A signal analysis system and method
By using laser-locked module spectral splitting and optical phase-locked loop technology, the problem of insufficient accuracy in the analysis of extremely weak radio frequency microwave signals in existing methods has been solved, achieving highly accurate signal detection and extraction and improving signal analysis capabilities.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING PEGO MEASUREMENT&CONTROL TECH CO LTD
- Filing Date
- 2026-06-09
- Publication Date
- 2026-07-10
AI Technical Summary
Existing electrical detection, electrical mixing downconversion, and microwave photon detection methods are unable to accurately detect and extract extremely weak radio frequency microwave signals, resulting in limited signal analysis capabilities.
The initial optical signal is split into a first optical signal and a second optical signal using a laser locking module. The first optical signal is then modulated with the radio frequency signal under test to generate a driving signal. At the same time, an optical phase-locked loop is formed in the signal generation module. By synchronizing the absolute phase of the optical carrier and the local oscillator of the optical frequency comb, the frequency error caused by temperature drift is eliminated, thereby improving the accuracy of detection and extraction.
It achieves highly accurate detection and extraction of radio frequency microwave signals, improves signal analysis capabilities, and eliminates frequency errors caused by temperature drift.
Smart Images
Figure CN122372097A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of signal processing technology, and more specifically to a signal analysis system and method. Background Technology
[0002] Currently, the methods for detecting and analyzing radio frequency (RF) microwave signals are mainly divided into three categories: electrical detection, electrical mixing downconversion, and microwave photon detection. However, these methods cannot accurately detect and extract RF microwave signals when faced with extremely weak signals, such as signals at the -100dBm level, resulting in limited signal analysis capabilities for RF microwave signals. Summary of the Invention
[0003] This invention provides a signal analysis system and method to solve the problems of low accuracy and limited signal analysis capabilities in the detection and extraction of radio frequency microwave signals.
[0004] In a first aspect, the present invention provides a signal analysis system, which includes: a laser locking module, a signal generation module, a signal conversion module, and a signal processing module; The laser locking module is connected to the signal generation module and the signal conversion module. The laser locking module is used to split the initial optical signal into a first optical signal and a second optical signal. The first optical signal is output to the signal conversion module and modulated with the radio frequency signal to be tested input to the signal conversion module. The second optical signal is used to lock the initial optical signal and is simultaneously output to the signal generation module. The signal generation module includes a first optical comb generator, a first photodetector, a mixer, and an oscillator. The first optical comb generator, the first photodetector, the mixer, and the oscillator form a closed-loop connection. The laser locking module is connected to the first optical comb generator and inputs the second optical signal into the first optical comb generator. The reference signal corresponding to the second optical signal is input into the mixer. The oscillator is connected to the signal conversion module and the signal processing module respectively and outputs driving signals to the signal conversion module and the signal processing module respectively. The signal conversion module is connected to the signal processing module.
[0005] In one optional implementation, the laser locking module includes: a beam splitting unit, a locking unit, and a light extraction unit; The beam splitting unit is connected to the locking unit and the signal conversion module. The beam splitting unit splits the initial optical signal into a first optical signal and a third optical signal. The first optical signal is output to the signal conversion module and the third optical signal is output to the locking unit. The locking unit includes a resonator, and a third optical signal is input to the resonator; The optical extraction unit is connected in the feedback loop of the resonator and the beam splitter, and is connected to the first optical comb generator. The optical extraction unit consists of multiple spaced-connected optical couplers and optical isolators. The optical signal fed back in the feedback loop is extracted and isolated through the multiple spaced-connected optical couplers and optical isolators to obtain the second optical signal.
[0006] In one optional implementation, the beam splitting unit includes: multiple beam splitting links and an optical combiner, wherein the multiple beam splitting links include at least a first beam splitting link and a second beam splitting link; The first optical splitting link includes a first laser and a first optical coupler. The first laser is connected to the first optical coupler, and the first output end of the first optical coupler is connected to the first input end of the optical combiner. The second beam splitting link includes a second laser and a second optical coupler. The second laser is connected to the second optical coupler. The first output end of the second optical coupler is connected to the second input end of the optical combiner. The first optical coupler and the second optical coupler have the same beam splitting ratio. The output of the optical combiner is connected to the locking unit.
[0007] In one optional implementation, the locking unit further includes a second photodetector and a control unit; The second photodetector is connected to the optical coupler that outputs the second optical signal in the light extraction unit, and the second photodetector is used to detect the output power of the light extraction unit. The control unit is connected to the resonator and the second photodetector respectively. The control unit is used to adjust the operating parameters of the resonator based on the output power detected by the second photodetector.
[0008] In one alternative implementation, the control unit is also connected to the first laser and the second laser in the beam splitting unit, and the control unit is also used to adjust the operating parameters of the first laser and the second laser in the beam splitting unit based on the output power detected by the second photodetector.
[0009] In one optional implementation, the signal conversion module includes at least one signal conversion link, which includes a modulator, a second optical comb generator, and a third photodetector, wherein the modulator, the second optical comb generator, and the third photodetector are connected in sequence. The first optical signal and the radio frequency signal under test are input to the modulator, and the driving signal is input to the second optical comb generator to drive the second optical comb generator to work.
