Microwave photonics based nonlinear swept-frequency velocimeter and rangefinder

Abstract

The application discloses a nonlinear sweep frequency velocity and distance measuring device based on microwave photon technology, and is characterized by comprising a single-frequency laser, a nonlinear microwave source, a microwave-optical modulation module, a coupler, a circulator, an optical probe, a demultiplexer, a first photoelectric detector, a second photoelectric detector, an F-P etalon, a third photoelectric detector, a synchronous acquisition card and a demodulation module. The application solves the problems of large measurement error and insufficient measurement rate when a traditional sweep frequency interference system measures a dynamic target, and makes it possible to measure a high-speed moving target by using the sweep frequency interference.

Description

Technical Field

[0001] This invention belongs to the field of microwave photonics measurement technology, and particularly relates to a nonlinear sweep frequency velocity and distance measurement device and method based on microwave photonics technology. Background Technology

[0002] In the field of laser ranging, swept-frequency interferometric ranging is advantageous due to its large ranging range (without 2...). π Its advantages, such as the limitation of range due to phase ambiguity and high ranging accuracy (which can be improved by increasing the sweep bandwidth), have always dominated the field of ranging in military, industrial and scientific research applications.

[0003] When a swept-frequency interferometer measures a moving target, in addition to the Doppler effect caused by the target's motion (which introduces measurement errors), the sweep frequency nonlinearity of the laser source also severely degrades the measurement accuracy. As the core of the swept-frequency interferometric system, the swept-frequency light source must ensure strictly linear sweep frequency to theoretically guarantee high-precision ranging output. However, real-world light sources always exhibit various nonlinear effects, and the frequency of their output swept light often suffers from severe nonlinearity. Therefore, before performing frequency sweep interferometric ranging, various precise and complex software and hardware methods must be employed to correct the frequency sweep nonlinearity of the light source (e.g., patent CN201620548960.6 uses closed-loop feedback optical phase-locked loop to correct nonlinearity, patent 202110337099.4 uses expanded phase frequency sampling to correct nonlinearity, patent CN200410092447.2 uses piecewise voltage-controlled oscillation to correct nonlinearity, patent CN202110154331.0 uses similar triangular interpolation sampling to correct nonlinearity, and patent CN201910710774.6 uses time-domain measurement result compensation to correct nonlinearity). To achieve linear frequency sweep output, the above methods not only increase the difficulty of system implementation and measurement costs but also reduce system reliability. On the other hand, since traditional frequency sweep interferometric measurement can only obtain one distance value within one frequency sweep cycle, its dynamic range is smaller than... f sweep / 2( f sweep This refers to the laser's sweep frequency (typically in the kHz range); frequencies exceeding this range cannot be measured. f sweep / 2 dynamic target. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a nonlinear sweep frequency velocity and distance measurement device and method based on microwave photonics technology. This solves the problems of large measurement error and insufficient measurement rate when the traditional sweep frequency interferometric system measures dynamic targets, making it possible to measure high-speed moving targets by sweep frequency interferometric measurement.

