A terahertz radar system based on chaotic signals

Abstract

The present invention discloses a terahertz radar system based on chaotic signals, comprising: a signal transmission link and a signal receiving link, wherein the signal transmission link is used to generate and transmit a terahertz chaotic signal to a target object, and the signal receiving link is used to process and obtain perception information based on the reflected signal of the terahertz chaotic signal acting on the target object. The radar system provided by the present invention uses a flexible optical architecture to generate a terahertz chaotic signal as a radar detection signal, which can improve the radar detection accuracy and clarity, and at the same time improve the safety and anti-interference of the radar system.

Description

Technical Field

[0001] The invention belongs to the technical field of radars, and in particular relates to a terahertz radar system based on chaotic signals. Background Art

[0002] Terahertz (THz) waves, with frequencies between 0.1 THz and 10 THz, have attracted widespread attention due to their rich bandwidth resources, low energy, and high environmental robustness. In particular, THz radar systems have good anti-interference capabilities against smoke or haze, and have rich spectrum resources to provide high resolution, so they have been widely studied. For classical radar signals in modern THz radar systems, such as those based on periodic signals (such as frequency modulated continuous wave (FMCW) or frequency modulated pulse wave (FMPW)), they have been widely adopted and have made significant progress in ranging resolution. However, the limited bandwidth of traditional signal sources restricts the ability to carry a large amount of precise target information. The inherent ranging ambiguity of periodic radar signals also limits the practical application of THz radar systems. In addition, considering the open nature of THz sensing links, THz radar systems face the challenges of interference and attacks, which not only threaten the security of the system but also affect the sensing performance. In this context, chaos theory shows the potential to solve the above problems, enabling unambiguous ranging and enhancing the security and anti-interference of THz radar systems. The bandwidth of chaotic radar signals generated by traditional nonlinear dynamic circuits is limited by the bandwidth of electronic components, which affects the perception performance of THz radar. In contrast, chaotic radar technology based on photonics is expected to achieve better detection performance.

[0003] Ziwei Xu et al. published an article titled "High-resolution radar ranging based on the ultra-wideband chaotic optoelectronic oscillator" in the journal Optics Express in 2023. The article uses an intensity modulator to construct an optoelectronic oscillator loop to realize chaotic radar. The radar system generates a broadband chaotic signal of 2GHz to 16GHz and radiates it into free space to achieve target detection. The theoretical resolution of the system is 1.5cm, and it has been verified in experiments that a resolution of 1.4cm has been achieved. However, the carrier band frequency limits the resolution of the chaotic radar system, which is not conducive to high-precision target resolution and detection.

[0004] The LiDAR system uses a higher carrier frequency to detect targets. Due to its richer spectrum resources, it can achieve higher sensing resolution and ranging capabilities. In 2023, Ruixuan Chen et al. used the nonlinear characteristics of microrings to generate a chaotic comb to realize a parallel LiDAR system. The resolution of a single chaotic comb tooth is 2.25 cm. The system achieved a ranging accuracy of 2 mm and a range of 5 mm in the experiment. -1 However, radar systems based on optical frequency bands are particularly sensitive to environmental factors, especially scattering from aerosols such as smoke or dust. In this case, the THz band provides a compromise between carrier frequency and bandwidth resources, and is a promising alternative that can achieve high-precision sensing and unambiguous ranging under strong environmental interference. Summary of the invention

[0005] In view of the above, the purpose of the present invention is to provide a terahertz radar system based on chaotic signals, which uses a flexible optical architecture to generate terahertz chaotic signals as radar detection signals, which can improve radar detection accuracy, solve the problem of radar detection ambiguity, and improve the safety and anti-interference of the radar system.

[0006] In order to achieve the above-mentioned invention object, the technical solution provided by the present invention is as follows:

[0007] A terahertz radar system based on chaotic signals provided by an embodiment of the present invention includes: a signal transmission link and a signal receiving link;

[0008] The signal transmission link is used to generate and transmit terahertz chaotic signals to the target object;

[0009] The signal receiving link is used to receive the reflected signal of the terahertz chaotic signal acting on the target object and process it to obtain the perception information.