[0010] In one optional implementation, if the signal conversion module includes a signal conversion link, the first output terminal of the first optical coupler or the first output terminal of the second optical coupler in the laser locking module is connected to the modulator to output a first optical signal to the modulator.
[0011] In one optional implementation, if the signal conversion module includes multiple signal conversion links, the signal conversion links included in the signal conversion module correspond one-to-one with the beam splitting links included in the laser locking module; In the laser locking module, the first output terminal of the optical coupler in the beam splitting link is connected to the modulator in the corresponding signal conversion link, and outputs the first optical signal to the modulator in the corresponding signal conversion link.
[0012] In one optional implementation, the signal processing module includes at least one analog-to-digital converter, a clock control unit, and a digital signal processing unit; In this embodiment, at least one analog-to-digital converter is connected to a digital signal processing unit and the digital signal processing unit respectively; The clock control unit is connected to the signal generation module and is used to convert the drive signal generated by the signal generation module into a clock signal.
[0013] In one alternative implementation, the system further includes a radio frequency conditioning module, and the signal processing module further includes a digital-to-analog converter; The digital-to-analog converter is connected to the digital signal processing unit and the radio frequency conditioning module. The digital-to-analog converter is used to convert the reference signal of the radio frequency signal under test output by the digital signal processing unit into an analog reference signal and output it to the radio frequency conditioning module. The RF conditioning module is connected to the signal conversion module. The RF conditioning module is used to perform self-calibration of the RF signal under test based on the analog reference signal output by the digital-to-analog converter.
[0014] In one optional implementation, the analog-to-digital converter included in the signal processing module corresponds one-to-one with the signal conversion link included in the signal conversion module, and the analog-to-digital converter is connected to the third photodetector of the corresponding signal conversion link.
[0015] The signal analysis system provided in this embodiment of the invention uses a laser locking module to split the initial optical signal into a first optical signal and a second optical signal. The first optical signal is modulated with the radio frequency signal under test, and the second optical signal is used to generate a driving signal. Simultaneously, in the signal generation module, the first optical comb spectrum generator, the first photodetector, the mixer, and the oscillator are linked in a closed loop to form an optical phase-locked loop, generating a stable driving signal. The driving signal drives the signal conversion module and the signal processing module, thereby achieving absolute phase synchronization of the optical carrier and the optical frequency comb local oscillator within the signal analysis system, that is, achieving source synchronization of the signal analysis system. This eliminates frequency errors caused by temperature drift, improves the accuracy of detection and extraction of radio frequency microwave signals, and thus enhances the signal analysis capability of radio frequency microwave signals.
[0016] In a second aspect, the present invention provides a signal analysis method, applied to a signal analysis system of the first aspect or any corresponding embodiment thereof, the method comprising: In response to the input of the radio frequency signal under test, the first optical signal and the radio frequency signal under test are input to the signal conversion module, and the signal conversion module is driven by the driving signal output by the signal generation module to perform signal conversion on the radio frequency signal under test to obtain the beat frequency signal corresponding to the radio frequency signal under test. The first optical signal is obtained by splitting the initial optical signal based on the laser locking module, and the first optical signal is used to modulate the signal with the radio frequency signal under test. Based on the signal processing module, the beat frequency signal corresponding to the RF signal under test is processed and analyzed to obtain the analysis results of the RF signal under test.
[0017] In one optional implementation, a first optical signal and the radio frequency signal under test are input to a signal conversion module, and the signal conversion module is driven to perform signal conversion on the radio frequency signal under test based on the driving signal output by the signal generation module, to obtain a beat frequency signal corresponding to the radio frequency signal under test, including: The first optical signal and the radio frequency signal under test are modulated by the modulator of the input signal conversion module to obtain the optical signal corresponding to the radio frequency signal under test; The second optical comb spectrum generator, based on the driving signal conversion module, converts the optical signal corresponding to the radio frequency signal under test into the corresponding beat frequency signal. The third photodetector based on the signal conversion module converts the beat frequency signal corresponding to the radio frequency signal under test into an electrical signal.
[0018] In one optional implementation, based on the signal processing module, the beat frequency signal corresponding to the radio frequency signal under test is processed and analyzed to obtain the analysis result of the radio frequency signal under test, including: Based on the analog-to-digital converter in the signal processing module, the beat frequency signal corresponding to the radio frequency signal under test is converted into the corresponding digital signal. Based on the digital signal processing unit in the signal processing module, the digital signal corresponding to the radio frequency signal under test is processed to obtain the analysis results of the radio frequency signal under test.
[0019] The signal analysis method provided in this invention modulates the first optical signal output by the laser locking module and the radio frequency signal under test, generates a driving signal based on the second optical signal output by the laser locking module, and uses the driving signal to drive the signal conversion of the radio frequency signal under test and the signal processing of the beat frequency signal corresponding to the radio frequency signal under test. This achieves absolute phase synchronization of the optical carrier and the local oscillator of the optical frequency comb within the signal analysis system, i.e., source synchronization of the signal analysis system. This eliminates frequency errors caused by temperature drift, improves the accuracy of detection and extraction of radio frequency microwave signals, and thus enhances the signal analysis capability of radio frequency microwave signals. Attached Figure Description
[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of the structure of a signal analysis system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a laser locking module in a signal analysis system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the architecture of a laser locking module in a signal analysis system according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the signal conversion link in a signal analysis system according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the signal processing module in the signal analysis system according to an embodiment of the present invention; Figure 6 This is a schematic flowchart of a signal analysis method according to an embodiment of the present invention.
