A Nyquist folding receiver method and system based on broadband optical comb

Abstract

This invention discloses a Nyquist folding reception method and system based on a broadband optical comb. The method includes generating equally spaced optical local oscillators with doubled bandwidth in the optical domain using a continuous wave light source and cascaded intensity modulators and dual-phase modulators. The cascaded modulators are simultaneously driven by a baseband SFM signal, and the modulation index and DC bias are jointly adjusted to achieve effective broadening and balanced distribution of the high-order spectrum. After the target RF signal and the optical local oscillator are mixed in the optical domain, the high-frequency RF signal is folded into the low sampling rate observation band by photoelectric detection and low-pass filtering. The time-frequency characteristics of the folded signal are used to determine the Nyquist zone index and reconstruct the signal. This invention does not require high-speed position modulation optical pulses, has a compact system structure, and is simple to implement. It achieves real-time reception of ultra-wideband RF signals under low-speed sampling conditions and is suitable for applications such as broadband radar, wireless communication, and cognitive wireless.

Description

Technical Field

[0001] This invention relates to the field of microwave signal measurement technology, and specifically to a Nyquist folding receiving method and system based on a broadband optical comb. Background Technology

[0002] In recent years, real-time reception of high-frequency broadband signals has had significant application value in wireless communication, radar detection, and cognitive radio. Traditional Nyquist sampling methods are limited by the cost, power consumption, and data throughput of high-speed analog-to-digital converters (ADCs), making it difficult to effectively acquire broadband signals. To overcome the Nyquist sampling bottleneck, various undersampling methods have been proposed in recent years, including coprime sampling, compressed sensing sampling, and Nyquist folded receivers (NYFR). The basic principle of NYFR is to mix the target signal with a position-modulated pulse train (PMPT) local oscillator, folding the signal spectrum of different Nyquist intervals (NZ) into the same Nyquist bandwidth, while simultaneously preserving the region number information through the pulse mixing process. The monitorable bandwidth of NYFR is inversely proportional to the pulse width of the pulse used; therefore, a high-quality PMPT is crucial for achieving broadband folding. However, electronic NYFRs are limited by electronic bandwidth when implementing the PMPT local oscillator, and cannot effectively support the acquisition of broadband signals in higher frequency bands.

[0003] Therefore, in recent years, photonic technology has been gradually introduced to construct photonic NYFR schemes, leveraging the advantages of ultra-wide bandwidth, low loss, and electromagnetic interference resistance in the optical domain to overcome electronic bottlenecks. The earliest photonic NYFR schemes migrated the pulse mixing process to the optical domain, but their PMPT still relied on zero-crossing detection of electrons, thus the detection bandwidth remained limited by the electronic bottleneck. To further overcome the limitations of electronic PMPT, one approach attempts to directly synthesize the target PMPT using a high-speed optical pulse source, proposing a scheme using high-speed digital sequence selected mode-locked laser (MLL) pulses. However, due to the resolution limitation of digital sequence selection, its detection bandwidth can only cover half of the MLL repetition frequency. Simultaneously, another approach proposes using broadband RF modulation with MLL combined with dispersive transmission to generate PMPT, achieving real-time Fourier transform based on the time-domain Talbot effect. This scheme requires high-precision dispersion control, and the power attenuation caused by optical path loss reduces the stability of the optical local oscillator. Another approach attempts to use an optical frequency comb as the local oscillator to avoid the need for explicit position modulation pulses, achieving unique signal identification through a frequency comb structure. However, such solutions often rely on multi-stage optoelectronic conversion links and complex frequency offset control loops, resulting in a complex system structure that is not conducive to multi-target broadband signal reception and practical engineering deployment. Summary of the Invention

[0004] The purpose of this invention is to provide a Nyquist folding reception method and system based on a broadband optical comb to solve the problems mentioned in the background art.

[0005] The present invention provides the following technical solution: a Nyquist folding reception method based on a broadband optical comb, comprising the following operational steps: Step S1: Output a continuous light signal through a continuous light source, and generate a narrow-band baseband SFM signal through a baseband signal generator.

[0006] Preferably, the optical signal passes through a frequency doubling modulation link formed by cascading a first intensity modulator and a dual-phase modulator to generate an optical frequency band with equal intervals and doubled bandwidth.

