A signal detection system

Abstract

This application discloses a signal detection system, comprising: a frequency estimation device and a signal detection device; the output terminal of the frequency estimation device is connected to the input terminal of the signal detection device. The system can generate a chaotic photoelectric oscillator radio frequency signal by estimating the frequency of the incident signal and the optical carrier signal based on environmental conditions. Then, the chaotic photoelectric oscillator radio frequency signal is used to detect the target signal (i.e., a weak microwave photon signal). Therefore, the system can achieve the reception of weak signals within a large dynamic bandwidth, overcoming the shortcomings of traditional signal detection methods, such as narrow operating bandwidth and low detection sensitivity.

Description

Technical Field

[0001] This application relates to the field of detection technology, and in particular to a signal detection system. Background Technology

[0002] At present, radar wave reception is mostly based on coherent detection principle. The strength of radar signals is generally low, or even submerged in noise. Traditional electronic signal amplification methods are difficult to overcome the bottlenecks in devices, with narrow operating bandwidth and high noise degradation, making it difficult to meet the needs of modern battlefield. The range and effectiveness of radar jammers are difficult to improve significantly.

[0003] Current methods for weak signal detection primarily involve time-domain detection, frequency-domain detection, and time-frequency analysis. These methods mainly employ electronic amplification of the signal, followed by different filtering techniques in the time and frequency domains. The core of traditional electronic detection methods is amplification followed by filtering, and finally coherent detection using beat frequency modulation. This approach struggles to achieve high sensitivity over a wide dynamic range, hindering the detection of weak radar signals in various signal formats common in modern applications. For example, current signal amplification methods utilize multi-stage electronic amplifiers, leading to a significant increase in white noise. Furthermore, coherent detection methods require pre-generating multiple radio frequency signals for blind testing, making detection over a wide dynamic range impossible. Summary of the Invention

[0004] This application provides a signal detection system that can expand the bandwidth of the target signal (i.e., weak signal), reduce noise interference during signal processing, receive weak signals within a larger dynamic bandwidth range, and improve the shortcomings of traditional signal detection methods, such as narrow working bandwidth and low detection sensitivity.

[0005] In a first aspect, this application provides a signal detection system, the system comprising: a frequency prediction device and a signal detection device; the output terminal of the frequency prediction device is connected to the input terminal of the signal detection device;

[0006] The frequency estimation device is used to generate several optical carrier signals; based on the several radio frequency signals, the frequency of the incident signal is estimated; and the estimated frequency of the incident signal is output through the output terminal.

[0007] The signal detection device is used to acquire the estimated frequency of the incident signal through the input terminal, and to generate an optical carrier signal; to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the optical carrier signal; and to detect the target signal using the chaotic photoelectric oscillator radio frequency signal.

[0008] Optionally, the frequency prediction device includes a laser, a radio frequency signal generation unit, and a digital-to-analog converter; the signal output terminal of the laser is connected to the input terminal of the radio frequency signal generation unit, the output terminal of the radio frequency signal generation unit is connected to the input terminal of the digital-to-analog converter, and the output terminal of the digital-to-analog converter is connected to the input terminal of the signal detection device.

[0009] The laser is used to generate several optical carrier signals;

[0010] The radio frequency signal generation unit is used to determine several radio frequency signals based on the several optical carrier signals;

[0011] The digital-to-analog converter is used to estimate the frequency of the incident signal based on the plurality of radio frequency signals.

[0012] Optionally, the laser includes two lasers, each of which generates an optical carrier signal.

[0013] Optionally, the radio frequency signal generation unit includes: a wavelength division multiplexer, a polarization controller, a Mach-Zehnder modulator, a filter, a de-wavelength division multiplexer, and a photodetector; the input terminal of the wavelength division multiplexer is connected to the signal output terminal of the laser, the output terminal of the wavelength division multiplexer is connected to the input terminal of the polarization controller, the output terminal of the polarization controller is connected to the input terminal of the Mach-Zehnder modulator, the output terminal of the Mach-Zehnder modulator is connected to the input terminal of the filter, the output terminal of the filter is connected to the input terminal of the de-wavelength division multiplexer, the output terminal of the de-wavelength division multiplexer is connected to the input terminal of the photodetector, and the output terminal of the photodetector is connected to the input terminal of the signal detection device.