[0022] Explanation of reference numerals in the attached figures: 1-Laser locking module; 11-Splitting unit; 12-Locking unit; 13-Light extraction unit; 2-Signal generation module; 3-Signal conversion module; 4-Signal processing module. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.
[0024] It is understood that before using the technical solutions disclosed in the various embodiments of the present invention, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in the present invention and their authorization should be obtained in accordance with relevant laws and regulations through appropriate means.
[0025] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.
[0026] Currently, the methods for detecting and analyzing radio frequency (RF) microwave signals are mainly divided into three categories: electrical detection, electrical mixing downconversion, and microwave photon detection. However, these methods cannot accurately detect and extract RF microwave signals when faced with extremely weak signals, such as signals at the -100dBm level, resulting in limited signal analysis capabilities for RF microwave signals.
[0027] In electrical detection technology, Schottky diodes are commonly used as microwave power meters, utilizing their nonlinear conductivity to convert radio frequency power into DC voltage. However, diode detection is limited by its tangential signal sensitivity. Without chopping or cryogenic cooling, its detection limit is typically around -60dBm to -70dBm. For weak signals in the -100dBm range, the weak voltage output by the diode is completely drowned out by shot noise and thermal noise. Furthermore, diode detection is a broadband integral response, unable to distinguish specific frequency components of a signal. In complex electromagnetic environments, broadband noise floor and interference signals from other frequency bands are detected together, leading to significant measurement errors for weak target signals. In addition, the current-voltage characteristics of Schottky diodes are severely affected by temperature, requiring complex temperature compensation circuits. Moreover, its square law region is only effective under small signals, with a limited dynamic range, and linearity deteriorates under large signals.
[0028] In electrical mixing downconversion technology, an electrical mixer is typically used to mix the high-frequency radio frequency (RF) signal with the local oscillator (LO) signal, downconverting it to an intermediate frequency (IF), and then sampling it using a low-frequency analog-to-digital converter (ADC). However, passive electrical mixers typically have a 6-10 dB conversion loss, causing the already weak RF signal to attenuate before entering the IF amplification link, leading to a deterioration of the system noise and making it difficult to extract the RF signal from the noise floor. Furthermore, the LO-RF and LO-IF ports of electrical mixers have limited isolation, making it easy for strong LO signals to leak into the RF ports, creating self-interference or causing front-end amplifier saturation. Simultaneously, electrical mixing not only generates difference frequency signals but also a large number of MxN combined spurious frequencies, affecting spectral purity, limiting the spurious-free dynamic range, and making it difficult for electrical mixers to maintain a flat response in the ultra-wideband range of DC-60 GHz. This often requires segmented switching of multiple mixers, increasing system complexity and cost.
[0029] In microwave photonics detection technology, the high bandwidth of optical links is typically utilized for signal processing. However, in current self-injection locking or opto-oscillator architectures, the modulation optical path and the feedback locking optical path are often coupled together. When the main optical path undergoes significant RF modulation or power adjustment, the resulting reflected light or load changes can disturb the resonant cavity state of the laser, leading to locking instability. Furthermore, current microwave photonics algorithms lack high-precision opto-coordination mechanisms. The relative intensity noise and phase noise of the laser are directly transmitted to the intermediate frequency signal, resulting in high measurement noise floor, which cannot meet the requirements of precise phase noise analysis. Simultaneously, traditional single-channel opto-detection is limited by the shot noise limit of the detector. When detecting extremely weak signals, the photocurrent is minimal, and shot noise becomes the dominant noise source, limiting further improvement in the signal-to-noise ratio.
[0030] Based on this, the present invention provides a signal analysis system and method. A laser locking module splits the initial optical signal into a first optical signal and a second optical signal. The first optical signal is modulated with the radio frequency signal under test, and the second optical signal is used to generate a driving signal. Simultaneously, in the signal generation module, a first optical comb generator, a first photodetector, a mixer, and an oscillator are linked in a closed loop to form an optical phase-locked loop, generating a stable driving signal. This driving signal drives the signal conversion module and the signal processing module, thereby achieving absolute phase synchronization of the optical carrier and the optical comb local oscillator within the signal analysis system, i.e., source synchronization of the signal analysis system. This eliminates frequency errors caused by temperature drift, improves the accuracy of detecting and extracting radio frequency microwave signals, and ultimately enhances the signal analysis capability of radio frequency microwave signals.
[0031] On one hand, according to an embodiment of the present invention, a signal analysis system embodiment is provided. Figure 1 This is a schematic diagram of the structure of a signal analysis system according to an embodiment of the present invention, such as... Figure 1 As shown, the system includes: a laser locking module 1, a signal generation module 2, a signal conversion module 3, and a signal processing module 4. The laser locking module 1 is connected to the signal generation module 2 and the signal conversion module 3. The signal generation module 2 is connected to both the signal conversion module 3 and the signal processing module 4. The signal conversion module 3 is also connected to the signal processing module 4.