[0007] Preferably, the baseband SFM signal drives the first intensity modulator, the first phase modulator, and the second phase modulator to form an optical local oscillator signal with doubled bandwidth.

[0008] Preferably, the baseband SFM signal is loaded onto the RF port of the first intensity modulator, and the DC bias is set between the maximum bias point and the quadrature bias point, outputting an optical signal. The optical signal output from the first intensity modulator is then further input into the first phase modulator and the second phase modulator to output an optical signal. The first and second phase modulators introduce exponential phase modulation terms. By adjusting the phase modulation index, the modulation energy is effectively distributed to higher-order spectral components, expanding the effective bandwidth of the optical local oscillator. The first intensity modulator, the first phase modulator, and the second phase modulator are driven by the same baseband SFM signal, and the optical local oscillator spectral amplitude equalization is achieved by jointly adjusting the intensity modulation index, the phase modulation index, and the DC bias.

[0009] Step S2: Use an RF signal generator to generate the target RF signal to be received, and then use a second intensity modulator to perform optical domain mixing with the optical local oscillator signal to form a mixed spectrum.

[0010] Preferably, the second intensity modulator is biased to operate at the quadrature point to achieve double-sideband intensity modulation mixing between the target RF signal and the bandwidth-multiplying optical local oscillator signal. After optical domain mixing, the spectrum of the optical local oscillator signal is copied and symmetrically shifted around the frequency of the target RF signal.

[0011] Step S3: The mixed spectrum is connected to a photodetector for photoelectric conversion, converting the optical signal into an electrical signal. Then, a low-pass filter is used to filter out the spectral components in the electrical signal that are higher than the preset cutoff frequency, thus obtaining the intermediate frequency observation signal.

[0012] Preferably, the optical signal is converted into an electrical signal, which contains folded spectrum time-frequency information, including the bandwidth of the folded electrical signal, the Nyquist zone index of the original radio frequency signal, and the spectral direction. The Nyquist zone index is linearly related to the chirp rate of the baseband SFM signal, and the spectral direction can be determined by observing the initial phase in the folded time-frequency diagram of the band SFM signal.

[0013] Step S4: The intermediate frequency observation signal is sampled at low speed using a low-speed sampling module. The intermediate frequency observation signal after low-speed sampling is then processed by a digital signal processing module to identify the Nyquist interval, calculate the frequency, and reconstruct the signal, thus restoring the original radio frequency signal.

[0014] Preferably, by analyzing the folded signal and its time-frequency distribution characteristics, the NZ to which the original radio frequency signal belongs is determined, thereby enabling the identification and reconstruction of single-tone signals, multi-tone signals, and broadband LFM signals.