[0014] The wavelength division multiplexer is used to mix two optical carrier signals to obtain one optical carrier signal;

[0015] The polarization controller is used to adjust the polarization state of the optical carrier signal to obtain a polarization-adjusted optical carrier signal.

[0016] A Mach-Zehnder modulator is used to modulate the polarization-adjusted optical carrier signal to obtain a modulated optical signal.

[0017] The filter is used to filter the modulated optical signal to obtain a carrier-suppressed optical signal;

[0018] The dewavelength division multiplexer is used to perform dewavelength division multiplexing processing on the carrier-suppressed optical signal to obtain two optical signals.

[0019] The photodetector is used to perform beat frequency processing on the two light signals to obtain two radio frequency signals.

[0020] Optionally, the photodetector includes two photodetectors, each of which is used to receive a beam of light signal, perform beat frequency processing on the beam of light signal, and obtain the radio frequency signal corresponding to the beam of light signal.

[0021] Optionally, the signal detection device includes: a laser, a signal generation unit, and a signal detection unit; the output terminal of the laser is connected to the input terminal of the signal generation unit, and the input terminal of the signal generation unit is connected to the output terminal of the frequency prediction device; the output terminal of the signal generation unit is connected to the input terminal of the signal detection unit; and the output terminal of the signal detection unit is connected to the input terminal of the signal generation unit.

[0022] The laser is used to generate an optical carrier signal;

[0023] The signal generation unit is used to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the optical carrier signal.

[0024] The signal detection unit is used to detect the target signal using the radio frequency signal of the chaotic photoelectric oscillator.

[0025] Optionally, the signal generation unit includes: a polarization controller, a Mach-Zehnder modulator, a single-mode fiber, and a tunable fiber Bragg grating; the input end of the polarization controller is connected to the signal output end of the laser, the output end of the polarization controller is connected to the input end of the Mach-Zehnder modulator, the output end of the Mach-Zehnder modulator is connected to the input end of the single-mode fiber, and the output end of the single-mode fiber is connected to the input end of the tunable fiber Bragg grating;

[0026] The polarization controller is used to adjust the polarization state of the optical carrier signal to obtain a polarization-adjusted optical carrier signal.

[0027] The Mach-Zehnder modulator is used to modulate the polarization-adjusted optical carrier signal to obtain a modulated optical signal.

[0028] The single-mode optical fiber is used to delay the modulated optical signal to obtain a delayed optical signal.

[0029] The tunable fiber Bragg grating is used to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the delayed optical signal.

[0030] Optionally, the signal detection unit includes: a coupler, a spectrum analyzer, a photodetector, a frequency-adjustable radio frequency amplifier, a radio frequency beam splitter, a radio frequency analyzer, and a low-noise amplifier;

[0031] The input terminal of the coupler is connected to the output terminal of the tunable fiber Bragg grating, the output terminal of the coupler is connected to the input terminal of the spectrometer, the output terminal of the coupler is connected to the input terminal of the photodetector, the output terminal of the photodetector is connected to the input terminal of the frequency-tunable radio frequency amplifier, the output terminal of the frequency-tunable radio frequency amplifier is connected to the input terminal of the radio frequency beam splitter, the output terminal of the radio frequency beam splitter is connected to the input terminal of the radio frequency analyzer, the output terminal of the radio frequency beam splitter is connected to the input terminal of the low-noise amplifier, and the output terminal of the low-noise amplifier is connected to the input terminal of the Mach-Zehnder modulator.

[0032] The coupler is used to split the chaotic photoelectric oscillator radio frequency signal into two chaotic photoelectric oscillator radio frequency signals.

[0033] The spectrum analyzer is used to analyze the signal state of the radio frequency signal of the chaotic photoelectric oscillator;

[0034] The photodetector is used to perform beat frequency processing on the radio frequency signal of the chaotic photoelectric oscillator to obtain a radio frequency signal;

[0035] The frequency-adjustable radio frequency amplifier is used to amplify the radio frequency signal to obtain an amplified radio frequency signal;

[0036] The radio frequency beam splitter is used to split the amplified radio frequency signal into two beams of the amplified radio frequency signal;

[0037] The radio frequency analyzer is used to observe the amplified radio frequency signal in order to obtain the target signal;

[0038] The low-noise amplifier is used to amplify the target signal in the amplified radio frequency signal.