[0010] Preferably, the signal transmission link comprises: a multi-wavelength coherent light source module and a chaotic signal transmission module;

[0011] The multi-wavelength coherent light source module is used to generate two coherent optical carriers;

[0012] The chaotic signal transmitting module is used to generate and transmit terahertz chaotic signals based on two coherent optical carriers.

[0013] Preferably, the multi-wavelength coherent light source module uses an electro-optic modulator or an electro-optic resonant cavity to generate an optical frequency comb, and then two optical carriers are filtered out in an input filter, and the frequency difference between the two optical carriers is equal to the terahertz frequency.

[0014] Preferably, the chaotic signal transmitting module comprises: a first optical amplifier, a first polarization controller, a chaotic signal generating module, a first adjustable attenuator, a first optical coupler, a second optical amplifier, a second polarization controller, a second adjustable attenuator and a terahertz signal transmitter;

[0015] The first optical amplifier is used for receiving and amplifying the first optical carrier of the two coherent optical carriers;

[0016] The first polarization controller is used to adjust the polarization state of the amplified first optical carrier beam;

[0017] The chaotic signal generating module is used to generate a chaotic signal in the optical domain using the first optical carrier beam after the polarization state is adjusted;

[0018] The first adjustable attenuator is used to use the second optical carrier of the two coherent optical carriers as an optical local oscillator signal, and adjust the optical power of the optical local oscillator signal to match the power of the chaotic signal output by the chaotic signal generating module;

[0019] The first optical coupler is used to couple the chaotic signal output by the chaotic signal generating module and the optical local oscillator signal after the optical power is adjusted output by the first adjustable attenuator to obtain a coupling signal;

[0020] The second optical amplifier is used for amplifying the coupled signal;

[0021] The second polarization controller is used to adjust the polarization state of the amplified coupled signal;

[0022] The second adjustable attenuator is used to adjust the optical power of the coupled signal after the polarization state is adjusted;

[0023] The terahertz signal transmitter is used to generate and transmit a terahertz chaotic signal by using a coupled signal after optical power adjustment through beat frequency.

[0024] Preferably, the signal receiving link comprises: a terahertz signal receiver, a signal processing module and a first photoelectric converter;

[0025] The terahertz signal receiver is used to receive the reflected signal of the terahertz chaotic signal acting on the target object and obtain the intermediate frequency signal through down-conversion;

[0026] The first photoelectric converter is used to receive the chaotic signal generated by the chaotic signal generating module and convert it into an electrical chaotic signal and then input it into the signal processing module as a reference signal;

[0027] The signal processing module is used to perform signal processing based on the intermediate frequency signal and the reference signal to obtain perception information.

[0028] Preferably, the chaotic signal generating module generates a chaotic signal in the optical domain using a nonlinear optoelectronic physical device, wherein the nonlinear optoelectronic physical device includes a laser, a Mach-Zehnder modulator or a Mach-Zehnder interferometer.

[0029] Preferably, the terahertz signal transmitter comprises: a single-row carrier photodetector or a PIN-type photodetector.

[0030] Preferably, the first optical amplifier or the second optical amplifier comprises: a semiconductor optical amplifier or an erbium-doped fiber amplifier.

[0031] Preferably, the terahertz signal receiver comprises: a subharmonic mixer, a photoconductive antenna, a Schottky barrier diode or a quantum well photodetector.