[0015] On the other hand, the present invention also provides a Nyquist folding receiving system based on a broadband optical comb, which executes a Nyquist folding receiving method based on a broadband optical comb, including the following functional modules connected in sequence: LD light source: used to generate continuous wave optical carriers; Baseband signal generator: used to generate the narrowband SFM signal required for the optical local oscillator generation module; First intensity modulator: used to intensity modulate the continuous wave optical carrier generated by the LD light source, and load the narrowband SFM signal generated by the baseband signal generator onto the optical carrier to form a preliminary modulated optical signal; First phase modulator: used to perform phase modulation on the optical signal modulated by the first intensity modulator, introducing a specific phase shift to optimize the spectral characteristics of the optical signal; Second phase modulator: used to further modulate the phase of the optical signal to generate an optical local oscillator signal with a specific frequency interval and bandwidth; The first intensity modulator, the first phase modulator, and the second phase modulator are cascaded together to form an optical local oscillator generation module; Radio frequency signal source: used to generate the radio frequency signal to be tested; Second intensity modulator: used to realize optical domain mixing of optical local oscillator and radio frequency signal under test; Photodetector: Used to convert optical signals into electrical signals; Low-pass filters and analog-to-digital converters: used to achieve low-speed sampling and signal acquisition; Signal processing module: used to identify and reconstruct the original radio frequency signal using the time-frequency characteristics of the folded intermediate frequency signal; The cutoff frequency of the low-pass filter is equal to half the center frequency of the baseband SFM signal. It is used to filter out high-frequency components that are not folded into the observation bandwidth, and only retain the folded intermediate frequency signal.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) Achieving ultra-wideband low-speed reception: This invention generates an optical local oscillator spectrum with stable amplitude and doubled bandwidth in the optical domain, folding the high-frequency broadband radio frequency signal to a low-frequency observation bandwidth, thereby achieving effective reception of 0–29 GHz radio frequency signals under low sampling rate conditions and reducing dependence on high-speed analog-to-digital converters. (2) Avoiding the bottleneck of high-speed position modulation: The present invention uses a continuous wave light source combined with cascaded intensity modulation and phase modulation to generate an optical local oscillator, replacing the traditional method of realizing high-speed position modulation optical pulses in photonic Nyquist folded receivers, thus eliminating the limitations of electronic terminal bandwidth and stability. (3) Simplified system structure and high integration: The present invention completes optical local oscillator generation, radio frequency signal mixing and spectrum folding in a single optical link, without the need for optical frequency comb, multi-level frequency shift loop or complex phase control structure, thus reducing system complexity and implementation cost; (4) Applicable to multiple types of broadband signals: This invention realizes Nyquist zone index determination by utilizing the time-frequency characteristics of the folded signal. This invention can accurately identify and reconstruct single-tone, multi-tone and LFM signals, and has good versatility and practical value. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the system structure provided in the embodiment of the present invention; Figure 2 This is a schematic diagram of the simulation results of the optical local oscillator provided in the embodiment of the present invention; Figure 3 This is a schematic diagram of the simulation results of the time-frequency diagram of single-tone signal reception provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the simulation results of the time-frequency diagram of multi-tone signal reception provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the simulation results of the LFM signal reception time-frequency diagram provided in the embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 Combination Figure 1 As shown, the present invention provides the following technical solution: a Nyquist folding receiver system based on a broadband optical comb, comprising an LD light source, a baseband signal generator, a first intensity modulator MZM1, a first phase modulator PM1, a second phase modulator PM2, an RF signal source, a second intensity modulator MZM2, a photodetector, a low-pass filter, and an analog-to-digital converter connected in sequence. In this embodiment, the functions of each module are as follows: LD light source: used to generate continuous wave optical carriers; Baseband signal generator: responsible for generating the narrowband SFM signal required for the optical local oscillator generation module; First intensity modulator MZM1: Used to intensity modulate the continuous wave optical carrier generated by the LD light source, and load the narrowband SFM signal generated by the baseband signal generator onto the optical carrier to form a pre-modulated optical signal; The first phase modulator PM1 is used to perform phase modulation on the optical signal modulated by MZM1. By introducing a specific phase shift, the spectral characteristics of the optical signal are optimized, preparing for the subsequent frequency comb generation. The second phase modulator PM2 is used to further modulate the phase of the optical signal. It works with PM1 to achieve more complex phase modulation effects and ultimately generates an optical local oscillator signal with specific frequency intervals and bandwidth, providing a high-quality optical local oscillator for subsequent optical domain mixing. The first intensity modulator MZM1, the first phase modulator PM1, and the second phase modulator PM2 are cascaded to form an optical local oscillator generation module. Radio frequency signal source: used to generate the radio frequency signal to be tested; Second intensity modulator MZM2: used to realize optical domain mixing of the optical local oscillator and the radio frequency signal under test; Photodetector: Used to convert optical signals into electrical signals; Low-pass filters and analog-to-digital converters: used to achieve low-speed sampling and signal acquisition; Signal processing module: used to identify and reconstruct the original radio frequency signal by utilizing the time-frequency characteristics of the folded intermediate frequency signal.

[0020] Example 2 Combination Figures 2-5 As shown, the present invention provides the following technical solution: a Nyquist folding reception method based on a broadband optical comb, taking a baseband SFM signal with a center frequency of 2GHz and a bandwidth of 40MHz as an example, including the following operating steps: Step S1: Generation of optical local oscillator signal.