[0039] Optionally, the tunable fiber Bragg grating further includes a reflector. The delayed optical signal is input to the input end of the tunable fiber Bragg grating. The delayed optical signal enters from the reflector. After the delayed optical signal is reflected by the fiber Bragg grating according to the estimated frequency of the incident signal, a chaotic photoelectric oscillator radio frequency signal is obtained. The chaotic photoelectric oscillator radio frequency signal enters the output end from the reflector.

[0040] Optionally, the tunable fiber Bragg grating is provided with a knob. When the knob is adjusted, the length of the grating changes, and the wavelength of the reflected light also changes accordingly.

[0041] As can be seen from the above technical solution, this application provides a signal detection system, the system comprising: a frequency prediction device and a signal detection device; the output terminal of the frequency prediction device is connected to the input terminal of the signal detection device; the frequency prediction device is used to generate a plurality of optical carrier signals; determine a plurality of radio frequency signals based on the plurality of optical carrier signals; obtain an estimated frequency of an incident signal based on the plurality of radio frequency signals; output the estimated frequency of the incident signal through the output terminal; the signal detection device is used to acquire the estimated frequency of the incident signal through the input terminal, and to generate optical carrier signals; generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the optical carrier signals; and detect a target signal using the chaotic photoelectric oscillator radio frequency signal. This embodiment can generate a chaotic photoelectric oscillator radio frequency signal by estimating the frequency of the incident signal and the optical carrier signal based on the environment. Then, the target signal (i.e., the weak microwave photon signal) can be detected using the chaotic photoelectric oscillator radio frequency signal. It can be seen that this embodiment can achieve the reception of the target signal (i.e., the weak signal) within a large dynamic bandwidth range, which improves the shortcomings of traditional signal detection methods, such as narrow working bandwidth and low detection sensitivity.

[0042] The further effects of the aforementioned non-conventional preferred method will be explained below in conjunction with specific embodiments. Attached Figure Description

[0043] To more clearly illustrate the embodiments of this application or the existing technical solutions, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the system architecture of a frequency prediction device in a signal detection system according to this application;

[0045] Figure 2 This is a schematic diagram of the system architecture of a signal detection device in a signal detection system according to this application. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] The various non-limiting embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0048] See Figure 1 and Figure 2 This document illustrates a signal detection system according to an embodiment of the present application.

[0049] The signal detection system includes a frequency prediction device and a signal detection device. The output of the frequency prediction device is connected to the input of the signal detection device.

[0050] The frequency prediction device is used to generate several optical carrier signals; determine several radio frequency signals based on the several optical carrier signals; obtain an estimated frequency of the incident signal based on the several radio frequency signals; and output the estimated frequency of the incident signal through the output terminal. It is understood that the frequency prediction device can predict the frequency value of radio frequency signals in the environment, controlling its frequency prediction error within a range of 300MHz.

[0051] like Figure 1 As shown, the frequency prediction device includes a laser, a radio frequency signal generation unit, and a digital-to-analog converter. The signal output terminal of the laser is connected to the input terminal of the radio frequency signal generation unit, the output terminal of the radio frequency signal generation unit is connected to the input terminal of the digital-to-analog converter, and the output terminal of the digital-to-analog converter is connected to the input terminal of the signal detection device.

[0052] The laser is used to generate several optical carrier signals. For example... Figure 1 As shown, the laser may include two lasers, each of which generates an optical carrier signal.

[0053] The radio frequency signal generation unit is used to determine several radio frequency signals based on the several optical carrier signals. For example... Figure 2 As shown, the radio frequency signal generation unit includes: a wavelength division multiplexer, a polarization controller, a Mach-Zehnder modulator, a filter, a demultiplexer, and a photodetector; the input terminal of the wavelength division multiplexer is connected to the signal output terminal of the laser, the output terminal of the wavelength division multiplexer is connected to the input terminal of the polarization controller, the output terminal of the polarization controller is connected to the input terminal of the Mach-Zehnder modulator, the output terminal of the Mach-Zehnder modulator is connected to the input terminal of the filter, the output terminal of the filter is connected to the input terminal of the demultiplexer, the output terminal of the demultiplexer is connected to the input terminal of the photodetector, and the output terminal of the photodetector is connected to the input terminal of the signal detection device.