[0005] The objective of this invention is achieved through the following technical solution: a nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, comprising: a single-frequency laser, a nonlinear microwave source, a microwave-optical modulation module, a coupler, a circulator, an optical probe, a demultiplexer, a first photodetector, a second photodetector, an FP etalon, a third photodetector, a synchronous acquisition card, and a demodulation module; wherein, the single-frequency laser generates an optical carrier, which enters the microwave-optical modulation module along an optical fiber; the nonlinear microwave source generates a nonlinear sweep frequency microwave signal that is transmitted to the microwave-optical modulation module, and the microwave-optical modulation module generates nonlinear sweep frequency light with upper and lower sidebands; The upper and lower sideband nonlinear sweep beams enter the coupler and are divided into a first upper and lower sideband nonlinear sweep beam and a second upper and lower sideband nonlinear sweep beam. The first upper and lower sideband nonlinear sweep beams pass through the circulator and reach the optical probe. A portion of the first upper and lower sideband nonlinear sweep beams is reflected by the optical probe to form a reference beam, while the other portion exits at the probe end face. The exited beam is reflected by the moving target and re-enters the optical probe to form a measurement beam. The reference beam and the measurement beam pass through the circulator again and, after routing, reach the demultiplexer. The demultiplexer separates the reference beam according to wavelength to form an upper sideband sweep reference beam and a lower sideband sweep reference beam. The multiplexer separates the measurement light by wavelength to form an upper sideband swept measurement light and a lower sideband swept measurement light. The upper sideband swept reference light and the upper sideband swept measurement light are transmitted to the first photodetector, and the lower sideband swept reference light and the lower sideband swept measurement light are transmitted to the second photodetector. The upper sideband swept reference light and the upper sideband swept measurement light are coherently superimposed to generate an upper sideband ranging signal. This upper sideband ranging signal is then photoelectrically converted by the first photodetector to obtain an upper sideband ranging electrical signal, which enters the synchronous acquisition card. The lower sideband swept reference light and the lower sideband swept measurement light are coherently superimposed to generate a lower sideband ranging signal. This lower sideband ranging signal is then photoelectrically converted by the second photodetector... The lower sideband ranging electrical signal is input into the synchronous acquisition card; the second upper and lower sideband nonlinear sweep frequency light is converted into a nonlinear sweep frequency interference optical signal by the FP standard, and the nonlinear sweep frequency interference optical signal is transmitted to the third photodetector; the nonlinear sweep frequency interference optical signal is converted into a nonlinear sweep frequency interference electrical signal by the third photodetector and input into the synchronous acquisition card; the synchronous acquisition card samples the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear sweep frequency interference electrical signal and transmits them to the demodulation module; the demodulation module obtains the real-time distance and velocity of the moving target based on the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear sweep frequency interference electrical signal.

[0006] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the upper and lower sideband nonlinear sweep frequency light is obtained by the following formula:

[0007] ;

[0008] in, The amplitude of the sweep frequency optical wave in the upper and lower sidebands. For the output light amplitude of a single-frequency laser, The output light frequency of a single-frequency laser. Let be the nonlinear sweep frequency at time t. T The frequency sweep period of the microwave source. t For a moment, n It can be 0 or 1.

[0009] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the upper sideband ranging signal is obtained through the following formula:

[0010] ;

[0011] in, The upper band ranging signal, This represents the real-time phase of the upper sideband ranging signal. l ( t )for t The real-time distance of a moving target. c At the speed of light, The frequency sweep period of the microwave source. For a moment, The output light frequency of a single-frequency laser. Let be the nonlinear sweep frequency at time t.

[0012] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the lower sideband ranging signal is obtained through the following formula:

[0013] ;

[0014] in, The signal is a bottom-band ranging signal. This represents the real-time phase of the lower sideband ranging signal. l ( t )for t The real-time distance of a moving target at all times. c At the speed of light, The frequency sweep period of the microwave source. For a moment, The output light frequency of a single-frequency laser. Let be the nonlinear sweep frequency at time t.

[0015] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the nonlinear sweep frequency interference optical signal is obtained through the following formula:

[0016] ;

[0017] in, It is a nonlinear frequency-sweeping interference optical signal. The real-time phase of the nonlinear swept-frequency interference optical signal. For FP gauge length, This is the initial sweep frequency of the microwave source. For a moment.

[0018] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the real-time distance to the moving target is obtained using the following formula:

[0019] ;

[0020] in, The real-time distance to the moving target. This is the phase increment of the upper sideband ranging signal. This represents the phase increment of the lower sideband ranging signal. The phase increment of the nonlinear swept-frequency interference optical signal. This is the initial sweep frequency of the microwave source. For a moment, The frequency sweep period of the microwave source. This refers to the output optical frequency of a single-frequency laser.

[0021] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the phase increment of the upper sideband ranging signal... Phase increment of the lower sideband ranging signal The following relationship exists:

[0022] ;

[0023] Where, Δ l ( t () represents the dynamic distance change within a single frequency sweep cycle. Let be the nonlinear sweep frequency at time t.

[0024] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the phase increment of the nonlinear sweep frequency interference optical signal... It can be obtained through the following formula:

[0025] ;

[0026] This represents the phase increment of the nonlinear swept-frequency interference optical signal.

[0027] In the aforementioned nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, the upper and lower sideband nonlinear sweep frequency light is a nonlinear sweep frequency light with the optical carrier frequency as the center and completely mirror-symmetrical from left to right.

