a dual anti-interference mechanism of ultra-wideband laser chaos signal and agile frequency radar. This scheme can quickly switch modal characteristics within an ultra-wide frequency spectrum, has strong anti-interference performance, and is suitable for intense optoelectronic confrontation scenarios and complex unmanned driving scenarios.

[0006] The present invention proposes a GHz ultra-wideband polymorphic chaotic agile laser radar system design. The advantages of ultra-wideband chaotic laser radar and agile radar are taken into account in the design, and the agile characteristics are introduced into the laser chaotic radar, so that the scheme has very excellent anti-interference performance. After testing, the system can work in a strong interference environment. When the interference signal strength of the environment is 5 times the echo signal strength, the peak of the cross-correlation curve calculated by the signal processing module is clearly visible. When the interference signal strength is 50 times the echo signal strength, the peak value of the cross-correlation curve is small, but it can still be clearly observed, indicating that the system design has good performance in a strong interference environment.

[0007] The technical solution adopted by the present invention is: a controlled agile laser chaotic signal generator, including a first semiconductor laser, a second semiconductor laser, a first optical isolator, a second optical isolator, a first optical coupler, a first photodetector, an electrically controlled polarization regulator, a second optical coupler, a third optical coupler, a second photodetector, a first output port, a second output port, an input port, and an FPGA controller; wherein the first semiconductor laser is used to generate continuous laser output to the first optical isolator; the first optical isolator is used to isolate unnecessary reflected light, improve the light wave transmission efficiency, and input it into the first optical coupler; the first optical coupler is 90 :10 optical coupler, used to divide the light generated by the first semiconductor laser into two paths: the light intensity of the first path is 10% of the input light intensity, which is input into the first photodetector, and the light intensity of the second path is 90% of the input light intensity, which is input into the electrically controlled polarization regulator; the first photodetector is used to convert the received optical signal into an electrical signal with high fidelity, and input it into the FPGA controller through the first output port; the electrically controlled polarization regulator is controlled by the FPGA controller through the input port, and is used to quickly convert the polarization state of the input laser into any polarization state. The selection of the polarization state is controlled by the FPGA controller, and the laser with any polarization state is obtained. The light is injected into the second optical coupler; the second semiconductor laser is also used to generate continuous laser light and is input into the second optical isolator. The second optical isolator is used to isolate unnecessary reflected light, improve the light wave transmission efficiency, and is input into the second optical coupler; the second optical coupler is a 50:50 optical coupler, which is used to couple the laser light of any polarization state output by the electrically controlled polarization regulator into the continuous laser light generated by the second semiconductor laser to generate an ultra-wideband chaotic laser signal, the ultra-wideband chaotic laser signal can reach GHz, and the generated ultra-wideband chaotic laser signal is input into the third optical coupler; the third optical coupler is a 90:10 optical coupler The device is used to divide the ultra-wideband chaotic laser signal into two paths, the intensity of the first path of chaotic laser is 10% of the intensity of the input ultra-wideband chaotic laser signal, and is input into the second photodetector as detection light, and the intensity of the second path of chaotic laser is 90% of the intensity of the input ultra-wideband chaotic laser signal, and is used as the final output chaotic signal; the second photodetector is used to convert the first path of ultra-wideband chaotic laser signal into an electrical signal with high fidelity, and output it to the FPGA controller through the second output port, and the FPGA controller is used to receive the signals input from the first output port and the second output port, and is connected to the electrically controlled polarization regulator through the output port to control the switching of the chaotic state.

[0008] Furthermore, by expanding the method into multi-laser optical injection, laser chaotic signals with higher bandwidth can be generated.

[0009] Furthermore, the electrically controlled polarization regulator is a FT-OM-PC-M4 electrically controlled polarization regulator.

[0010] Furthermore, the ultra-wideband chaotic laser signal can be expanded into more modes, for example, it can be set to 16, 32, or 64 different chaotic states, which is suitable for a variety of ultra-wideband solutions.

[0011] The present invention also provides a polymorphic chaotic agile laser radar, comprising a signal generating module, a signal transmitting and receiving module and a signal processing module.