[0054] The wavelength division multiplexer is used to mix two optical carrier signals to obtain a single optical carrier signal. The polarization controller is used to adjust the polarization state of the optical carrier signal to obtain a polarization-adjusted optical carrier signal.

[0055] A Mach-Zehnder modulator is used to modulate the polarization-adjusted optical carrier signal to obtain a modulated optical signal.

[0056] The filter is used to filter the modulated optical signal to obtain a carrier-suppressed optical signal.

[0057] The dewavelength division multiplexer is used to perform dewavelength division multiplexing processing on the carrier-suppressed optical signal to obtain two optical signals.

[0058] The photodetector is used to perform beat frequency processing on the two light signals to obtain two radio frequency signals. For example... Figure 1 As shown, the photodetector includes two photodetectors, each of which is used to receive a beam of light signal, perform beat frequency processing on the beam of light signal, and obtain the radio frequency signal corresponding to the beam of light signal.

[0059] The digital-to-analog converter is used to estimate the frequency of the incident signal based on the plurality of radio frequency signals.

[0060] It is understandable that the frequency prediction device employs a scheme for instantaneous measurement of frequency-optical power radio frequency signals using a dual-light source, achieving the effect of instantaneous microwave signal measurement, such as... Figure 1 As shown, two optical carrier signals emitted by two semiconductor lasers are optically multiplexed and mixed by a wavelength division multiplexer to obtain a single optical carrier signal. This single optical carrier signal is then polarized by a polarization controller (PC) and input to a Mach-Zehnder modulator. By adjusting the bias voltage of the Mach-Zehnder modulator, it can be made to operate at its minimum operating point, thus maximally suppressing the optical carrier in the modulated optical signal output by the Mach-Zehnder modulator. The modulated optical signal is then input into a filter with a sinusoidal spectral response to obtain a carrier-suppressed optical signal. The wavelength of the modulated optical signal can include two optical channels, and the wavelengths of the two optical channels can be aligned with the peaks and troughs of the filter, respectively. The carrier-suppressed optical signal is separated into two optical channels by a demultiplexer. The two optical channels are then beat by two photodetectors (such as low-frequency photodetectors) to obtain two radio frequency signals. The detected radio frequency signals are converted from analog to digital by a digital-to-analog converter and compared. By comparing the ratio of the two radio frequency signals and combining the response curve of the filter, the frequency of the incident signal can be estimated. That is, the frequency of the incident signal can be estimated by using several radio frequency signals and the response curve of the filter.

[0061] The signal detection device is used to acquire the estimated frequency of the incident signal through the input terminal, and to generate an optical carrier signal; to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the optical carrier signal; and to detect the target signal using the chaotic photoelectric oscillator radio frequency signal.

[0062] like Figure 2 As shown, the signal detection device includes a laser, a signal generation unit, and a signal detection unit. The output terminal of the laser is connected to the input terminal of the signal generation unit, and the input terminal of the signal generation unit is connected to the output terminal of the frequency prediction device; the output terminal of the signal generation unit is connected to the input terminal of the signal detection unit; and the output terminal of the signal detection unit is connected to the input terminal of the signal generation unit.

[0063] The laser is used to generate an optical carrier signal.

[0064] The signal generation unit is used to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the optical carrier signal. Figure 2 As shown, the signal generation unit includes: a polarization controller, a Mach-Zehnder modulator, a single-mode fiber, and a tunable fiber Bragg grating; the input end of the polarization controller is connected to the signal output end of the laser, the output end of the polarization controller is connected to the input end of the Mach-Zehnder modulator, the output end of the Mach-Zehnder modulator is connected to the input end of the single-mode fiber, and the output end of the single-mode fiber is connected to the input end of the tunable fiber Bragg grating.

[0065] The polarization controller is used to adjust the polarization state of the optical carrier signal to obtain a polarization-adjusted optical carrier signal.