[0032] In this embodiment of the invention, the laser locking module 1 is used to split the initial optical signal into a first optical signal and a second optical signal. The first optical signal is output to the signal conversion module 3 and modulated with the radio frequency signal to be tested input to the signal conversion module 3. The second optical signal is used to lock the initial optical signal and is simultaneously output to the signal generation module 2 so that the signal generation module 2 generates a driving signal based on the second optical signal.
[0033] In embodiments of the present invention, such as Figure 1As shown, the signal generation module 2 includes a first optical comb generator, a first photodetector, a mixer, and an oscillator. The first optical comb generator, the first photodetector, the mixer, and the oscillator form a closed-loop connection, constituting an optical phase-locked loop. Simultaneously, the laser locking module 1 is connected to the first optical comb spectrum generator, inputting the second optical signal into the first optical comb spectrum generator. The reference signal corresponding to the second optical signal is input into the mixer. The second optical signal serves as the external reference optical signal input to the signal generation module 2. After being processed by the first optical comb spectrum generator and the first photodetector, the second optical signal reaches the mixer and is phase-discriminated with the local reference signal in the signal generation module 2, i.e., the reference signal corresponding to the second optical signal. This controls the oscillator to generate a highly stable radio frequency signal, which is the drive signal. The oscillator is connected to the signal conversion module 3 and the signal processing module 4, respectively, and outputs the drive signal to the signal conversion module 3 and the signal processing module 4, respectively. This achieves absolute phase synchronization of the optical carrier and the optical comb local oscillator within the signal analysis system, i.e., source synchronization of the signal analysis system. This eliminates frequency errors caused by temperature drift, improves the accuracy of detection and extraction of radio frequency microwave signals, and thus enhances the signal analysis capability of radio frequency microwave signals.
[0034] In one alternative implementation, the signal generation module 2 further includes an optical amplifier connected to the first optical comb generator for amplifying the input second optical signal.
[0035] In one optional implementation, the signal generation module 2 further includes an optical filter connected between the first optical comb generator and the first photodetector, for filtering the beat frequency signal output by the first optical comb generator.
[0036] In one optional implementation, the signal generation module 2 further includes a servo filter connected between the mixer and the oscillator for filtering the signal output by the mixer.
[0037] In one alternative implementation, Figure 2 This is a schematic diagram of the structure of a laser locking module in a signal analysis system according to an embodiment of the present invention, as shown below. Figure 2 As shown, the laser locking module 1 includes: a beam splitting unit 11, a locking unit 12, and a light extraction unit 13. The beam splitting unit 11 is connected to the locking unit 12 and the signal conversion module 3. The beam splitting unit 11 splits the initial optical signal into a first optical signal and a third optical signal. The first optical signal is output to the signal conversion module 3, and the third optical signal is output to the locking unit 12.
[0038] In one alternative implementation, Figure 3 This is a schematic diagram of the architecture of a laser locking module in a signal analysis system according to an embodiment of the present invention, as shown below. Figure 3As shown, the beam splitting unit 11 may include multiple beam splitting links and an optical combiner. The multiple beam splitting links include at least a first beam splitting link and a second beam splitting link. The first and second beam splitting links have the same structure, and the same components use the same parameter configuration. Specifically, the first beam splitting link includes a first laser and a first optical coupler. The first laser is connected to the first optical coupler, and the first output terminal of the first optical coupler is connected to the first input terminal of the optical combiner. The second beam splitting link includes a second laser and a second optical coupler. The second laser is connected to the second optical coupler, and the first output terminal of the second optical coupler is connected to the second input terminal of the optical combiner. The first and second optical couplers have the same beam splitting ratio. The output terminal of the optical combiner is connected to the locking unit 12, specifically to the resonator in the locking unit 12. An initial optical signal is generated by the first and second lasers, and then split by the corresponding optical couplers to obtain a first optical signal and a third optical signal. The third optical signal output from the first and second optical couplers is combined by the optical combiner and then input to the resonator in the locking unit 12.
[0039] In one optional implementation, the first and second optical couplers employ asymmetric beam splitting, for example, 90:10. Of the two optical signals obtained from the splitting, the one with a relatively higher splitting ratio is output as the first optical signal, and the one with a relatively lower splitting ratio is output as the third optical signal. Since the splitting and output process of the first optical signal does not involve a resonator, the modulation operation of the resonator will not interfere with the stability of the first and second lasers, thereby reducing noise in the first optical signal and avoiding the introduction of noise interference when using the first optical signal to carry the radio frequency signal under test.
[0040] In one alternative implementation, such as Figure 3 As shown, the locking unit 12 includes a resonator. The third optical signal is input into the resonator, which can be a high-Q resonator, such as a TFLN microring or a crystal resonator. Narrow-linewidth self-injection locking is achieved by feeding Rayleigh scattered light back to the laser. After being combined by an optical combiner, the third optical signal is input into the resonator. Through the self-injection locking effect, the frequencies of the first and second lasers are locked to two different but adjacent longitudinal modes within the resonator cavity. Since they share the same physical cavity, the resonator's response to environmental disturbances, such as temperature fluctuations or vibrations, acts simultaneously and equally on the frequencies of the optical signals output by the first and second lasers. This results in a high correlation between the frequency effects of the first and second laser outputs. During the beat frequency conversion process in the subsequent signal conversion module 3, this common-mode noise is canceled out, thus ensuring high stability of the beat frequency center frequency.
