Microwave photonics system and method for frequency and angle of arrival nanosecond-level measurements

Abstract

This invention relates to the field of radio frequency signal measurement technology, and proposes a microwave photonic system and method for nanosecond-level measurement of frequency and angle of arrival. The system includes: an optical frequency comb generation module, in which a narrow-linewidth laser generated by a tunable laser is amplified by an erbium-doped fiber amplifier and then excited by the Kerr nonlinear effect to generate a coherent optical frequency comb; an antenna receiving module, which receives a first radio frequency signal and a second radio frequency signal; an electro-optic modulation module, in which the first radio frequency signal and the second radio frequency signal are respectively input to a first sub-modulator and a second sub-modulator, and a third sub-modulator is used to combine the first and second modulated lights and introduce a preset phase difference to obtain a target optical pulse signal; and a frequency-time mapping and detection module, in which the target optical pulse signal is frequency-time mapped via a dispersive fiber, a photodetector converts the mapped optical signal into an electrical pulse train, and an oscilloscope is used to observe the time interval between adjacent peaks and the pulse amplitude information of the electrical pulse train to obtain the characteristic parameters of the radio frequency signal.

Description

Technical Field

[0001] This invention relates to the field of radio frequency signal measurement technology, and in particular to a microwave photonic system and method for measuring frequency and angle of arrival at the nanosecond level. Background Technology

[0002] In modern radar, electronic reconnaissance, cognitive radio and other fields, the measurement of the angle of arrival and frequency of radio frequency signals is a core requirement for achieving target perception and signal recognition. Microwave photonic measurement technology has become an important development direction in this field due to its advantages such as ultra-wideband and resistance to electromagnetic interference.

[0003] Traditional radio frequency (RF) angle-of-arrival (AOA) measurement techniques (such as digital beamforming and phase interferometry) are limited by the performance of electronic devices and are difficult to adapt to the measurement requirements of high carrier frequency and ultra-wideband scenarios. Microwave photonics measurement technology breaks through the bottleneck of traditional electronic technology by processing RF signals in the optical domain, but existing microwave photonics systems that combine frequency and AOA measurement functions still have significant drawbacks: First, the real-time performance is insufficient. Existing systems mostly rely on mode-locked lasers for signal processing, and the measurement resolution can only reach the microsecond level, which cannot meet the requirements for rapid capture of transient signals. Some solutions also need to calculate the measurement results through a complex digital back-calculation process, which further reduces the response efficiency. Second, the system is complex and unstable. Some solutions require two strictly matched opposite dispersion fiber gratings, which increases the difficulty of implementation and system loss. Other solutions rely on components such as multi-channel photoelectric detection and voltage-controlled optical delay lines, which are easily affected by the external environment and introduce errors, resulting in a decrease in measurement accuracy. Third, the receiving sensitivity is limited. The inherent loss of key components makes the system unable to detect weak power signals, which limits its application scenarios in complex electromagnetic environments.

[0004] These shortcomings severely restrict the widespread application of microwave photonic measurement technology in demanding scenarios, and there is an urgent need for a frequency and angle of arrival synchronization measurement scheme that balances high real-time performance, high stability, and low complexity. Summary of the Invention

[0005] This invention provides a microwave photonics system and method for nanosecond-level measurement of frequency and angle of arrival, aiming to solve technical problems such as insufficient real-time performance, high system complexity, poor stability, and limited receiving sensitivity in related technologies.