[0066] The Mach-Zehnder modulator is used to modulate the polarization-adjusted optical carrier signal to obtain a modulated optical signal.

[0067] The single-mode optical fiber is used to delay the modulated optical signal to obtain a delayed optical signal.

[0068] The tunable fiber Bragg grating is used to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the delayed optical signal. The tunable fiber Bragg grating also includes a reflector and an input terminal (i.e.,...) Figure 2 The delayed optical signal is input from port 1 in the middle, and the delayed optical signal is received from the reflecting end (i.e., port 1). Figure 2The signal enters from port 2 of the optical fiber. Based on the estimated frequency of the incident signal, the delayed optical signal is reflected using a fiber optic Lagrange grating to obtain a chaotic photoelectric oscillator radio frequency signal. This chaotic photoelectric oscillator radio frequency signal enters the output port (i.e., port 2) from the reflection end. Figure 2 (3 ports in the diagram). In one implementation, the tunable fiber Bragg grating is provided with a knob. When the knob is adjusted, the length of the grating changes, and the wavelength of the reflected light also changes accordingly.

[0069] The signal detection unit is used to detect the target signal (i.e., weak signal) using the radio frequency signal of the chaotic photoelectric oscillator.

[0070] like Figure 2 As shown, the signal detection unit includes: a coupler, a spectrum analyzer, a photodetector, a frequency-adjustable radio frequency amplifier, a radio frequency beam splitter, a radio frequency analyzer, and a low-noise amplifier.

[0071] The input terminal of the coupler is connected to the output terminal of the tunable fiber Bragg grating, the output terminal of the coupler is connected to the input terminal of the spectrometer, the output terminal of the coupler is connected to the input terminal of the photodetector, the output terminal of the photodetector is connected to the input terminal of the frequency-tunable radio frequency amplifier, the output terminal of the frequency-tunable radio frequency amplifier is connected to the input terminal of the radio frequency beam splitter, the output terminal of the radio frequency beam splitter is connected to the input terminal of the radio frequency analyzer, the output terminal of the radio frequency beam splitter is connected to the input terminal of the low-noise amplifier, and the output terminal of the low-noise amplifier is connected to the input terminal of the Mach-Zehnder modulator.

[0072] The coupler is used to split the chaotic photoelectric oscillator radio frequency signal into two chaotic photoelectric oscillator radio frequency signals.

[0073] The spectrum analyzer is used to analyze the signal state of the radio frequency signal of the chaotic photoelectric oscillator.

[0074] The photodetector is used to perform beat frequency processing on the radio frequency signal of the chaotic photoelectric oscillator to obtain a radio frequency signal.

[0075] The frequency-adjustable radio frequency amplifier is used to amplify the radio frequency signal to obtain an amplified radio frequency signal.

[0076] The radio frequency beam splitter is used to split the amplified radio frequency signal into two beams.

[0077] The radio frequency analyzer is used to observe the amplified radio frequency signal in order to obtain the target signal.

[0078] The low-noise amplifier is used to amplify the target signal in the amplified radio frequency signal.

[0079] The signal detection device uses a method of constructing an optoelectronic oscillation ring cavity to generate a chaotic optoelectronic oscillator (OEO) radio frequency (RF) signal. The chaotic state of the OEO is a critical state between oscillation start-up and non-oscillation, meaning the open-loop gain in the OEO is close to 1, and the vibration mode is about to appear. The chaotic OEO is a nonlinear delayed feedback loop. When an RF signal is injected into the OEO, the gain within the optoelectronic oscillation ring cavity increases, the start-up frequency is locked by the injected signal, and energy is concentrated at the center frequency of the start-up, thus amplifying weak signals.