[0012] The signal generating module is a controlled agile laser chaotic signal generator, which is used to generate an ultra-wideband chaotic laser signal.

[0013] The signal transmitting and receiving module is used to transmit the ultra-wideband chaotic laser signal generated by the controlled agile laser chaotic signal generator and receive the echo signal, including an isolator, a first optical amplifier, a beam splitter, a collimator, a beam expander, a third photodetector, a fourth photodetector, a second optical amplifier, and a telescope collecting device; the ultra-wideband chaotic laser signal generated by the controlled agile laser chaotic signal generator is connected to the isolator through a 62.5um multimode optical fiber, and the isolator is used to isolate the reflected light in the ultra-wideband chaotic laser signal to reduce unnecessary interference, and input the ultra-wideband chaotic laser signal into the first optical amplifier; the first optical amplifier is used to amplify the ultra-wideband chaotic laser signal, and the amplified ultra-wideband chaotic laser signal is output to the beam splitter; the beam splitter is used to split the light into two Path: The first path of light is input into the collimator, and the second path of light is input into the third photodetector; the collimator is used to convert the first path of light into a parallel collimated light column and output it to the beam expander; the beam expander is used to expand the diameter of the input parallel collimated light column and transmit it to the target; the third photodetector is used to convert the second path of light into an electrical signal with high fidelity, which is input into the signal processing module as a reference signal of the transmission signal; the telescope collecting device is used to efficiently collect the echo signal returned from the target and output it to the second optical amplifier; the second optical amplifier is used to amplify the echo signal, enhance the intensity of the echo signal, and output it to the fourth photodetector; the fourth photodetector is used to convert the amplified echo signal into an electrical signal and input it into the signal processing module.

[0014] The signal processing module uses the excellent autocorrelation characteristics of chaotic signals and obtains high-resolution target distance information through cross-correlation calculation and processing. The calculation and processing methods can be found in the literature (Chaotic lidar, IEEE, Lin FY and Liu JM, SEP-OCT 2004).

[0015] The present invention has the following technical effects:

[0016] 1. The controlled agile laser chaotic signal generator uses the method of optically injected semiconductor lasers to obtain GHz-level high-bandwidth laser chaotic signals with outstanding ultra-wideband properties and excellent anti-interference performance;

[0017] 2. This scheme uses the method of injecting the light generated by a semiconductor laser into another laser to generate a chaotic signal, which can be expanded into a multi-laser optical injection method to generate a chaotic signal with a higher bandwidth;

[0018] 3. This scheme uses a high-performance electrically controlled polarization regulator to achieve fast switching between chaotic states, making the chaotic signal agile and further enhancing the anti-interference ability;

[0019] 4. The controlled agile laser chaotic signal generator generates polymorphic broadband optical chaos. This scheme sets up 16 chaotic signals of different modes, which can be expanded into more modal spaces in theory. The number of chaotic states can be set to 32, 64, etc. according to needs without making too many changes to the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a specific implementation method of a controlled agile laser chaotic signal generator;

[0021] Figure 2 It is a schematic diagram of the structure of a polymorphic chaotic agile laser radar, which includes three modules: a signal generation module, a signal transmission and reception module, and a signal processing module;

[0022] Figure 3 It is the waveform diagram, spectrum diagram and cross-correlation curve diagram of chaotic state 1;

[0023] Figure 4 It is the waveform diagram, spectrum diagram and cross-correlation curve diagram of chaotic state 3;

[0024] Figure 5 It is the waveform diagram, spectrum diagram and cross-correlation curve diagram of chaotic state 13;

[0025] Figure 6 It is the waveform diagram, spectrum diagram and cross-correlation curve diagram of chaotic state 15;

[0026] Figure 7 It is the cross-correlation curve of the anti-interference test of the polymorphic chaotic agile laser radar;

[0027] Figure 8 It is a transmission signal waveform diagram, echo signal waveform diagram and cross-correlation curve diagram containing 16 chaotic state sequences; Specific implementation plan