[0028] A nonlinear sweep frequency velocity and ranging method based on microwave photonics technology includes: a single-frequency laser generating an optical carrier, which enters a microwave-optical modulation module along an optical fiber; a nonlinear microwave source generating a nonlinear sweep frequency microwave signal, which is transmitted to the microwave-optical modulation module, which generates upper and lower sideband nonlinear sweep frequency light; the upper and lower sideband nonlinear sweep frequency light entering a coupler and splitting into first upper and lower sideband nonlinear sweep frequency light and second upper and lower sideband nonlinear sweep frequency light; the first upper and lower sideband nonlinear sweep frequency light passing through a circulator and reaching an optical probe; a portion of the first upper and lower sideband... The nonlinear swept light is reflected by the optical probe to form a reference light. Another portion of the first upper and lower sideband nonlinear swept light exits at the probe end face. This exiting light is reflected by the moving target and re-enters the optical probe to form the measurement light. The reference light and measurement light pass through the circulator again and, after routing, reach the demultiplexer. The demultiplexer separates the reference light by wavelength to form an upper sideband swept reference light and a lower sideband swept reference light. Similarly, the demultiplexer separates the measurement light by wavelength to form an upper sideband swept measurement light and a lower sideband swept measurement light. The upper sideband swept reference light and upper sideband swept measurement light are then transmitted to… The first photodetector transmits the lower sideband sweep frequency reference light and the lower sideband sweep frequency measurement light to the second photodetector; the upper sideband sweep frequency reference light and the upper sideband sweep frequency measurement light are coherently superimposed to generate an upper sideband ranging signal, which is then photoelectrically converted by the first photodetector to obtain an upper sideband ranging electrical signal that enters the synchronous acquisition card; the lower sideband sweep frequency reference light and the lower sideband sweep frequency measurement light are coherently superimposed to generate a lower sideband ranging signal, which is then photoelectrically converted by the second photodetector to obtain a lower sideband ranging electrical signal that enters the synchronous acquisition card; the second upper and lower sideband... The nonlinear swept frequency light is passed through the FP standard to obtain a nonlinear swept frequency interference light signal, which is then transmitted to the third photodetector. The nonlinear swept frequency interference light signal is converted by the third photodetector to obtain a nonlinear swept frequency interference electrical signal, which enters the synchronous acquisition card. The synchronous acquisition card samples the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear swept frequency interference electrical signal and transmits them to the demodulation module. The demodulation module obtains the real-time distance and velocity of the moving target based on the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear swept frequency interference electrical signal.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) In order to solve the problem that the sweep frequency interferometric ranging system is heavily dependent on the linear sweep frequency light source, the present invention proposes a nonlinear sweep frequency microwave photon velocity and ranging method. This method can realize sweep frequency interferometric ranging by using a nonlinear sweep frequency light source, which reduces the difficulty of system implementation, reduces hardware and software costs, and improves system reliability.

[0031] (2) While eliminating Doppler error, the present invention can also provide the distance value corresponding to all sampling times within a sweep cycle, thereby achieving an order-of-magnitude increase in the system measurement rate.

[0032] (3) This invention solves the problems of large measurement error and insufficient measurement rate when the traditional sweep frequency interferometric system measures dynamic targets, making it possible to measure high-speed moving targets by sweep frequency interferometric measurement. Attached Figure Description

[0033] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0034] Figure 1 This is a schematic diagram of the structure of the nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of a nonlinear double-sideband swept-frequency optical system provided in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the phase increment of the double-sideband measurement signal provided in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of a distance measurement example provided in an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of a speed measurement example provided in an embodiment of the present invention. Detailed Implementation

[0039] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] Figure 1 This is a schematic diagram of the structure of the nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology provided in an embodiment of the present invention. Figure 1 As shown, the device includes a single-frequency laser, a nonlinear microwave source, a microwave-optical modulation module, a coupler, a circulator, an optical probe, a demultiplexer, a first photodetector, a second photodetector, an FP etalon, a third photodetector, a synchronous acquisition card, and a demodulation module; wherein,

[0041] The single-frequency laser generates an optical carrier, which enters the microwave-optical modulation module along an optical fiber; the nonlinear microwave source generates a nonlinear swept-frequency microwave signal, which is transmitted to the microwave-optical modulation module. Specifically, the single-frequency laser generates a narrowband optical carrier, which is modulated by the microwave-optical modulation module, and the nonlinear swept-frequency microwave signal is modulated onto the optical carrier to generate upper and lower sideband nonlinear swept-frequency optical outputs that are perfectly mirror-symmetrical with the carrier frequency as the center.