[0080] Signal detection devices such as Figure 2 As shown, the laser emits an optical carrier whose polarization direction is adjusted by a polarization controller (i.e., the polarization state of the optical carrier signal is adjusted to obtain a polarization-adjusted optical carrier signal). The polarization-adjusted optical carrier signal is then input to a Mach-Zehnder modulator. The Mach-Zehnder modulator outputs a modulated optical signal, which is delayed by a long single-mode fiber to obtain a delayed optical signal. The chaotic photoelectric oscillator radio frequency signal is split into two chaotic photoelectric oscillator radio frequency signals (i.e., two chaotic photoelectric oscillator radio frequency signals) by a coupler (i.e., an optical beam splitter). One signal is input to a spectrum analyzer so that the spectrum analyzer can analyze the chaotic optical signal state of the chaotic photoelectric oscillator radio frequency signal. The other signal is connected to a photodetector, which can beat the chaotic photoelectric oscillator radio frequency signal to generate a radio frequency signal. The generated radio frequency (RF) signal is amplified by a gain-adjustable RF amplifier (i.e., a frequency-adjustable RF amplifier) ​​to obtain an amplified RF signal. An RF beam splitter then splits this amplified RF signal into two paths. One path is input to an RF analyzer to observe the electrically chaotic state of the amplified RF signal, which helps adjust the bias voltage of the Mach-Zehnder modulator and the gain of the frequency-adjustable RF amplifier. The other path is fed back into the Mach-Zehnder modulator after passing through a low-noise amplifier, thus completing the closed-loop link. Since the chaotic state of the photoelectric oscillator RF signal is a nonlinear MZM modulation state, high flatness and frequency response bandwidth are required, necessitating relatively flatness in the frequency-adjustable RF amplifier within the link.

[0081] The signal detection device achieves the reception and amplification of weak radar signals through injection lock-in effect, and uses small-signal receiver frequency tuning technology to increase the bandwidth range of the detectable signal. Because the frequency response of tunable fiber Bragg gratings in chaotic states is greatly affected by the bandwidth and flatness of each component in the system, it is difficult to widen the operating bandwidth of tunable fiber Bragg gratings; the resulting chaotic optoelectronic oscillator RF signal is typically 300-800MHz. If the system is to be used in an electromagnetic environment with a wider frequency range, a tunable fiber Bragg grating with adjustable bandwidth can be designed. Combined with a frequency instantaneous measurement scheme, the frequency of the incident signal in the environment is first estimated, and then a tunable fiber Bragg grating with a bandwidth exceeding 500MHz is formed in the loop cavity (i.e., composed of a frequency prediction device and a signal detection device), thereby achieving the function of receiving and amplifying target signals (i.e., weak signals) over a wider frequency range. Combining a frequency-tunable optoelectronic oscillator (OEO) scheme, a chaotic OEO operating frequency band tuning scheme is proposed. Utilizing the characteristic that the center frequency of the reflected light from a tunable fiber Bragg grating varies with its length, a frequency-tunable chaotic OEO RF signal is generated in the loop. The principle of the scheme is as follows: Figure 2 As shown.

[0082] The laser emits an optical carrier signal that passes through a polarization controller, a Mach-Zehnder modulator, a single-mode fiber, and a tunable fiber Bragg grating. The radio frequency chaotic signal fed back in the loop is modulated onto the optical carrier to obtain a chaotic photoelectric oscillator radio frequency signal. At this point, the Mach-Zehnder modulator operates at its minimum bias point, and the center carrier is suppressed. The modulated optical signal output from the Mach-Zehnder modulator passes through the single-mode fiber to obtain a delayed optical signal. This delayed optical signal can be transmitted to a looper within the tunable fiber Bragg grating. The delayed optical signal originates from the input end of the tunable fiber Bragg grating (…). Figure 2 1 port in the middle) into the reflector end ( Figure 2 The chaotic photoelectric oscillator radio frequency signal, after being reflected by an adjustable fiber optic Lagrange grating, is output from port 2 (in the middle). Figure 2 (2 ports) input / output terminals ( Figure 2The chaotic photoelectric oscillator (OEO) radio frequency signal enters the OEO (a ring cavity composed of a frequency prediction device and a signal detection device) again. When there is a difference between the first-order sideband of the reflected chaotic OEO radio frequency signal and the first-order sideband directly modulated onto the laser output light (i.e., the optical carrier signal), the photodetector generates a radio frequency signal with a frequency equal to the difference between the two through the beat frequency effect. The radio frequency signal is then amplified by a frequency-tunable radio frequency amplifier and fed back into the radio frequency beam splitter, radio frequency analyzer, and low-noise amplifier to complete the entire loop. When the knob on the tunable fiber Bragg grating is adjusted, the length of the grating changes, and the wavelength of the reflected light also changes accordingly. Single-mode fiber increases the delay of the entire loop, thereby improving the quality factor of the output radio frequency signal. In this way, it is possible to detect unknown weak radar signals with high sensitivity over a wide frequency range, with a larger detection bandwidth and higher detection sensitivity than traditional electronic methods, capable of detecting weak signals as low as -70dBm.