[0041] In one alternative implementation, such as Figure 2As shown, the light extraction unit 13 is connected in the feedback loop between the resonator and the beam splitting unit 11, and is also connected to the first optical comb spectrum generator. Specifically, as... Figure 3 As shown, the optical extraction unit 13 consists of multiple spaced-apart optical couplers and optical isolators. It extracts and isolates the optical signal fed back from the feedback loop through these spaced-apart optical couplers and isolators to obtain a second optical signal. For example, in... Figure 3 In the example shown, the optical extraction unit 13 is composed of two optical couplers (a third optical coupler and a first optical coupler) and one optical isolator (a first optical isolator) connected at intervals. The third optical coupler is connected in the feedback loop between the resonator and the beam splitter 11, specifically in the feedback loop between the resonator and the optical combiner. The optical signal fed back from the feedback loop is extracted layer by layer through the third and fourth optical couplers, and the optical signal is isolated by the first optical isolator. It should be noted that... Figure 3 The number of optical couplers and optical isolators included in the light extraction unit 13 shown is only an example and can be adjusted according to requirements in actual use.
[0042] In one alternative implementation, such as Figure 3 As shown, the locking unit 12 also includes a second photodetector and a control unit. The second photodetector is connected to the optical coupler that outputs the second optical signal in the light extraction unit 13, i.e., to the last stage optical coupler. The second photodetector is used to detect the output power of the light extraction unit 13. The control unit is connected to the resonator and the second photodetector respectively. The control unit is used to adjust the operating parameters of the resonator based on the output power detected by the second photodetector. Adjusting the operating parameters of the resonator may include adjusting the drive current and phase of the resonator to ensure the stability of the self-injection locking.
[0043] In one alternative implementation, such as Figure 3 As shown, the control unit is also connected to the first laser and the second laser in the beam splitting unit 11. The control unit is also used to adjust the operating parameters of the first laser and the second laser in the beam splitting unit 11 based on the output power detected by the second photodetector. The adjustment of the operating parameters of the first laser and the second laser may include adjusting the optical power of the first laser and the second laser to ensure the stability of the self-injection locking.
[0044] In one optional implementation, the signal conversion module 3 includes at least one signal conversion link. Figure 4 This is a schematic diagram of the signal conversion link in a signal analysis system according to an embodiment of the present invention, such as... Figure 4As shown, the signal conversion link includes a modulator, a second optical comb generator, and a third photodetector, which are connected sequentially. Specifically, a first optical signal and the radio frequency signal under test (RF signal) are input to the modulator. The first optical signal serves as an optical carrier and is modulated with the RF signal under test input to the modulator to achieve electro-optical conversion of the RF signal under test. A driving signal is input to the second optical comb generator to drive it to further convert the converted RF signal under test into a beat frequency signal. The third photodetector performs photoelectric conversion on the beat frequency signal corresponding to the RF signal under test, converting it into an electrical signal.
[0045] In one alternative implementation, the signal conversion link further includes an optical amplifier connected between the modulator and the second optical comb generator. The optical amplifier is used to amplify the optical signal output by the modulator to increase the signal power.
[0046] In one alternative implementation, the signal conversion link further includes an optical filter connected between the second optical comb generator and the third photodetector. The optical filter is used to filter the beat frequency signal output by the second optical comb generator.
[0047] In one optional implementation, the signal conversion link further includes an electrical filter and a gain unit. The third photodetector, the electrical filter, and the gain unit are connected in sequence. The electrical filter is used to filter the electrical signal of the beat frequency signal output by the third photodetector. The gain unit is used to increase and amplify the signal strength of the electrical signal of the beat frequency signal output by the third photodetector, so as to facilitate the detection and analysis of the electrical signal of the beat frequency signal corresponding to the radio frequency signal under test by the signal processing module 4.
[0048] In an optional implementation, if the signal conversion module 3 includes a signal conversion link, the first output terminal of the first optical coupler or the first output terminal of the second optical coupler in the laser locking module 1 is connected to the modulator, outputting a first optical signal to the modulator. Simultaneously, in the first and second optical couplers, the optical coupler that outputs the first optical signal to the modulator is also connected to the modulator via an optical isolator, for example, such as... Figure 3 As shown, the first optical coupler is also connected to the second optical isolator. The first optical signal output from the first optical coupler is output to the modulator after passing through the second optical isolator. Alternatively, the second optical coupler is also connected to the third optical isolator. The first optical signal output from the second optical coupler is output to the modulator after passing through the third optical isolator. The first optical signal is transmitted unidirectionally to the modulator through the second or third optical isolator, avoiding reflection interference of the optical signal.