[0028] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0029] Attached Figure 1 It is a structural schematic diagram of a specific implementation of a controlled agile laser chaotic signal generator, which is responsible for generating a polymorphic chaotic signal. The specific steps and principles are as follows: The device comprises two laser generators: a first semiconductor laser and a second semiconductor laser. The threshold current of the first semiconductor laser is 18mA, and the bias current is fixed at 38mA. The threshold current of the second semiconductor laser is 17mA, and the bias current is fixed at 105mA. The ambient temperature is 25°C. An ultra-wideband chaotic signal is generated by injecting the laser of the first semiconductor laser into the second semiconductor laser. In the experiment, the input currents of the two semiconductor lasers are controlled to remain unchanged. When the polarization states of the lasers injected into the second semiconductor laser are the same, although the generated chaotic signals are different, the generated chaotic signals have very similar frequency distributions. This chaotic signal with similar frequency distribution is set to a chaotic state. In this device, 16 different chaotic states are set. The switching of different chaotic states can be achieved by controlling a high-performance electrically controlled polarization regulator (model FT-OM-PC-M4, working wavelength 1260nm-1650nm, inherent insertion loss (0.4dB)) through an FPGA controller. The response speed of the polarization controller reaches 30μs, which can meet the requirements of fast switching of chaotic states. In order to facilitate the FPGA controller to switch between different chaotic states, in the control program, these pre-set chaotic states are respectively corresponded to a frequency hopping code (represented by numbers 1-16). Each group of chaotic signals transmitted contains 16 chaotic states, and the duration of each chaotic state is 1ms. The transmission order of these 16 chaotic states depends on the arrangement order of the frequency hopping codes. These frequency hopping codes are combined and mapped through an algorithm to generate a combination mapping code containing 16 frequency hopping codes. The FPGA controller controls the electrically controlled polarization regulator to generate an ultra-wideband agile chaotic state sequence in the order of the combination mapping code based on the generated combination mapping code.

[0030] Attached Figure 2 The system diagram of the present invention includes three modules: signal generation module, signal transmission and reception module and signal processing module:

[0031] Module 1 is a signal generation module, which is a controlled agile laser chaotic signal generator responsible for generating multi-state agile chaotic laser signals. The photodetector used is a high-speed, low-noise InGaAs photodetector that can detect chaotic light with a bandwidth of 12.5 GHz, which can meet the needs of the system.

[0032] Module 2 is the signal transmitting and receiving module, which is responsible for transmitting the multi-state agile chaotic laser signal generated by the signal generation module and processing the received echo signal. The isolator uses MCHI-1550, which can withstand a power of 20w and an operating wavelength of 1550nm; the first optical amplifier uses a semiconductor optical amplifier, the specific model is AA3F215CA, which can obtain a gain greater than 15dB and can meet the system amplification requirements; the beam expander uses HBE-1064-2X, ​​which can expand the light beam to twice its original size.

[0033] Module three is the signal processing module, which uses the excellent autocorrelation characteristics of chaotic signals to obtain high-resolution target distance information through cross-correlation calculation.

[0034] Attached Figure 3 To the attached Figure 6 The following are the relevant waveforms, spectra and cross-correlation curves of four chaotic states (chaotic states 1, 3, 13 and 15) selected from the 16 chaotic states. The experimental chaotic waveforms were collected using a high-speed digital storage oscilloscope (DSO9404A, bandwidth 4GHz, sampling rate 20GS / s), and the spectrum signals were collected using a spectrum analyzer (RSA507A, frequency range 9kHz-7.5GHz). (a) and (b) are the waveforms of the transmitted signal and the echo signal within 1μs, respectively. (d) and (e) are the chaos curves of the first 1000 points of (a) and (b), respectively. It can be seen that the chaotic signal is a noise-like signal. (c) is the spectrum distribution of the four chaotic states. The spectrum shows that the frequency distribution of the four chaotic states is quite different. (f) is the cross-correlation curve between the transmitted signal and the echo signal. The peak values ​​of the cross-correlation curves of the four chaotic states all exceed 0.6, indicating that there is a strong cross-correlation between the transmitted signal and the echo signal. The full width at half maximum (FWHM) of chaotic state 3 is 0.60 ns, indicating that the system has a high resolution of 9 cm.