[0006] In a first aspect, embodiments of the present invention provide a microwave photonic system for measuring frequency and angle of arrival at the nanosecond level, the system comprising: An optical frequency comb generation module includes a tunable laser, an erbium-doped fiber amplifier, and a silicon nitride microring. The narrow linewidth laser generated by the tunable laser is amplified by the erbium-doped fiber amplifier and then used as pump light coupled to the silicon nitride microring to excite the Kerr nonlinear effect and generate a coherent optical frequency comb. The antenna receiving module includes a first antenna array element and a second antenna array element, used to receive a first radio frequency signal and a second radio frequency signal; The electro-optic modulation module is a dual parallel Mach-Zehnder modulator, including a first sub-modulator, a second sub-modulator and a third sub-modulator. The first radio frequency signal and the second radio frequency signal are respectively input to the first sub-modulator and the second sub-modulator to generate the first modulated light and the second modulated light with the minimum bias point. The third sub-modulator is used to merge the first modulated light and the second modulated light and introduce a preset phase difference to obtain the target light pulse signal. The frequency-time mapping and detection module includes a dispersive optical fiber, a photodetector, and an oscilloscope. The target optical pulse signal is frequency-time mapped via the dispersive optical fiber. The photodetector converts the mapped optical signal into an electrical pulse train. The oscilloscope is used to observe the time interval between adjacent peaks and the pulse amplitude information of the electrical pulse train to obtain the characteristic parameters of the radio frequency signal. The characteristic parameters include at least frequency and angle of arrival information.

[0007] In one embodiment, optionally, the spacing between the first antenna element and the second antenna element is half the wavelength of the first or second radio frequency signal.

[0008] In one embodiment, optionally, the silicon nitride microring includes a high-Q silicon nitride integrated microring, the output frequency of the tunable laser matches the resonant mode of the silicon nitride microring, and the intracavity dispersion and nonlinear effects of the silicon nitride microring are balanced.

[0009] In one embodiment, optionally, the preset phase difference ranges from 0 < θ < π, which is used to extend the phase ambiguity test range from [-π / 2, π / 2] to [-π+θ, π-θ], eliminating angular ambiguity on both sides of the normal.

[0010] In one embodiment, optionally, the dispersion of the dispersive fiber satisfies the Talbot condition, such that the frequency of the radio frequency signal is linearly related to the time interval between adjacent peaks of the electrical pulse train.

[0011] In one embodiment, optionally, the optical frequency comb generation module further includes a programmable optical filter for spectral shaping of the coherent optical frequency comb and outputting light pulses with a preset repetition period.

[0012] In one embodiment, optionally, the oscilloscope includes a real-time oscilloscope for observing the time interval between adjacent peaks of the electrical pulse train to obtain the frequency of the radio frequency signal, and for inferring the phase difference between the first radio frequency signal and the second radio frequency signal by using the pulse amplitude information of adjacent peaks.

[0013] In a second aspect, embodiments of the present invention provide a method for measuring frequency and angle of arrival at the nanosecond level, used in the microwave photonic system described in any one of the first embodiments above, the method comprising: Narrow-linewidth laser light generated by a tunable laser is amplified by an erbium-doped fiber amplifier and used as pump light to couple to a silicon nitride microring, thereby exciting the Kerr nonlinear effect to generate a coherent optical frequency comb. The first antenna element and the second antenna element receive the first radio frequency signal and the second radio frequency signal respectively. The interval between the first antenna element and the second antenna element is half the wavelength of the radio frequency signal. The first radio frequency signal and the second radio frequency signal are respectively input into the first sub-modulator and the second sub-modulator of the dual parallel Mach-Zehnder modulator, and the coherent optical frequency comb is modulated with the minimum bias point. The first modulated light and the second modulated light generated by the third sub-modulator are combined and a preset phase difference is introduced to obtain the target light pulse signal. The target optical pulse signal is input into a dispersive fiber, and frequency-time mapping is achieved based on the Talbot effect. It is then converted into an electrical pulse train by a photodetector. The characteristic parameters of the radio frequency signal are obtained by observing the adjacent peak time interval and pulse amplitude information of the electrical pulse train using an oscilloscope, wherein the characteristic parameters include at least frequency and angle of arrival information.

[0014] In one embodiment, optionally, the phase difference between the first radio frequency signal and the second radio frequency signal is calculated using the following formula: φ=arcsin[(I + -I - ) / (2βI0)] Where φ represents the phase difference, I + I represents the pulse amplitude after introducing a positive phase shift. - I0 represents the pulse amplitude after introducing a negative phase shift, β represents the modulation depth of the RF signal on the modulator, and I0 represents the reference pulse amplitude without phase shift.