[0049] In an optional implementation, if the signal conversion module 3 includes multiple signal conversion links, the signal conversion links included in the signal conversion module 3 correspond one-to-one with the beam splitting links included in the laser locking module 1; the first output terminal of the optical coupler in the beam splitting link of the laser locking module 1 is connected to the modulator in the corresponding signal conversion link, and outputs a first optical signal to the modulator in the corresponding signal conversion link. Simultaneously, in each beam splitting link, an optical isolator is connected between the optical coupler and the corresponding modulator, for example, such as... Figure 3 As shown, the first optical coupler is also connected to the second optical isolator. The first optical signal output from the first optical coupler is output to the modulator after passing through the second optical isolator. The second optical coupler is also connected to the third optical isolator. The first optical signal output from the second optical coupler is output to the modulator after passing through the third optical isolator. The unidirectional transmission of the first optical signal to the modulator is achieved through the second and third optical isolators, avoiding reflection interference. In the multi-signal conversion link and beam splitting link modes, the same resonant cavity provides two optical carriers, meaning the two first optical signals provide a strictly consistent frequency reference. Combined with the shared drive signal for the entire system, this ensures the coherence of the RF signal in the two optoelectronic conversion links. Furthermore, since the spontaneous emission of photons and the relative intensity noise of the dual lasers originate from their respective independent gain media, their broadband quantum noise is physically independent. Therefore, it can suppress the shot noise of the detector and the broadband quantum noise of the light source, thereby obtaining a cleaner detection background.
[0050] In one alternative implementation, Figure 5 This is a schematic diagram of the structure of the signal processing module in the signal analysis system according to an embodiment of the present invention, such as... Figure 5 As shown, the signal processing module 4 includes at least one analog-to-digital converter (ADC), a clock control unit, and a digital signal processing unit (DSP). The ADC is connected to both the ADC and the DSP. The clock control unit is connected to the signal generation module 2. The clock control unit converts the drive signal generated by the signal generation module 2 into a clock signal. Specifically, it uses a low-jitter frequency divider to convert the drive signal into a sampling clock adapted to the sampling rate of the ADC and a logic clock adapted to the DSP, thereby ensuring strict time-domain alignment between optical sampling and electrical quantization and eliminating measurement errors caused by photoelectric clock slippage.
[0051] In one optional implementation, the analog-to-digital converter included in the signal processing module 4 corresponds one-to-one with the signal conversion link included in the signal conversion module 3, and the analog-to-digital converter is connected to the third photodetector of the corresponding signal conversion link.
[0052] In one optional implementation, if the signal conversion module 3 contains only one signal conversion link, the digital signal processing unit directly performs Fast Fourier Transform and demodulation on the signal input from the analog-to-digital converter to form measurement data. This measurement data is then used for signal analysis to obtain the final analysis result. If the signal conversion module 3 includes multiple signal conversion links, the digital signal processing unit performs cross-correlation operations on the multiple input signals to obtain the final analysis result.
[0053] In one optional implementation, the signal analysis system further includes an RF conditioning module, and the signal processing module 4 further includes a digital-to-analog converter (DAC). The DAC is connected to both the digital signal processing unit and the RF conditioning module. The digital signal processing unit analyzes the sampled signal of the beat frequency signal input to the DAC and outputs a reference signal for the RF signal under test. The DAC converts the reference signal into an analog signal, enabling the RF conditioning module to condition and self-calibrate the RF signal under test based on the reference signal obtained from the detection and extraction of the RF signal. The RF conditioning module is connected to the signal conversion module 3, and performs self-calibration on the RF signal under test based on the analog reference signal output by the DAC, thereby forming a closed-loop self-test circuit.
[0054] The signal analysis system provided in this embodiment of the invention uses a laser locking module to split the initial optical signal into a first optical signal and a second optical signal. The first optical signal is modulated with the radio frequency signal under test, and the second optical signal is used to generate a driving signal. Simultaneously, in the signal generation module, the first optical comb spectrum generator, the first photodetector, the mixer, and the oscillator are linked in a closed loop to form an optical phase-locked loop, generating a stable driving signal. The driving signal drives the signal conversion module and the signal processing module, thereby achieving absolute phase synchronization of the optical carrier and the optical frequency comb local oscillator within the signal analysis system, that is, achieving source synchronization of the signal analysis system. This eliminates frequency errors caused by temperature drift, improves the accuracy of detection and extraction of radio frequency microwave signals, and thus enhances the signal analysis capability of radio frequency microwave signals.
[0055] According to an embodiment of the present invention, a signal analysis method embodiment is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.
[0056] This embodiment provides a signal analysis method that can be used in the signal analysis system described above. Figure 6 This is a flowchart illustrating a signal analysis method according to an embodiment of the present invention, as shown below. Figure 6 As shown, the process includes the following steps: In step S601, in response to the input of the radio frequency signal to be tested, the first optical signal and the radio frequency signal to be tested are input to the signal conversion module 3, and the signal conversion module 3 is driven to perform signal conversion on the radio frequency signal to be tested based on the driving signal output by the signal generation module 2, so as to obtain the beat frequency signal corresponding to the radio frequency signal to be tested.
[0057] In this embodiment of the invention, the first optical signal is obtained by splitting the initial optical signal based on the laser locking module 1. The first optical signal is used to modulate the radio frequency signal under test. The first optical signal and the radio frequency signal under test are input to the modulator of the signal conversion module 3 for modulation to obtain the optical signal corresponding to the radio frequency signal under test. The second optical comb generator of the signal conversion module 3 is driven by the driving signal to convert the optical signal corresponding to the radio frequency signal under test into the corresponding beat frequency signal. Based on the third photodetector of the signal conversion module 3, the beat frequency signal corresponding to the radio frequency signal under test is converted into the corresponding electrical signal.