[0032] Preferably, the signal receiving link processes the reflected signal through a range-Doppler algorithm, a back-projection algorithm or a compressed sensing algorithm and obtains sensing information including the distance, speed, and two-dimensional or three-dimensional information of the target object.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention realizes terahertz radar based on chaotic signals, which can effectively improve the anti-interference and safety performance of the radar system;

[0035] (2) The present invention realizes terahertz radar based on chaotic signals, which can effectively avoid the radar detection ambiguity problem and improve the radar detection resolution;

[0036] (3) The present invention realizes terahertz radar based on chaotic signals, which has excellent autocorrelation characteristics and improves radar detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 is a schematic structural diagram of a terahertz radar system based on chaotic signals provided by an embodiment of the present invention;

[0039] Figure 2 is a schematic structural diagram of a multi-wavelength coherent light source module provided by an embodiment of the present invention;

[0040] Figure 3 It is a structural schematic diagram of a chaotic signal generating module provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] To make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0042] The inventive concept of the present invention is: in response to the technical problems of detection ambiguity, low security and anti-interference ability in existing terahertz radars, the embodiments of the present invention provide a terahertz radar system based on chaotic signals, which uses a flexible optical architecture to generate terahertz chaotic signals as radar detection signals, which can improve radar detection accuracy, solve the problem of radar detection ambiguity, and at the same time improve the security and anti-interference ability of the radar system.

[0043] Figure 1 FIG. 1 is a schematic diagram of the structure of a terahertz radar system based on chaotic signals provided by an embodiment of the present invention. Figure 1 As shown, an embodiment provides a terahertz radar system based on a chaotic signal, comprising: a signal transmitting link and a signal receiving link, wherein the signal transmitting link is used to generate and transmit a terahertz chaotic signal to a target object, and the signal receiving link is used to receive a reflected signal of the terahertz chaotic signal acting on the target object and process it to obtain perception information.

[0044] Specifically, the signal transmission link includes: a multi-wavelength coherent light source module and a chaotic signal transmission module. The multi-wavelength coherent light source module is used to generate two coherent optical carriers, and the chaotic signal transmission module is used to generate and transmit terahertz chaotic signals based on the two coherent optical carriers.

[0045] In the embodiment, the multi-wavelength coherent light source module uses an electro-optic modulator or an electro-optic resonant cavity to generate an optical frequency comb, and then two optical carriers are filtered out in the input filter, and the frequency difference between the two optical carriers is equal to the terahertz frequency. The filter includes a passive filter or an active filter. Figure 2As shown, an embodiment provides a multi-wavelength coherent light source module, including: a tunable laser, a third polarization controller, a phase modulator, a signal generator, a first electrical amplifier and a tunable wavelength selective switch. Among them, a seed light signal is generated by a tunable laser, and the tunable laser includes an external cavity laser, a DFB laser, a DBR laser or a single longitudinal mode solid laser. The seed light signal is adjusted to its polarization state by the third polarization controller to maximize the optical power of the output phase modulator, and then enters the phase modulator. At the same time, a radio frequency signal is generated by a signal generator and amplified by the first electrical amplifier and input to the phase modulator. Finally, the phase modulator performs phase modulation based on the seed light signal and the radio frequency signal to obtain an optical frequency comb and input it into the tunable wavelength selective switch (an active filter). The tunable wavelength selective switch is used to filter the optical frequency comb to output two coherent optical carriers, and the frequency difference between the two optical carriers is the terahertz carrier frequency to be generated.

[0046] In an embodiment, the chaotic signal transmitting module includes: a first optical amplifier, a first polarization controller, a chaotic signal generating module, a first adjustable attenuator, a first optical coupler, a second optical amplifier, a second polarization controller, a second adjustable attenuator and a terahertz signal transmitter. Among them, the first optical amplifier receives and amplifies the first optical carrier of the two coherent optical carriers, and then adjusts the polarization state of the first optical carrier through the first polarization controller so that the polarization of the input optical signal is aligned with the polarization principal axis of the polarization sensitive device in the chaotic signal generating module, and then inputs the chaotic signal generating module, and generates a chaotic signal in the optical domain through the chaotic signal generating module. At the same time, the second optical carrier of the two coherent optical carriers is used as an optical local oscillator signal through the first adjustable attenuator, and the optical power of the optical local oscillator signal is adjusted to match the chaotic signal power output by the chaotic signal generating module. Then, the chaotic signal output by the chaotic signal generating module and the optical local oscillator signal after the optical power adjustment output by the first adjustable attenuator are coupled by the first optical coupler to obtain a coupled signal, and then the coupled signal is amplified by the second optical amplifier, and then the polarization state of the amplified coupled signal is adjusted by the second polarization controller to maximize the output power of the terahertz signal transmitter, and then the coupled signal after the polarization state adjustment is adjusted by the second adjustable attenuator to input the optical power of the terahertz signal transmitter, and finally the terahertz signal transmitter uses the coupled signal after the optical power adjustment to generate a terahertz chaotic signal through the beat frequency and transmit it to the free space. Among them, the terahertz signal transmitter includes: a single-line carrier photodetector or a PIN-type photodetector, and the first optical amplifier or the second optical amplifier includes: a semiconductor optical amplifier or an erbium-doped fiber amplifier.