[0015] In one embodiment, optionally, the angle of arrival is calculated based on the relationship between the phase difference and the antenna element spacing, satisfying the following condition: φ=2πd sinα / λ Where λ represents the wavelength of the radio frequency signal, φ represents the phase difference, α represents the angle of arrival, and d represents the spacing between the antenna elements.

[0016] In one embodiment, optionally, the spacing between the first antenna element and the second antenna element is half the wavelength of the first or second radio frequency signal.

[0017] In one embodiment, optionally, the silicon nitride microring includes a high-Q silicon nitride integrated microring, the output frequency of the tunable laser matches the resonant mode of the silicon nitride microring, and the intracavity dispersion and nonlinear effects of the silicon nitride microring are balanced.

[0018] In one embodiment, optionally, the preset phase difference ranges from 0 < θ < π, which is used to extend the phase ambiguity test range from [-π / 2, π / 2] to [-π+θ, π-θ], eliminating angular ambiguity on both sides of the normal.

[0019] In one embodiment, optionally, the dispersion of the dispersive fiber satisfies the Talbot condition, such that the frequency of the radio frequency signal is linearly related to the time interval between adjacent peaks of the electrical pulse train.

[0020] In one embodiment, optionally, the optical frequency comb generation module further includes a programmable optical filter for spectral shaping of the coherent optical frequency comb and outputting light pulses with a preset repetition period.

[0021] In one embodiment, optionally, the oscilloscope includes a real-time oscilloscope for observing the time interval between adjacent peaks of the electrical pulse train to obtain the frequency of the radio frequency signal, and for inferring the phase difference between the first radio frequency signal and the second radio frequency signal by using the pulse amplitude information of adjacent peaks.

[0022] In the above technical solution, a coherent optical frequency comb is generated by exciting the Kerr nonlinear effect through a high-Q silicon nitride microring. Combined with the Talbot effect of dispersive fiber, a linear mapping from the radio frequency signal frequency to the time interval of the electrical pulse is achieved. This breaks through the microsecond-level measurement bottleneck caused by the reliance on mode-locked lasers in existing systems, achieving nanosecond-level time resolution and significantly improving the ability to capture transient signals. By using dual-path modulation and phase difference introduction design with dual parallel Mach-Zehnder modulators, not only is the unambiguous phase test range expanded, effectively eliminating the ambiguity problem of the angle of arrival on both sides of the normal, but the phase difference of the radio frequency signal is also directly inferred from the pulse amplitude information of the electrical pulse, avoiding the real-time loss caused by the complex digital inference process. At the same time, the system uses a single dispersive fiber to achieve frequency-time mapping, without the need for strictly matched opposite dispersive gratings, and the core components are highly integrated, which greatly reduces the system implementation difficulty and inherent loss, improves the receiving sensitivity of weak power signals, and enhances the system's miniaturization integration potential and adaptability to complex electromagnetic environments while ensuring measurement accuracy and stability. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic block diagram of a microwave photonic system for measuring frequency and angle of arrival in nanoseconds according to an embodiment of the present invention is shown.

[0025] Figure 2 A flowchart of a method for measuring the frequency and angle of arrival of a radio frequency signal according to an embodiment of the present invention is shown. Detailed Implementation

[0026] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0028] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0029] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] Please see Figure 1 , Figure 1 A schematic block diagram of a microwave photonic system for measuring frequency and angle of arrival in nanoseconds according to an embodiment of the present invention is shown.

[0031] like Figure 1 As shown, this embodiment of the invention provides a microwave photonics system for measuring frequency and angle of arrival at the nanosecond level. The system includes: The optical frequency comb generation module 11 includes a tunable laser 111, an erbium-doped fiber amplifier 112, and a silicon nitride microring 113. The narrow linewidth laser generated by the tunable laser 111 is amplified by the erbium-doped fiber amplifier 112 and then used as pump light coupled to the silicon nitride microring 113 to excite the Kerr nonlinear effect and generate a coherent optical frequency comb.

[0032] In one embodiment, optionally, the silicon nitride microring 113 includes a high-Q silicon nitride integrated microring, the output frequency of the tunable laser matches the resonant mode of the silicon nitride microring, and the intracavity dispersion and nonlinear effects of the silicon nitride microring are balanced.