[0058] Step S602: Based on the signal processing module 4, the beat frequency signal corresponding to the radio frequency signal under test is processed and analyzed to obtain the analysis result of the radio frequency signal under test.
[0059] In this embodiment of the invention, the beat frequency signal corresponding to the radio frequency signal under test is converted into a corresponding digital signal based on the analog-to-digital converter in the signal processing module 4. Based on the digital signal processing unit in the signal processing module 4, the digital signal corresponding to the radio frequency signal under test is processed to obtain the analysis result of the radio frequency signal under test.
[0060] In one optional implementation, if the signal conversion module 3 contains only one signal conversion link, meaning there is only one beat frequency signal input to the signal processing module 4, the digital signal processing unit directly performs Fast Fourier Transform and demodulation on the signal input to the analog-to-digital converter to form measurement data. Then, signal analysis is performed on the measurement data to obtain the final analysis result. If the signal conversion module 3 includes multiple signal conversion links, meaning there are multiple beat frequency signals input to the signal processing module 4, the digital signal processing unit performs cross-correlation operations on the multiple input signals to obtain the final analysis result.
[0061] In one optional implementation, cross-correlation calculations are performed on the multiple signals input to the digital signal processing unit as follows: Within each clock cycle of the digital signal processing unit, the multiple input signals are multiplied, the results of the multiplications are accumulated, and the average value is calculated to obtain the power analysis result of the RF signal under test. During this process, since the average value of the product of uncorrelated noise fluctuates around zero, the amplitude of this fluctuation is the residual noise. The magnitude of the residual noise is inversely proportional to time; therefore, the residual noise decreases as the detection time increases. Thus, by increasing the detection and calculation time, the residual noise floor is reduced, improving the accuracy of the analysis of the RF signal under test.
[0062] The signal analysis method provided in this invention modulates the first optical signal output by the laser locking module and the radio frequency signal under test, generates a driving signal based on the second optical signal output by the laser locking module, and uses the driving signal to drive the signal conversion of the radio frequency signal under test and the signal processing of the beat frequency signal corresponding to the radio frequency signal under test. This achieves absolute phase synchronization of the optical carrier and the local oscillator of the optical frequency comb within the signal analysis system, i.e., source synchronization of the signal analysis system. This eliminates frequency errors caused by temperature drift, improves the accuracy of detection and extraction of radio frequency microwave signals, and thus enhances the signal analysis capability of radio frequency microwave signals.
[0063] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.
Claims
1. A signal analysis system, characterized in that, The system includes: a laser locking module (1), a signal generation module (2), a signal conversion module (3), and a signal processing module (4); The laser locking module (1) is connected to the signal generation module (2) and the signal conversion module (3); the laser locking module (1) is used to split the initial optical signal into a first optical signal and a second optical signal, wherein the first optical signal is output to the signal conversion module (3) and modulated with the radio frequency signal to be tested input to the signal conversion module (3) to lock the initial optical signal, and is simultaneously output to the signal generation module (2). The signal generation module (2) includes a first optical comb generator, a first photodetector, a mixer, and an oscillator. The first optical comb generator, the first photodetector, the mixer, and the oscillator form a closed-loop connection. The laser locking module (1) is connected to the first optical comb generator and inputs the second optical signal into the first optical comb generator. The reference signal corresponding to the second optical signal is input into the mixer. The oscillator is connected to the signal conversion module (3) and the signal processing module (4) respectively and outputs driving signals to the signal conversion module (3) and the signal processing module (4) respectively. The signal conversion module (3) is connected to the signal processing module (4).
2. The system according to claim 1, characterized in that, The laser locking module (1) includes: a beam splitting unit (11), a locking unit (12), and a light extraction unit (13). The beam splitting unit (11) is connected to the locking unit (12) and the signal conversion module (3). The beam splitting unit (11) splits the initial optical signal into a first optical signal and a third optical signal. The first optical signal is output to the signal conversion module (3), and the third optical signal is output to the locking unit (12). The locking unit (12) includes a resonator, and the third optical signal is input into the resonator; The light extraction unit (13) is connected in the feedback loop between the resonator and the beam splitting unit (11) and is connected to the first optical comb generator. The light extraction unit (13) consists of multiple spaced optical couplers and optical isolators. The optical signal fed back in the feedback loop is extracted and isolated by the multiple spaced optical couplers and optical isolators to obtain the second optical signal.
3. The system according to claim 2, characterized in that, The beam splitting unit (11) includes: multiple beam splitting links and an optical combiner, wherein the multiple beam splitting links include at least a first beam splitting link and a second beam splitting link; The first beam splitting link includes a first laser and a first optical coupler. The first laser is connected to the first optical coupler, and the first output terminal of the first optical coupler is connected to the first input terminal of the optical combiner. The second beam splitting link includes a second laser and a second optical coupler. The second laser is connected to the second optical coupler. The first output terminal of the second optical coupler is connected to the second input terminal of the optical combiner. The first optical coupler and the second optical coupler have the same beam splitting ratio. The output end of the optical combiner is connected to the locking unit (12).