[0047] In the embodiment, the chaotic signal generating module generates a chaotic signal in the optical domain using the nonlinear characteristics of a nonlinear optoelectronic physical device. The nonlinear optoelectronic physical device includes a laser, a Mach-Zehnder modulator or a Mach-Zehnder interferometer, wherein the generation method of generating a chaotic signal in the optical domain using the nonlinearity of the laser includes optical feedback, optical injection or optoelectronic feedback. Figure 3 As shown, an embodiment provides a chaotic signal generating module, including: an intensity modulator, a second optical coupler, an optical fiber delay line, a second photoelectric converter, a third optical coupler and a second electrical amplifier. The intensity modulator is used as a key component to excite chaotic output to realize nonlinear photoelectric conversion, and the chaotic signal output by the intensity modulator is divided into two paths by the second optical coupler, one path is sent to the optical fiber delay line as a feedback signal, and the other path is sent to the first optical coupler as a module output signal. A loop delay is introduced through the optical delay line, and the chaotic signal is divided into two paths through the third optical coupler, one path is input into the first photoelectric converter as a reference signal, and the other path is input into the second photoelectric converter as a feedback signal, and the feedback signal is converted into an electrical signal by the second photoelectric converter. Finally, the feedback electrical signal is amplified by the second electrical amplifier to excite sufficient nonlinearity of the intensity modulator.

[0048] Specifically, the signal receiving link includes a terahertz signal receiver, a signal processing module and a first photoelectric converter. The terahertz signal receiver receives the reflected signal of the terahertz chaotic signal acting on the target object and obtains the intermediate frequency signal through down-conversion. The terahertz signal receiver includes: a subharmonic mixer, a photoconductive antenna, a Schottky barrier diode or a quantum well photodetector. At the same time, the chaotic signal generated by the chaotic signal generating module is received by the first photoelectric converter and converted into an electrical chaotic signal and then input into the signal processing module as a reference signal. Finally, the signal processing module performs signal processing based on the intermediate frequency signal and the reference signal to obtain the perception information, wherein, when the signal processing is performed based on the received intermediate frequency signal and combined with the reference signal output by the signal generating module, the distance, speed and two-dimensional or three-dimensional information of the target object are detected through the distance-Doppler algorithm, the back projection algorithm or the compressed sensing algorithm.

[0049] In summary, in the terahertz radar system based on chaotic signals provided in the above embodiments, the optical chaotic signal generated by the chaotic signal generating module is coupled with the local oscillator signal, and the center frequency difference of the two signals is equal to the center frequency of the terahertz signal to be generated. The coupled optical signal is optically heterodyned by the terahertz signal transmitter to obtain a terahertz chaotic radar signal and radiate it into free space. The optical heterodyne system architecture can generate a terahertz chaotic signal with large bandwidth and low harmonic interference. By combining the optical chaotic signal with the photonic terahertz radar system, the radar detection accuracy can be improved, the radar detection ambiguity problem can be solved, and the safety and anti-interference of the radar system can be improved.