[0033] Coherent optical frequency comb: A spectrum composed of a series of coherent light pulses with equal frequency intervals and phase lock, it is the core light source for achieving accurate measurement of high-frequency signals.

[0034] Kerr nonlinearity: a nonlinear optical phenomenon caused by the change in refractive index with light intensity when light propagates in a medium, which can be used to generate broadband optical combs.

[0035] A tunable laser first generates a monochromatic, narrow-linewidth laser beam. After its power is boosted by an erbium-doped fiber amplifier, it is used as pump light and coupled to a silicon nitride microring via a tapered fiber. When the laser frequency precisely matches the resonant mode of the microring, and the intracavity dispersion and Kerr nonlinearity are balanced, a broadband, coherent, low-noise optical frequency comb is generated. The spacing of the comb teeth is determined by the free spectral range of the microring. If a programmable optical filter is configured, the frequency comb can be further spectrally shaped to output optical pulses with a fixed repetition period, adapting to subsequent modulation requirements.

[0036] Compared to existing technologies that rely on mode-locked lasers, the optical frequency comb generated by silicon nitride microrings has the advantages of ultra-wideband, high repetition rate, and low loss, providing core support for nanosecond-level measurements; the high Q value and mode-matching design ensure the stability of the optical frequency comb and avoid frequency drift from affecting measurement accuracy.

[0037] The antenna receiving module 12 includes a first antenna array element 121 and a second antenna array element 122, and is used to receive a first radio frequency signal and a second radio frequency signal.

[0038] In one embodiment, optionally, the spacing between the first antenna element and the second antenna element is half the wavelength of the first or second radio frequency signal.

[0039] Antenna array element: The core sensing unit used to receive spatial radio frequency signals, which must meet the spacing requirements that are adapted to the wavelength of the target radio frequency signal.

[0040] The antenna receiving module comprises two identical antenna elements, with the distance between them set to half the wavelength of the target radio frequency signal. This distance is an optimized choice based on the propagation characteristics of electromagnetic waves, ensuring a linear relationship between the phase difference and the angle of arrival of the two received signals, providing a precise physical basis for subsequent phase difference-based angle of arrival calculation. During operation, the two elements synchronously receive the same radio frequency signal in space, outputting a first radio frequency signal and a second radio frequency signal to the electro-optic modulation module, respectively.

[0041] In this way, the half-wavelength spacing design eliminates the nonlinear interference between the phase difference and the angle of arrival, ensuring the accuracy of the angle of arrival measurement; the dual-element synchronous receiving mode provides two signals from the same source and comparable for subsequent interferometric modulation, which is a prerequisite for realizing the angle of arrival measurement; the simple structure and absence of complex auxiliary components reduce the overall system loss and failure rate.

[0042] The electro-optic modulation module 13 is a dual parallel Mach-Zehnder modulator, including a first sub-modulator 131, a second sub-modulator 132, and a third sub-modulator 133. The first radio frequency signal and the second radio frequency signal are respectively input to the first sub-modulator 131 and the second sub-modulator 132, and modulated at the minimum bias point to generate a first modulated light and a second modulated light. The third sub-modulator 133 is used to merge the first modulated light and the second modulated light and introduce a preset phase difference to obtain a target light pulse signal. In one embodiment, optionally, the value range of the preset phase difference is 0 < θ < π, which is used to extend the phase ambiguity test range from [-π / 2, π / 2] to [-π+θ, π-θ] to eliminate the ambiguity of the arrival angle on both sides of the normal.

[0043] Dual Parallel Mach-Zehnder Modulator (DPMZM): An integrated optical device consisting of two parallel sub-modulators (signal modulation) and a master modulator (beam combining + phase control), which can realize independent modulation and coordinated control of two signals.

[0044] Minimum bias point: The operating point where the modulator output light intensity is linearly related to the RF signal amplitude, which can avoid signal distortion.

[0045] Preset phase difference: A fixed phase offset applied by a third sub-modulator to extend the phase measurement range.