[0035] Attached Figure 7This is the cross-correlation curve of the anti-interference test of the polymorphic chaotic agile laser radar. The test uses chaotic state 15, the transmission signal strength is -20dB, the ambient temperature is 25℃, and the interference signal strength is set to -23dB. (a) is the anti-interference test 1, its echo signal strength is -23dB, which is consistent with the interference signal strength. The transmission signal and the echo signal are cross-correlated. The peak value of the cross-correlation obtained from the curve is 0.48, and the peak half-width is 0.88ns, indicating that when the interference signal strength and the echo signal strength are the same, the system shows good anti-interference ability and high resolution; (b) is the anti-interference test 2, other conditions remain unchanged, only the echo signal strength is reduced, and its strength is set to -30dB, and then the transmission signal and the echo signal are cross-correlated. The test results show that the curve is cross-correlated. The peak value is 0.10, and the peak half width is 0.92ns. The peak value of the cross-correlation can still be clearly observed, indicating that when the interference signal is 5 times stronger than the signal strength at the receiving end, the system can still work normally; (c) is the anti-interference test 3. Other conditions remain unchanged, and the echo signal strength continues to be reduced to -40dB. At this time, the interference signal strength is about 50 times the echo signal strength. The transmission signal and the echo signal are also cross-correlated. This time, the cross-correlation peak value is 0.02. The cross-correlation peak value is significantly smaller than before, but it can still be observed. The system is still robust under strong interference. The above anti-interference test shows that the polymorphic chaotic agile signal generated by the system has strong anti-interference and high-resolution distance. When the interference signal strength is several times or even dozens of times stronger than the echo signal, the entire system can still work.

[0036] Attached Figure 8 It is a transmission signal waveform diagram, echo signal waveform diagram and cross-correlation curve diagram containing 16 chaotic state sequences. The transmission signal is a chaotic sequence, which is mapped by the combination of 16 chaotic states. (a) is a multi-state chaotic sequence. The frequency hopping code is a combination of numbers 1-16, which is a combination of a string of 16 numbers randomly generated by the FPGA program. Each number corresponds to a chaotic state. The FPGA program controls the electric polarization controller according to the generated frequency hopping code to generate the corresponding chaotic state. The switching interval of the electric polarization controller is t=1ms. The set chaotic state is transmitted according to the frequency hopping code sequence. The transmission signal obtained is a multi-state chaotic state. Chaotic sequence, for example, the frequency hopping code of (a) is {5, 8, 15, 2, 6, 14, 1, 16, 4, 3, 11, 9, 13, 7, 10, 12}, and its combined chaotic waveform is obtained; (b) is the chaotic waveform of the echo signal corresponding to (a). For the combined chaotic sequence, it still has a strong autocorrelation characteristic. The cross-correlation calculation of the transmitted chaotic sequence signal and the echo signal is performed to obtain the cross-correlation curve (c), whose peak value is about 0.70, indicating that this chaotic sequence has good cross-correlation and can realize the target positioning and ranging functions.