[0021] In this embodiment, the present invention outputs a continuous wave optical carrier signal through an LD light source. ,in For the amplitude of the light field, Given its frequency, a baseband SFM signal is then generated using a baseband signal generator. : ,in, Signal amplitude, center frequency Modulation frequency Modulation index =2. The baseband SFM signal... The signal is applied to the RF port of the first intensity modulator MZM1, with the DC bias set between the maximum bias point and the quadrature bias point, and the output optical signal is generated. as follows: in, and These represent the DC bias and half-wave voltage of the intensity modulator MZM1, respectively, and the modulation depth. bias phase shift , For zero-order Bessel functions, the amplitude of the optical carrier component is given. , , These represent first- to third-order Bessel functions, corresponding to the amplitudes of the first- to third-order sideband components generated after modulation. Due to the nonlinear response characteristics of the intensity modulator, under baseband SFM signal modulation conditions, equally spaced frequency doubling sidebands can be generated, with their instantaneous frequency and modulation slope changing linearly with the sideband order. However, limited by the amplitude saturation effect of the intensity modulator, simply increasing the modulation depth will only redistribute optical power within a finite number of orders, and higher-order sidebands will still be suppressed. When the first intensity modulator is biased between the maximum bias point and the quadrature bias point, the output spectrum mainly consists of the optical carrier and the first-order sidebands.

[0022] To enhance higher-order frequency components, the output signal of the first intensity modulator is further input to the first phase modulator PM1 and the second phase modulator PM2, and its optical signal... The output is: in, and These represent the half-wave voltage and modulation depth of the phase modulator, respectively. For the nth-order Bessel function, the half-wave voltages of the first phase modulator PM1 and the second phase modulator PM2 are set to be the same. Driven by the same baseband SFM signal, the dual-phase modulator introduces a larger exponential phase modulation term. Compared to intensity modulation, it is not limited by amplitude saturation and can effectively achieve spectral expansion and enhancement of higher-order frequency components. By jointly adjusting the DC bias of the first intensity modulator and the modulation depth of the dual-phase modulator, a balanced amplitude distribution of higher-order sidebands can be achieved, synthesizing an optical local oscillator signal with equal amplitude, equal spacing, and doubled bandwidth.

[0023] Step S2: Optical domain mixing of the target radio frequency signal.

[0024] In this embodiment, the radio frequency signal generator in this invention generates the target radio frequency signal to be received as follows: , The frequency of the signal to be measured. It carries phase information. This signal is input to the RF port of the second intensity modulator MZM2. The second intensity modulator is biased to operate at the quadrature point, realizing double-sideband intensity modulation mixing between the target RF signal and the bandwidth-multiplying optical local oscillator.

[0025] For example, after optical domain mixing, the spectrum of the optical local oscillator is copied and symmetrically shifted around the target radio frequency signal frequency to achieve spectrum shift of the target signal. Through this process, the radio frequency signal located in the higher-order Nyquist zone is mapped into the low-frequency observation bandwidth, while its Nyquist zone index information is embedded in the folded signal in the form of modulation.

[0026] Step S3: Photoelectric conversion and low-speed sampling.

[0027] In this embodiment, the output optical signal of the second intensity modulator MZM2 undergoes photoelectric conversion via a photodetector to obtain an electrical signal containing folded spectrum information. This electrical signal is then input to a low-pass filter to filter out spectral components above a preset cutoff frequency, retaining only the effective signal within the observation bandwidth. The output result is as follows: in, Indicates the modulation scaling factor. Indicates the center frequency of the folded signal within the observation band. Indicates the spectral direction of the folded signal within the observed frequency band. This indicates the NZ number related to the folding interval of the original signal carried by the folded signal within the observation band. As shown in the above formula, the bandwidth of the folded signal is linearly related to both the Nyquist zone index M and the chirp rate of the baseband SFM signal. Furthermore, the spectral direction is determined by the initial phase in the folding time-frequency diagram of the observed SFM signal. It is -1 or +1. The filtered electrical signal is sampled at a low speed by an analog-to-digital converter. The sampling rate is significantly lower than the highest frequency of the target RF signal, thus achieving sub-Nyquist sampling.

[0028] Step S4: Signal processing and frequency reconstruction.

[0029] In this embodiment, the sampled digital signal is input into the signal processing module, and characteristic parameters such as the center frequency, bandwidth, and spectral direction of the folded signal are extracted through time-frequency analysis. Based on the correspondence between the signal folding bandwidth and the Nyquist zone index M, combined with the spectral direction... Criterion and center frequency of folded signal It can uniquely determine the NZ number and its true frequency of the original radio frequency signal. This enables accurate identification and reconstruction of the original radio frequency signal.