[0046] The first and second sub-modulators operate at their minimum bias points, receiving two radio frequency (RF) signals respectively and linearly modulating the optical frequency comb to generate first and second modulated beams carrying RF signal information. Subsequently, the third sub-modulator combines the two modulated beams and introduces a preset phase difference with a value in the range of 0 < θ < π. Finally, it outputs a target optical pulse signal containing frequency and phase difference information. The entire process maps the RF signal characteristics (frequency and phase difference) in the electrical domain to the optical domain through electro-optical conversion.

[0047] Minimum bias modulation ensures a linear mapping between the RF signal and the modulated light intensity, avoiding measurement errors caused by signal distortion; the preset phase difference introduced by the third sub-modulator extends the unambiguous phase test range from [-π / 2, π / 2] to [-π+θ, π-θ], completely solving the industry pain point of ambiguity at the angle of arrival on both sides of the normal; the dual parallel integrated design reduces the connection loss between devices, improves modulation efficiency and system stability, and significantly reduces structural complexity compared to multi-channel discrete modulation schemes.

[0048] The frequency-time mapping and detection module 14 includes a dispersive fiber 141, a photodetector 142, and an oscilloscope 143. The target optical pulse signal is frequency-time mapped via the dispersive fiber 141. The photodetector 142 converts the mapped optical signal into an electrical pulse train. The oscilloscope 143 is used to observe the time interval between adjacent peaks and the pulse amplitude information of the electrical pulse train to obtain the characteristic parameters of the radio frequency signal. The characteristic parameters include at least frequency and angle of arrival information.

[0049] In one embodiment, optionally, the dispersion of the dispersive fiber 141 satisfies the Talbot condition, such that the frequency of the radio frequency signal is linearly related to the time interval between adjacent peaks of the electrical pulse train.

[0050] In one embodiment, optionally, the optical frequency comb generation module 11 further includes a programmable optical filter for spectral shaping of the coherent optical frequency comb and outputting light pulses with a preset repetition period.

[0051] Frequency-time mapping: Based on the Talbot effect, the frequency information of optical signals is converted into pulse interval information in the time domain, enabling indirect frequency measurement.

[0052] The Tabor condition: The specific conditions that the dispersion of a dispersive fiber must meet to ensure a strict linear correspondence between frequency and pulse interval.

[0053] Real-time oscilloscope: An oscilloscope with a high sampling rate and high bandwidth, capable of capturing the time-domain characteristics (interval, amplitude) of electrical pulse trains in real time.

[0054] In one embodiment, optionally, the oscilloscope 143 includes a real-time oscilloscope for observing the time interval between adjacent peaks of the electrical pulse train to obtain the frequency of the radio frequency signal, and for inferring the phase difference between the first radio frequency signal and the second radio frequency signal by using the pulse amplitude information of adjacent peaks.

[0055] The target optical pulse signal is input into the dispersive fiber. When the fiber dispersion satisfies the Talbot condition, different frequency components of the optical frequency comb will produce different delays, realizing a linear mapping from frequency to time interval. Subsequently, the photodetector converts the mapped optical signal into an electrical pulse train, restoring the optical domain information into an observable signal in the electrical domain. Finally, the time interval between adjacent peaks (corresponding to the frequency) and the amplitude difference (corresponding to the phase difference) of the electrical pulse train are observed by a real-time oscilloscope, and the frequency and angle of arrival of the radio frequency signal are finally deduced.

[0056] The frequency-time mapping achieved by the Talbot effect avoids complex digital signal processing, directly obtaining the frequency through time-domain intervals. Combined with the high sampling rate of a real-time oscilloscope, frequency measurement achieves nanosecond-level resolution, breaking through the microsecond-level bottleneck of existing mode-locked laser solutions. The combination of photoelectric detection and oscilloscope observation enables real-time visualization of signal characteristics without the need for complex reverse calculation processes, improving the real-time performance of measurements. The linear mapping relationship ensures the accuracy of frequency measurement, and the method of inferring the phase difference from the amplitude difference simplifies the logic of angle of arrival calculation, further reducing system latency.