4. The system according to claim 2, characterized in that, The locking unit (12) also includes a second photodetector and a control unit; The second photodetector is connected to the optical coupler that outputs the second optical signal in the light extraction unit (13), and the second photodetector is used to detect the output power of the light extraction unit (13). The control unit is connected to the resonator and the second photodetector respectively. The control unit is used to adjust the operating parameters of the resonator based on the output power detected by the second photodetector.
5. The system according to claim 4, characterized in that, The control unit is also connected to the first laser and the second laser in the beam splitting unit (11), and the control unit is also used to adjust the operating parameters of the first laser and the second laser in the beam splitting unit (11) based on the output power detected by the second photodetector.
6. The system according to claim 1, characterized in that, The signal conversion module (3) includes at least one signal conversion link, which includes a modulator, a second optical comb generator and a third photodetector, wherein the modulator, the second optical comb generator and the third photodetector are connected in sequence. The first optical signal and the radio frequency signal under test are input to the modulator, and the driving signal is input to the second optical comb generator to drive the second optical comb generator to work.
7. The system according to claim 3 or 6, characterized in that, If the signal conversion module (3) includes a signal conversion link, the first output terminal of the first optical coupler or the first output terminal of the second optical coupler in the laser locking module (1) is connected to the modulator to output the first optical signal to the modulator.
8. The system according to claim 3 or 6, characterized in that, If the signal conversion module (3) includes multiple signal conversion links, the signal conversion links included in the signal conversion module (3) correspond one-to-one with the beam splitting links included in the laser locking module (1); The first output terminal of the optical coupler in the beam splitting link of the laser locking module (1) is connected to the modulator in the corresponding signal conversion link, and outputs the first optical signal to the modulator in the corresponding signal conversion link.
9. The system according to claim 1, characterized in that, The signal processing module (4) includes at least one analog-to-digital converter, a clock control unit, and a digital signal processing unit; The at least one analog-to-digital converter is connected to the digital signal processing unit and the digital signal processing unit, respectively. The clock control unit is connected to the signal generation module (2), and the clock control unit is used to convert the driving signal generated by the signal generation module (2) into a clock signal.
10. The system according to claim 9, characterized in that, The system also includes a radio frequency conditioning module, and the signal processing module (4) further includes a digital-to-analog converter; The digital-to-analog converter is connected to the digital signal processing unit and the radio frequency conditioning module. The digital-to-analog converter is used to convert the reference signal of the radio frequency signal under test output by the digital signal processing unit into an analog reference signal and output it to the radio frequency conditioning module. The radio frequency conditioning module is connected to the signal conversion module (3). The radio frequency conditioning module is used to perform self-calibration on the radio frequency signal under test based on the analog reference signal output by the digital-to-analog converter.
11. The system according to claim 6 or 9, characterized in that, The analog-to-digital converter included in the signal processing module (4) corresponds one-to-one with the signal conversion link included in the signal conversion module (3), and the analog-to-digital converter is connected to the third photodetector of the corresponding signal conversion link.
12. A signal analysis method, characterized in that, Applied to the signal analysis system as described in any one of claims 1-11, the method comprises: In response to the input of the radio frequency signal to be tested, the first optical signal and the radio frequency signal to be tested are input to the signal conversion module (3), and the signal conversion module (3) is driven to perform signal conversion on the radio frequency signal to be tested based on the driving signal output by the signal generation module (2) to obtain the beat frequency signal corresponding to the radio frequency signal to be tested. The first optical signal is obtained by splitting the initial optical signal based on the laser locking module (1), and the first optical signal is used to perform signal modulation with the radio frequency signal to be tested. Based on the signal processing module (4), the beat frequency signal corresponding to the radio frequency signal under test is processed and analyzed to obtain the analysis result of the radio frequency signal under test.
13. The method according to claim 12, characterized in that, The step of inputting the first optical signal and the radio frequency signal under test into the signal conversion module (3), and driving the signal conversion module (3) to perform signal conversion on the radio frequency signal under test based on the driving signal output by the signal generation module (2) to obtain the beat frequency signal corresponding to the radio frequency signal under test, includes: The modulator of the input signal conversion module (3) that converts the first optical signal and the radio frequency signal under test is modulated to obtain the optical signal corresponding to the radio frequency signal under test; The second optical comb generator of the signal conversion module (3) is driven by the driving signal to work and convert the optical signal corresponding to the radio frequency signal under test into the corresponding beat frequency signal. Based on the third photodetector of the signal conversion module (3), the beat frequency signal corresponding to the radio frequency signal to be tested is converted into an electrical signal.
14. The method according to claim 12, characterized in that, The signal processing module (4) processes and analyzes the beat frequency signal corresponding to the radio frequency signal under test to obtain the analysis result of the radio frequency signal under test, including: Based on the analog-to-digital converter in the signal processing module (4), the beat frequency signal corresponding to the radio frequency signal under test is converted into the corresponding digital signal; Based on the digital signal processing unit in the signal processing module (4), the digital signal corresponding to the radio frequency signal under test is processed to obtain the analysis result of the radio frequency signal under test.