[0083] As can be seen from the above technical solution, this application provides a signal detection system, the system comprising: a frequency prediction device and a signal detection device; the output terminal of the frequency prediction device is connected to the input terminal of the signal detection device; the frequency prediction device is used to generate a plurality of optical carrier signals; determine a plurality of radio frequency signals based on the plurality of optical carrier signals; obtain an estimated frequency of an incident signal based on the plurality of radio frequency signals; output the estimated frequency of the incident signal through the output terminal; the signal detection device is used to acquire the estimated frequency of the incident signal through the input terminal, and to generate optical carrier signals; generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the optical carrier signals; and detect a target signal using the chaotic photoelectric oscillator radio frequency signal. This embodiment can generate a chaotic photoelectric oscillator radio frequency signal by estimating the frequency of the incident signal and the optical carrier signal based on the environment. Then, the target signal (i.e., the weak microwave photon signal) can be detected using the chaotic photoelectric oscillator radio frequency signal. It can be seen that this embodiment can expand the bandwidth of the target signal (i.e., the weak signal) and reduce noise interference during signal processing. In other words, it can achieve the reception of the target signal (i.e., the weak signal) within a larger dynamic bandwidth range, thus improving the shortcomings of traditional signal detection methods, such as narrow working bandwidth and low detection sensitivity.

[0084] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The device and system embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0085] The above description is merely a preferred embodiment, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A signal detection system, characterized in that, The system includes: a frequency prediction device and a signal detection device; the output terminal of the frequency prediction device is connected to the input terminal of the signal detection device. The frequency estimation device is used to generate several optical carrier signals; to estimate the frequency of the incident signal based on several radio frequency signals; and to output the estimated frequency of the incident signal through the output terminal. The signal detection device is used to acquire the frequency of the estimated incident signal through the input terminal, and to generate an optical carrier signal; to generate a chaotic photoelectric oscillator radio frequency signal based on the frequency of the estimated incident signal and the optical carrier signal; and to detect the target signal using the chaotic photoelectric oscillator radio frequency signal. The frequency estimation device includes a laser, a radio frequency (RF) signal generation unit, and a digital-to-analog converter (DAC). The signal output terminal of the laser is connected to the input terminal of the RF signal generation unit, the output terminal of the RF signal generation unit is connected to the input terminal of the DAC, and the output terminal of the DAC is connected to the input terminal of the signal detection device. The laser is used to generate several optical carrier signals. The RF signal generation unit is used to determine several RF signals based on the several optical carrier signals. The DAC is used to estimate the frequency of the incident signal based on the several RF signals. The laser comprises two lasers, each of which generates an optical carrier signal; The radio frequency signal generation unit includes a wavelength division multiplexer (WDM), a polarization controller, a Mach-Zehnder modulator, a filter, a demultiplexer, and a photodetector. The input of the WDM is connected to the signal output of the laser; the output of the WDM is connected to the input of the polarization controller; the output of the polarization controller is connected to the input of the Mach-Zehnder modulator; the output of the Mach-Zehnder modulator is connected to the input of the filter; the output of the filter is connected to the input of the demultiplexer; the output of the demultiplexer is connected to the input of the photodetector; and the output of the photodetector is connected to the signal detection... The device's input terminal is connected to the following: the wavelength division multiplexer (WDM) is used to mix two optical carrier signals to obtain one optical carrier signal; the polarization controller is used to adjust the polarization state of the optical carrier signal to obtain a polarization-adjusted optical carrier signal; the Mach-Zehnder modulator is used to modulate the polarization-adjusted optical carrier signal to obtain a modulated optical signal; the filter is used to filter the modulated optical signal to obtain a carrier-suppressed optical signal; the deWDM multiplexer is used to deWDM the carrier-suppressed optical signal to obtain two optical signals; and the photodetector is used to perform beat frequency processing on the two optical signals to obtain two radio frequency signals. The signal detection device includes a laser, a signal generation unit, and a signal detection unit; the output terminal of the laser is connected to the input terminal of the signal generation unit, and the input terminal of the signal generation unit is connected to the output terminal of the frequency prediction device; the output terminal of the signal generation unit is connected to the input terminal of the signal detection unit; the output terminal of the signal detection unit is connected to the input terminal of the signal generation unit. The laser is used to generate an optical carrier signal; the signal generation unit is used to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the optical carrier signal; the signal detection unit is used to detect the target signal using the chaotic photoelectric oscillator radio frequency signal. The signal generation unit includes a polarization controller, a Mach-Zehnder modulator, a single-mode fiber, and a tunable fiber Bragg grating. The input of the polarization controller is connected to the signal output of the laser, the output of the polarization controller is connected to the input of the Mach-Zehnder modulator, the output of the Mach-Zehnder modulator is connected to the input of the single-mode fiber, and the output of the single-mode fiber is connected to the input of the tunable fiber Bragg grating. The polarization controller is used to adjust the polarization state of the optical carrier signal to obtain a polarization-adjusted optical carrier signal. The Mach-Zehnder modulator is used to modulate the polarization-adjusted optical carrier signal to obtain a modulated optical signal. The single-mode fiber is used to delay the modulated optical signal to obtain a delayed optical signal. The tunable fiber Bragg grating is used to generate a chaotic photoelectric oscillator radio frequency signal based on the estimated frequency of the incident signal and the delayed optical signal.