[0057] like Figure 2 As shown, in a second aspect, a method for measuring frequency and angle of arrival at the nanosecond level is provided for the microwave photonic system described in any of the first embodiments above, the method comprising: Step S200: Under the preset reference incident conditions (when the radio frequency signal arrival angle is 0 degrees), measure the amplitude value of the electrical pulse train as the reference pulse amplitude parameter (corresponding to Vref in the formula). Step S201: The narrow linewidth laser generated by the tunable laser is amplified by an erbium-doped fiber amplifier and used as pump light to couple to a silicon nitride microring to excite the Kerr nonlinear effect and generate a coherent optical frequency comb. Step S202: The first radio frequency signal and the second radio frequency signal are received by the first antenna array element and the second antenna array element respectively. The interval between the first antenna array element and the second antenna array element is half the wavelength of the radio frequency signal. Step S203: The first radio frequency signal and the second radio frequency signal are respectively input into the first sub-modulator and the second sub-modulator of the dual parallel Mach-Zehnder modulator to modulate the coherent optical frequency comb with the minimum bias point. The first modulated light and the second modulated light generated by the third sub-modulator are combined and a preset phase difference is introduced to obtain the target light pulse signal. Step S204: Input the target optical pulse signal into a dispersive fiber, realize frequency-time mapping based on the Talbot effect, and convert it into an electrical pulse train through a photodetector; Step S205: Observe the adjacent peak time interval and pulse amplitude information of the electrical pulse train using an oscilloscope, and combine them with the reference pulse amplitude parameter to obtain the characteristic parameters of the radio frequency signal, wherein the characteristic parameters include at least frequency and angle of arrival information.

[0058] In the above technical solution, firstly, the tunable laser, after being amplified, is coupled into an optical microring as pump light. When the laser frequency is precisely matched to a certain resonant mode of the silicon nitride microring, and the intracavity dispersion and nonlinear effects are balanced, a coherent, low-noise, stable optical frequency comb can be output. Then, the optical frequency comb is spectrally shaped using a programmable optical filter, and the electric field intensity of the output light pulse can be approximately expressed as: , Let represent the Dirac function, and T be the repetition period of the optical pulse. Assuming the distance between the two antenna elements is half the wavelength of the radio frequency signal, the two received radio frequency signals can be expressed as follows: , ωRF represents the radio frequency angular frequency received by the antenna. Let be the phase difference between the two radio frequency signals. After passing through a dual parallel Mach-Zehnder modulator, the electric field strength of the output sampled optical signal can be expressed as: , Both sub-modulators operate at their minimum bias points, β is the modulation depth of the RF signal on the two sub-modulators, and θ is the phase difference introduced by sub-modulator 3 for the two modulated optical signals. After passing through a dispersive fiber, and with the fiber dispersion satisfying... Given the Talbot condition, the output photocurrent after the photodetector beats can be expressed as: , Therefore, by sampling the pulses in the time domain and reading their time intervals, the frequency information of the modulated radio frequency can be obtained in real time. By introducing a small phase shift θ (assumed to be positive), the phase difference between the radio frequency signals received by the antenna can be deduced by reading the amplitudes of two sets of pulses with positive and negative offsets. By introducing the phase shift θ, the unambiguous testing range of the phase is extended from [-π / 2, π / 2] to [-π+θ, π-θ]. The angle of arrival α of the radio frequency signal can be measured according to the following relationship: , In one embodiment, optionally, the phase difference between the first radio frequency signal and the second radio frequency signal is calculated using the following formula: =arcsin[(I + -I - ) / (Vref)], in, I represents the phase difference. + I represents the pulse amplitude after introducing a positive phase shift. - Vref represents the pulse amplitude after introducing a negative phase shift, and Vref represents the calibration normalization factor. Vref is the peak pulse amplitude obtained by measuring under a zero-degree angle of arrival condition.

[0059] In one embodiment, optionally, the angle of arrival is calculated based on the relationship between the phase difference and the antenna element spacing, satisfying the following condition: =2πd sinα / λ, Where λ represents the wavelength of the radio frequency signal. Let α represent the phase difference, α represent the angle of arrival, and d represent the antenna element spacing.