Claims

1. A controlled agile laser chaotic signal generator, characterized in that: The invention comprises a first semiconductor laser, a second semiconductor laser, a first optical isolator, a second optical isolator, a first optical coupler, a first photodetector, an electrically controlled polarization regulator, a second optical coupler, a third optical coupler, a second photodetector, a first output port, a second output port, an input port, and an FPGA controller; wherein the first semiconductor laser is used to generate continuous laser light and output it to the first optical isolator; the first optical isolator is used to isolate unnecessary reflected light, improve the light wave transmission efficiency, and input it into the first optical coupler; the first optical coupler is a 90:10 optical coupler, which is used to generate the first semiconductor laser. The light is divided into two paths: the first path has a light intensity of 10% of the input light intensity and is input into the first photodetector, and the second path has a light intensity of 90% of the input light intensity and is input into the electrically controlled polarization regulator; the first photodetector is used to convert the received optical signal into an electrical signal with high fidelity and input it into the FPGA controller through the first output port; the electrically controlled polarization regulator is controlled by the FPGA controller through the input port and is used to quickly convert the polarization state of the input laser into any polarization state. The selection of the polarization state is controlled by the FPGA controller, and the laser with any polarization state is injected into the second optical coupler; the second The semiconductor laser is also used to generate continuous laser light and input it into the second optical isolator. The second optical isolator is used to isolate unnecessary reflected light, improve the light wave transmission efficiency, and input it into the second optical coupler. The second optical coupler is a 50:50 optical coupler, which is used to couple the laser light of any polarization state output by the electrically controlled polarization regulator into the continuous laser light generated by the second semiconductor laser to generate an ultra-wideband chaotic laser signal. The ultra-wideband chaotic laser signal can reach GHz. The generated ultra-wideband chaotic laser signal is input into the third optical coupler. The third optical coupler is a 90:10 optical coupler, which is used to couple the ultra-wideband chaotic laser signal to the continuous laser light generated by the second semiconductor laser. The chaotic laser signal is divided into two paths. The intensity of the first chaotic laser is 10% of the intensity of the input ultra-wideband chaotic laser signal, which is input into the second photodetector as detection light. The intensity of the second chaotic laser is 90% of the intensity of the input ultra-wideband chaotic laser signal, which is used as the final output chaotic signal. The second photodetector is used to convert the first ultra-wideband chaotic laser signal into an electrical signal with high fidelity, and output it to the FPGA controller through the second output port. The FPGA controller is used to receive the signals input from the first output port and the second output port, and is connected to the electrically controlled polarization regulator through the output port to control the switching of the chaotic state.

2. A controlled agile laser chaotic signal generator according to claim 1, characterized in that: The electrically controlled polarization regulator is a FT-OM-PC-M4 type electrically controlled polarization regulator.

3. A polymorphic chaotic agile laser radar using the controlled agile laser chaotic signal generator according to claim 1, characterized in that: The invention comprises a signal generating module, a signal transmitting and receiving module and a signal processing module; the signal generating module is a controlled agile laser chaotic signal generator, which is used to generate an ultra-wideband chaotic laser signal; the signal transmitting and receiving module is used to transmit the ultra-wideband chaotic laser signal generated by the controlled agile laser chaotic signal generator and receive the echo signal, and comprises an isolator, a first optical amplifier, a beam splitter, a collimator, a beam expander, a third photoelectric detector, a fourth photoelectric detector, a second optical amplifier and a telescope collecting device; the ultra-wideband chaotic laser signal generated by the controlled agile laser chaotic signal generator is transmitted through a 62 A .5um multimode optical fiber is connected to an isolator, the isolator is used to isolate the reflected light in the ultra-wideband chaotic laser signal, reduce unnecessary interference, and input the ultra-wideband chaotic laser signal into the first optical amplifier; the first optical amplifier is used to amplify the ultra-wideband chaotic laser signal, and the amplified ultra-wideband chaotic laser signal is output to the beam splitter; the beam splitter is used to split the light into two paths: the first path of light is input into the collimator, and the second path of light is input into the third photodetector; the collimator is used to convert the first path of light into a beam of parallel collimated light beams, and output it to the beam expander; the beam expander is used to expand the diameter of the input parallel collimated light beams and emit them to the target; A third photoelectric detector is used to convert the second light into an electrical signal with high fidelity, which is input into the signal processing module as a reference signal of the transmission signal; A telescope collecting device, used to efficiently collect the echo signal returned from the target and output it to the second optical amplifier; The second optical amplifier is used to amplify the echo signal, enhance the intensity of the echo signal, and output it to the fourth photodetector; the fourth photodetector is used to convert the amplified echo signal into an electrical signal and input it into the signal processing module; the signal processing module utilizes the excellent autocorrelation characteristics of the chaotic signal and obtains high-resolution target distance information through cross-correlation calculation processing.

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