[0042] The microwave-optical modulation module generates upper and lower sideband nonlinear sweep light. This upper and lower sideband nonlinear sweep light enters the coupler and splits into a first upper and lower sideband nonlinear sweep light and a second upper and lower sideband nonlinear sweep light. The first upper and lower sideband nonlinear sweep light passes through the circulator and reaches the optical probe. A portion of the first upper and lower sideband nonlinear sweep light is reflected by the optical probe to form a reference light, while another portion exits at the probe end face. The exited light is reflected by the moving target and re-enters the optical probe to form a measurement light. The reference light and measurement light pass through the circulator again and, after routing, reach the demultiplexer. The demultiplexer separates the reference light by wavelength to form an upper sideband sweep reference light and a lower sideband sweep reference light. The demultiplexer also separates the measurement light by wavelength to form an upper sideband sweep measurement light and a lower sideband sweep measurement light. The upper sideband sweep reference light and the upper sideband sweep measurement light are transmitted to the first photodetector, and the lower sideband sweep reference light and the lower sideband sweep measurement light are transmitted to the second photodetector. A sweeping reference light and a sweeping measurement light on the upper sideband are coherently superimposed to generate an upper sideband ranging signal. This upper sideband ranging signal is then photoelectrically converted by a first photodetector to obtain an upper sideband ranging electrical signal, which enters the synchronous acquisition card. Similarly, a sweeping reference light on the lower sideband and a sweeping measurement light on the lower sideband are coherently superimposed to generate a lower sideband ranging signal. This lower sideband ranging signal is then photoelectrically converted by a second photodetector to obtain a lower sideband ranging electrical signal, which enters the synchronous acquisition card. Second upper and lower sideband nonlinear sweeping light passes through an FP etalon to obtain a nonlinear sweeping interference light signal, which is then transmitted to the third photodetector. This nonlinear sweeping interference light signal is converted by the third photodetector to obtain a nonlinear sweeping interference electrical signal, which enters the synchronous acquisition card. The synchronous acquisition card samples the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear sweeping interference electrical signal and transmits them to the demodulation module. The demodulation module obtains the real-time distance and velocity of the moving target based on these signals.

[0043] After a nonlinear microwave source modulates a single-frequency optical carrier, the modulator generates double-sideband nonlinear swept light, i.e., upper and lower sideband nonlinear swept light, as follows:

[0044]

[0045] in, Eout ( t () represents the amplitude of the upper and lower sideband swept frequency optical wave. E 0 represents the output light amplitude of a single-frequency laser. f c The output light frequency of a single-frequency laser. e ( t Let be the nonlinear sweep frequency at time t. T The frequency sweep period of the microwave source. t For time variables, n It is either 0 or 1, and n is the exponent. n =0 corresponds to the nonlinear sweep frequency of the upper band. n =1 corresponds to the nonlinear sweep frequency of the lower band.

[0046] E out ( t The velocity and distance information of the target object is transmitted and carried out by the measurement system. Finally, photoelectric conversion is completed by the first photodetector and the second photodetector to obtain two nonlinear measurement signals, namely the upper sideband ranging signal and the lower sideband ranging signal.

[0047] ;

[0048] ;

[0049] in, The upper band ranging signal, This represents the real-time phase of the upper sideband ranging signal. The signal is a bottom-band ranging signal. This represents the real-time phase of the lower sideband ranging signal. l ( t Let t be the real-time distance of the moving target at time t, and c be the speed of light. The frequency sweep period of the microwave source. For a moment, The output light frequency of a single-frequency laser. Let be the nonlinear sweep frequency at time t.

[0050] right , Phase unwrapping yields the phase increment Δ φ 1( t ), Δ φ 2( t The two have the following relationship:

[0051]

[0052] Where Δ l ( t ), e0 represents the dynamic distance change within a single sweep cycle and the initial sweep frequency of the microwave source. Furthermore, the signal obtained by detector 3 can be expressed as:

[0053]

[0054] in, a FP The length of the FP marker is determined by the signal. s 3( t Incremental phase Δ φ 3( t ) can be obtained

[0055]

[0056] This represents the phase increment of the nonlinear swept-frequency interference optical signal.