[0060] In one embodiment, optionally, the spacing between the first antenna element and the second antenna element is half the wavelength of the first or second radio frequency signal.

[0061] In one embodiment, optionally, the silicon nitride microring includes a high-Q silicon nitride integrated microring, the output frequency of the tunable laser matches the resonant mode of the silicon nitride microring, and the intracavity dispersion and nonlinear effects of the silicon nitride microring are balanced.

[0062] In one embodiment, optionally, the preset phase difference ranges from 0 < θ < π, which is used to extend the phase ambiguity test range from [-π / 2, π / 2] to [-π+θ, π-θ], eliminating angular ambiguity on both sides of the normal.

[0063] In one embodiment, optionally, the dispersion of the dispersive fiber satisfies the Talbot condition, such that the frequency of the radio frequency signal is linearly related to the time interval between adjacent peaks of the electrical pulse train.

[0064] In one embodiment, optionally, the optical frequency comb generation module further includes a programmable optical filter for spectral shaping of the coherent optical frequency comb and outputting light pulses with a preset repetition period.

[0065] In one embodiment, optionally, the oscilloscope includes a real-time oscilloscope for observing the time interval between adjacent peaks of the electrical pulse train to obtain the frequency of the radio frequency signal, and for inferring the phase difference between the first radio frequency signal and the second radio frequency signal by the difference in the amplitude of adjacent peaks.

[0066] In addition, this application provides a computer-readable storage medium storing computer-executable instructions for performing the following steps: amplifying a narrow-linewidth laser generated by a tunable laser through an erbium-doped fiber amplifier, and coupling it as pump light to a silicon nitride microring to excite the Kerr nonlinear effect to generate a coherent optical frequency comb; receiving a first radio frequency (RF) signal and a second RF signal through a first antenna element and a second antenna element respectively, wherein the interval between the first antenna element and the second antenna element is half the wavelength of the RF signal; inputting the first RF signal and the second RF signal into the first and second sub-modulators of a dual parallel Mach-Zehnder modulator respectively, modulating the coherent optical frequency comb with a minimum bias point, merging the first and second modulated lights through a third sub-modulator, and introducing a preset phase difference to obtain a target optical pulse signal; inputting the target optical pulse signal into a dispersive fiber, realizing frequency-time mapping based on the Talbot effect, and converting it into an electrical pulse train through a photodetector; observing the adjacent peak time interval and pulse amplitude information of the electrical pulse train through an oscilloscope to obtain characteristic parameters of the RF signal, wherein the characteristic parameters include at least frequency and angle of arrival information.

[0067] It should be understood that although the terms "first," "second," etc., may be used to describe radio frequency signals in the embodiments of this application, these radio frequency signals should not be limited to these terms. These terms are only used to distinguish radio frequency signals from one another. For example, without departing from the scope of the embodiments of this application, a first radio frequency signal may also be referred to as a second radio frequency signal, and similarly, a second radio frequency signal may also be referred to as a first radio frequency signal.

[0068] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0069] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A microwave photonic system for measuring frequency and angle of arrival at the nanosecond level, characterized in that, The system includes: An optical frequency comb generation module includes a tunable laser, an erbium-doped fiber amplifier, and a silicon nitride microring. The narrow linewidth laser generated by the tunable laser is amplified by the erbium-doped fiber amplifier and then used as pump light coupled to the silicon nitride microring to excite the Kerr nonlinear effect and generate a coherent optical frequency comb. The antenna receiving module includes a first antenna array element and a second antenna array element, used to receive a first radio frequency signal and a second radio frequency signal; The electro-optic modulation module is a dual parallel Mach-Zehnder modulator, including a first sub-modulator, a second sub-modulator and a third sub-modulator. The first radio frequency signal and the second radio frequency signal are respectively input to the first sub-modulator and the second sub-modulator to generate the first modulated light and the second modulated light with the minimum bias point. The third sub-modulator is used to merge the first modulated light and the second modulated light and introduce a preset phase difference to obtain the target light pulse signal. The frequency-time mapping and detection module includes a dispersive optical fiber, a photodetector, and an oscilloscope. The target optical pulse signal is frequency-time mapped via the dispersive optical fiber. The photodetector converts the mapped optical signal into an electrical pulse train. The oscilloscope is used to observe the time interval between adjacent peaks and the pulse amplitude information of the electrical pulse train to obtain the characteristic parameters of the radio frequency signal. The characteristic parameters include at least frequency and angle of arrival information.