[0050] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A terahertz radar system based on chaotic signals, characterized in that: include: Signal transmission link and signal receiving link; The signal transmission link is used to generate and transmit a terahertz chaotic signal to a target object, and the signal transmission link includes: a multi-wavelength coherent light source module and a chaotic signal transmission module, wherein the multi-wavelength coherent light source module is used to generate two coherent optical carriers, and the chaotic signal transmission module is used to generate and transmit a terahertz chaotic signal based on the two coherent optical carriers; the chaotic signal transmission module includes: a first optical amplifier, a first polarization controller, a chaotic signal generation module, a first adjustable attenuator, a first optical coupler, a second optical amplifier, a second polarization controller, a second adjustable attenuator and a terahertz signal transmitter, wherein the first optical amplifier is used to receive and amplify the first optical carrier of the two coherent optical carriers, the first polarization controller is used to adjust the polarization state of the amplified first optical carrier, and the chaotic signal generation module is used to generate and transmit a terahertz chaotic signal based on the two coherent optical carriers. The module is used to generate a chaotic signal in the optical domain using the first optical carrier after polarization state adjustment, the first adjustable attenuator is used to use the second optical carrier of the two coherent optical carriers as an optical local oscillator signal and adjust the optical power of the optical local oscillator signal to match the chaotic signal power output by the chaotic signal generating module, the first optical coupler is used to couple the chaotic signal output by the chaotic signal generating module and the optical local oscillator signal after optical power adjustment output by the first adjustable attenuator to obtain a coupled signal, the second optical amplifier is used to amplify the coupled signal, the second polarization controller is used to adjust the polarization state of the amplified coupled signal, the second adjustable attenuator is used to adjust the optical power of the coupled signal after polarization state adjustment, and the terahertz signal transmitter is used to generate a terahertz chaotic signal through beat frequency using the coupled signal after optical power adjustment and transmit it; The signal receiving link is used to receive the reflected signal of the terahertz chaotic signal acting on the target object and process it to obtain the perception information. The signal receiving link includes: a terahertz signal receiver, a signal processing module and a first photoelectric converter, wherein the terahertz signal receiver is used to receive the reflected signal of the terahertz chaotic signal acting on the target object and obtain the intermediate frequency signal through down-conversion, the first photoelectric converter is used to receive the chaotic signal generated by the chaotic signal generating module and convert it into an electrical chaotic signal and then input it into the signal processing module as a reference signal, and the signal processing module is used to perform signal processing based on the intermediate frequency signal and the reference signal to obtain the perception information.

2. The terahertz radar system based on chaotic signals according to claim 1, characterized in that: The multi-wavelength coherent light source module uses an electro-optic modulator or an electro-optic resonant cavity to generate an optical frequency comb, and then inputs it into a filter to filter out two optical carriers, and the frequency difference between the two optical carriers is equal to the terahertz frequency.

3. The terahertz radar system based on chaotic signals according to claim 1, characterized in that: The chaotic signal generating module generates chaotic signals in the optical domain by using nonlinear optoelectronic physical devices, wherein the nonlinear optoelectronic physical devices include lasers, Mach-Zehnder modulators or Mach-Zehnder interferometers.

4. The terahertz radar system based on chaotic signals according to claim 1, characterized in that: The terahertz signal transmitter includes: a single-line carrier photodetector or a PIN-type photodetector.

5. The terahertz radar system based on chaotic signals according to claim 1, characterized in that: The first optical amplifier or the second optical amplifier includes: a semiconductor optical amplifier or an erbium-doped fiber amplifier.

6. The terahertz radar system based on chaotic signals according to claim 1, characterized in that: Terahertz signal receivers include: subharmonic mixers, photoconductive antennas, Schottky barrier diodes or quantum well photodetectors.

7. The terahertz radar system based on chaotic signals according to claim 1, characterized in that: The signal receiving link processes the reflected signal through a range-Doppler algorithm, a back-projection algorithm or a compressed sensing algorithm and obtains sensing information including the distance, speed, and two-dimensional or three-dimensional information of the target object.

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