[0030] In this embodiment, as Figure 2 The schematic diagram of the spectral simulation results of the bandwidth-multiplying optical local oscillator shows that equal-interval, amplitude-balanced multi-order frequency components can be obtained through a cascaded structure of intensity modulation and dual-phase modulation. For example... Figure 3 The diagram shows the simulation results of the received time-frequency diagrams for single-tone radio frequency signals located in different Nyquist zones. The signals under test are 2.5 GHz and 28.5 GHz single-tone signals. Taking the 2.5 GHz signal on the left as an example, the time-frequency characteristics of its folded signal are as follows: center frequency... =0.5GHz, bandwidth 40MHz corresponding modulation scaling factor The spectral direction corresponding to an initial phase of 0 Therefore, M is +1, thus obtaining the reconstruction frequency. Similarly, the bandwidth of the folded time-frequency diagram of the 28.5 GHz single-tone signal on the right increases to 560 MHz, while other parameters remain the same, with M at +14, consistent with the expected image parameters. The RF signals from different Nyquist zones exhibit different bandwidth and frequency modulation direction characteristics after folding, verifying the invention's ability to distinguish signals from multiple Nyquist zones and its 29 GHz reception range.

[0031] In this embodiment, as Figure 4 The diagram shows the simulation results of the time-frequency diagram during multi-tone radio frequency (SFM) signal reception. The input signals are 3.2 GHz and 6.2 GHz dual-tone signals, corresponding to center frequencies of 0.8 GHz and 0.2 GHz, bandwidths of 80 MHz and 120 MHz respectively within a single cycle, and initial phases of [missing information]. The spectral directions of -1 and +1 are respectively, therefore M is -2 and +3, resulting in reconstructed frequencies of 3.2 GHz and 6.2 GHz, which is completely consistent with expectations. Multiple cross-Nyquist zone signals form multiple distinguishable time-frequency trajectories within the observation bandwidth, proving that this invention has the capability for simultaneous reception and identification of multiple signals. For example... Figure 5 The diagram shows the simulation results of the time-frequency diagram of the received SFM signal. The center frequency of the LFM signal under test is 4.5 GHz, the bandwidth is 200 MHz, the period is 1 μs, and the corresponding chirp rate is -200 MHz / μs. Figure 5 The center frequency of the folded signal can be extracted as 0.5 GHz, the slope of the folded signal is -200 MHz / µs, and the bandwidth of the SFM signal in a single cycle is 80 MHz with an initial phase of 0. Therefore, N is +2, and the center frequency of the recovered signal is 4.5 GHz, corresponding to a chirp rate of -200 MHz / µs. Simulation results show that the bandwidth and frequency modulation slope of the folded signal are consistent with the theoretical analysis, and accurate reconstruction of the broadband LFM signal can be achieved.

[0032] This invention achieves optical domain frequency shifting and folded sampling of high-frequency broadband radio frequency signals through a bandwidth-doubling optical local oscillator. It enables real-time reception and reconstruction of single-tone, multi-tone, and broadband LFM signals within the 0-29 GHz range using only a low-speed analog-to-digital converter with a sampling rate of 2 GS / s. Compared to existing photonic Nyquist folded receiver schemes, this invention features a simpler system structure, higher stability, stronger scalability, and eliminates the need for a high-speed PMPT or multi-channel parallel structure, demonstrating promising engineering implementation prospects.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Nyquist folding receiver method based on a broadband optical comb, characterized in that: The following steps are included: Step S1: Output a continuous light signal through a continuous light source, and generate a narrow-band baseband SFM signal through a baseband signal generator; The continuous optical signal is passed through a frequency doubling modulation link formed by cascading a first intensity modulator and a dual-phase modulator to generate an optical frequency band with equal intervals and doubled bandwidth. The baseband SFM signal drives the first intensity modulator, the first phase modulator, and the second phase modulator respectively to form an optical local oscillator signal with doubled bandwidth; Step S2: Use an RF signal generator to generate the target RF signal to be received, and then use a second intensity modulator to perform optical domain mixing with the optical local oscillator signal to form a mixed spectrum; Step S3: The mixed spectrum is connected to the photodetector for photoelectric conversion, converting the optical signal into an electrical signal. Then, a low-pass filter is used to filter out the spectral components in the electrical signal that are higher than the preset cutoff frequency to obtain the intermediate frequency observation signal. Step S4: The intermediate frequency observation signal is sampled at low speed using a low-speed sampling module. The signal processing module is then used to identify the Nyquist interval, calculate the frequency, and reconstruct the signal from the low-speed sampled intermediate frequency observation signal, thus restoring the original radio frequency signal.