2. The microwave photonic system according to claim 1, characterized in that, The spacing between the first antenna element and the second antenna element is half the wavelength of the first or second radio frequency signal.

3. The microwave photonic system according to claim 1, characterized in that, The silicon nitride microring includes a high-Q silicon nitride integrated microring, the output frequency of the tunable laser matches the resonant mode of the silicon nitride microring, and the intracavity dispersion and nonlinear effects of the silicon nitride microring are balanced.

4. The microwave photonic system according to claim 1, characterized in that, The preset phase difference has a value range of 0 < θ < π, which is used to extend the phase ambiguity test range from [-π / 2, π / 2] to [-π+θ, π-θ], eliminating the angular ambiguity on both sides of the normal.

5. The microwave photonic system according to claim 1, characterized in that, The dispersion of the dispersive fiber satisfies the Talbot condition, so that the frequency of the radio frequency signal and the time interval between adjacent peaks of the electrical pulse train are linearly related.

6. The microwave photonic system according to claim 1, characterized in that, The optical frequency comb generation module also includes a programmable optical filter for spectral shaping of the coherent optical frequency comb and outputting light pulses with a preset repetition period.

7. The microwave photonic system according to claim 1, characterized in that, The oscilloscope includes a real-time oscilloscope, used to observe the time interval between adjacent peaks of the electrical pulse train to obtain the frequency of the radio frequency signal, and to infer the phase difference between the first radio frequency signal and the second radio frequency signal by using the pulse amplitude information of adjacent peaks.

8. A method for measuring frequency and angle of arrival at the nanosecond level, characterized in that, A microwave photonic system for frequency and angle-of-arrival nanosecond-level measurements according to any one of claims 1 to 7, the method comprising: Narrow-linewidth laser light generated by a tunable laser is amplified by an erbium-doped fiber amplifier and used as pump light to couple to a silicon nitride microring, thereby exciting the Kerr nonlinear effect to generate a coherent optical frequency comb. The first antenna element and the second antenna element receive the first radio frequency signal and the second radio frequency signal respectively. The interval between the first antenna element and the second antenna element is half the wavelength of the radio frequency signal. The first radio frequency signal and the second radio frequency signal are respectively input into the first sub-modulator and the second sub-modulator of the dual parallel Mach-Zehnder modulator, and the coherent optical frequency comb is modulated with the minimum bias point. The first modulated light and the second modulated light generated by the third sub-modulator are combined and a preset phase difference is introduced to obtain the target light pulse signal. The target optical pulse signal is input into a dispersive fiber, and frequency-time mapping is achieved based on the Talbot effect. It is then converted into an electrical pulse train by a photodetector. The characteristic parameters of the radio frequency signal are obtained by observing the adjacent peak time interval and pulse amplitude information of the electrical pulse train using an oscilloscope, wherein the characteristic parameters include at least frequency and angle of arrival information.

9. The method according to claim 8, characterized in that, The phase difference between the first radio frequency signal and the second radio frequency signal is calculated using the following formula: φ=arcsin[(I + -I - ) / (2βI0)] Where φ represents the phase difference, I + I represents the pulse amplitude after introducing a positive phase shift. - I0 represents the pulse amplitude after introducing a negative phase shift, β represents the modulation depth of the RF signal on the modulator, and I0 represents the reference pulse amplitude without phase shift.

10. The method according to claim 8, characterized in that, The angle of arrival is calculated based on the relationship between the phase difference and the antenna element spacing, satisfying the following condition: φ=2πd sine / min Where λ represents the wavelength of the radio frequency signal, φ represents the phase difference, α represents the angle of arrival, and d represents the spacing between the antenna elements.

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