2. The system according to claim 1, characterized in that, The photodetector includes two photodetectors, each of which is used to receive a beam of light signal, perform beat frequency processing on the beam of light signal, and obtain the radio frequency signal corresponding to the beam of light signal.

3. The system according to claim 1, characterized in that, The signal detection unit includes: a coupler, a spectrum analyzer, a photodetector, a frequency-adjustable radio frequency amplifier, a radio frequency beam splitter, a radio frequency analyzer, and a low-noise amplifier; The input terminal of the coupler is connected to the output terminal of the tunable fiber Bragg grating, the output terminal of the coupler is connected to the input terminal of the spectrometer, the output terminal of the coupler is connected to the input terminal of the photodetector, the output terminal of the photodetector is connected to the input terminal of the frequency-tunable radio frequency amplifier, the output terminal of the frequency-tunable radio frequency amplifier is connected to the input terminal of the radio frequency beam splitter, the output terminal of the radio frequency beam splitter is connected to the input terminal of the radio frequency analyzer, the output terminal of the radio frequency beam splitter is connected to the input terminal of the low-noise amplifier, and the output terminal of the low-noise amplifier is connected to the input terminal of the Mach-Zehnder modulator. The coupler is used to split the chaotic photoelectric oscillator radio frequency signal into two chaotic photoelectric oscillator radio frequency signals. The spectrum analyzer is used to analyze the signal state of the radio frequency signal of the chaotic photoelectric oscillator; The photodetector is used to perform beat frequency processing on the radio frequency signal of the chaotic photoelectric oscillator to obtain a radio frequency signal; The frequency-adjustable radio frequency amplifier is used to amplify the radio frequency signal to obtain an amplified radio frequency signal; The radio frequency beam splitter is used to split the amplified radio frequency signal into two beams of the amplified radio frequency signal; The radio frequency analyzer is used to observe the amplified radio frequency signal in order to obtain the target signal; The low-noise amplifier is used to amplify the target signal in the amplified radio frequency signal.

4. The system according to claim 1, characterized in that, The tunable fiber Bragg grating also includes a reflector. The delayed optical signal is input to the input end of the tunable fiber Bragg grating. The delayed optical signal enters from the reflector. After the delayed optical signal is reflected by the fiber Bragg grating according to the estimated frequency of the incident signal, a chaotic photoelectric oscillator radio frequency signal is obtained. The chaotic photoelectric oscillator radio frequency signal enters the output end from the reflector.

5. The system according to claim 4, characterized in that, The tunable fiber Bragg grating is equipped with a knob. When the knob is adjusted, the length of the grating changes, and the wavelength of the reflected light also changes accordingly.

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