2. The Nyquist folding reception method based on a broadband optical comb according to claim 1, characterized in that: Step S1 includes: The baseband SFM signal is applied to the RF port of the first intensity modulator, and the DC bias is set between the maximum bias point and the quadrature bias point, outputting an optical signal. ; The optical signal output from the first intensity modulator is then further input into the first phase modulator and the second phase modulator to output an optical signal. .

3. The Nyquist folding reception method based on a broadband optical comb according to claim 2, characterized in that: The first and second phase modulators introduce exponential phase modulation terms. By adjusting the phase modulation index, the modulation energy is effectively distributed to higher-order spectral components, thus extending the effective bandwidth of the optical local oscillator.

4. The Nyquist folding reception method based on a broadband optical comb according to claim 3, characterized in that: The first intensity modulator, the first phase modulator, and the second phase modulator are driven by the same baseband SFM signal, and optical local oscillator spectrum amplitude equalization is achieved by jointly adjusting the intensity modulation index, the phase modulation index, and the DC bias.

5. The Nyquist folding reception method based on a broadband optical comb according to claim 4, characterized in that: Step S2 includes: the second intensity modulator is biased to the orthogonal point working state to realize double-sideband intensity modulation mixing between the target radio frequency signal and the bandwidth-multiplying optical local oscillator signal. After optical domain mixing, the spectrum of the optical local oscillator signal is copied and symmetrically shifted around the frequency of the target radio frequency signal.

6. The Nyquist folding reception method based on a broadband optical comb according to claim 5, characterized in that: In step S3, the optical signal is converted into an electrical signal. The electrical signal contains folded spectrum time-frequency information, including the bandwidth of the folded electrical signal, the Nyquist zone index of the original radio frequency signal, and the spectral direction. The Nyquist zone index is linearly related to the chirp rate of the baseband SFM signal, and the spectral direction can be determined by observing the initial phase in the folded time-frequency diagram of the band SFM signal.

7. The Nyquist folding reception method based on a broadband optical comb according to claim 6, characterized in that: Step S4 includes: analyzing the folded signal and time-frequency distribution characteristics, determining the Nyquist zone index of the original radio frequency signal, and realizing the identification and reconstruction of single-tone signals, multi-tone signals and broadband LFM signals.

8. A Nyquist folding receiver system based on a broadband optical comb, characterized in that: The method for receiving Nyquist-based folded receivers based on broadband optical combs as described in any one of claims 1-7 includes sequentially connecting the following functional modules: LD light source: used to generate continuous wave optical carriers; Baseband signal generator: used to generate the narrowband SFM signal required for the optical local oscillator generation module; First intensity modulator: used to intensity modulate the continuous wave optical carrier generated by the LD light source, and load the narrowband SFM signal generated by the baseband signal generator onto the optical carrier to form a preliminary modulated optical signal; First phase modulator: used to perform phase modulation on the optical signal modulated by the first intensity modulator, introducing a specific phase shift to optimize the spectral characteristics of the optical signal; Second phase modulator: used to further modulate the phase of the optical signal to generate an optical local oscillator signal with a specific frequency interval and bandwidth; Radio frequency signal source: used to generate the radio frequency signal to be tested; Second intensity modulator: used to realize optical domain mixing of optical local oscillator and radio frequency signal under test; Photodetector: Used to convert optical signals into electrical signals; Low-pass filters and analog-to-digital converters: used to achieve low-speed sampling and signal acquisition; Signal processing module: used to identify and reconstruct the original radio frequency signal by utilizing the time-frequency characteristics of the folded intermediate frequency signal.

9. A Nyquist folding receiver system based on a broadband optical comb according to claim 8, characterized in that: The first intensity modulator, the first phase modulator, and the second phase modulator are cascaded to form an optical local oscillator generation module.

10. A Nyquist folding receiver system based on a broadband optical comb according to claim 9, characterized in that: The cutoff frequency of the low-pass filter is equal to half the center frequency of the baseband SFM signal. It is used to filter out high-frequency components that are not folded into the observation bandwidth, and only retain the folded intermediate frequency signal.

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