[0057] Δ e ( t The change in optical frequency within a single sweep cycle is denoted by (). Furthermore, the continuous change distance and instantaneous velocity within one sweep cycle can be obtained from the above formula:

[0058]

[0059] Therefore, three measurement signals are obtained. s 1. s 2 phase increment Δ φ 1( t ), Δ φ 2( t After that, the single sweep frequency cycle can be obtained using the above formula. T velocity value at any time within υ ( t ), and dynamic distance values l ( t ).

[0060] This embodiment also provides a nonlinear frequency sweep velocity and distance measurement method based on microwave photonics technology, which includes the following steps:

[0061] A single-frequency laser generates an optical carrier, which enters the microwave-optical modulation module along an optical fiber.

[0062] A nonlinear microwave source generates a nonlinear swept-frequency microwave signal, which is transmitted to a microwave-optical modulation module. The microwave-optical modulation module generates upper and lower sideband nonlinear swept-frequency beams. These beams enter a coupler and split into first and second upper and lower sideband nonlinear swept-frequency beams. The first upper and lower sideband nonlinear swept-frequency beam passes through a circulator and reaches an optical probe. A portion of the first upper and lower sideband nonlinear swept-frequency beam is reflected by the optical probe to form a reference beam, while the other portion exits at the probe end face. The exited beam is reflected by a moving target and re-enters the optical probe to form a measurement beam. The reference beam and measurement beam pass through the circulator again and, after routing, reach a demultiplexer. The demultiplexer separates the reference beam by wavelength to form an upper sideband swept-frequency reference beam and a lower sideband swept-frequency reference beam. The demultiplexer also separates the measurement beam by wavelength to form an upper sideband swept-frequency measurement beam and a lower sideband swept-frequency measurement beam. The upper sideband swept-frequency reference beam and the upper sideband swept-frequency measurement beam are transmitted to a first photodetector, and the lower sideband swept-frequency reference beam and the lower sideband swept-frequency measurement beam are transmitted to a first photodetector. The signal is fed to the second photodetector; the upper sideband sweep frequency reference light and the upper sideband sweep frequency measurement light are coherently superimposed to generate the upper sideband ranging signal. The upper sideband ranging signal is then photoelectrically converted by the first photodetector to obtain the upper sideband ranging electrical signal, which enters the synchronous acquisition card; the lower sideband sweep frequency reference light and the lower sideband sweep frequency measurement light are coherently superimposed to generate the lower sideband ranging signal. The lower sideband ranging signal is then photoelectrically converted by the second photodetector to obtain the lower sideband ranging electrical signal, which enters the synchronous acquisition card; the second upper and lower sideband nonlinear sweep frequency light is passed through the FP etalon to obtain the nonlinear sweep frequency interference light signal, which is then transmitted to the third photodetector; the nonlinear sweep frequency interference light signal is converted by the third photodetector to obtain the nonlinear sweep frequency interference electrical signal, which enters the synchronous acquisition card; the synchronous acquisition card samples the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear sweep frequency interference electrical signal and transmits them to the demodulation module; the demodulation module obtains the real-time distance and velocity of the moving target based on the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear sweep frequency interference electrical signal.

[0063] The specific implementation steps of this method are as follows:

[0064] 1) Install the sensor probe along the direction of motion of the target to be measured;

[0065] 2) Obtain the interferometric measurement signal;

[0066] 3) Perform distance and velocity calculations;

[0067] 3)-A. Obtain the three-channel data obtained from the measurement;

[0068] 3)-B. Separate the obtained data by channel, which are the measurement signals 1 obtained by the first detector: s 1[ n ] Measured signal 2 obtained from the second detector: s 2[n Reference signal 2 obtained from the third detector: s 3[ n ];

[0069] 3)-C. Perform Hilbert transform on the above signals respectively, and obtain the incremental phase Δ corresponding to each signal according to equation (1). φ 1[ n ]、Δ φ 2[ n ]、Δ φ 3[ n ];

[0070] (1)

[0071] in, For signal The Hilbert transform, where Im and Re denote taking the real and imaginary parts, respectively;

[0072] 3)-D. Calculate the instantaneous velocity within one sweep cycle according to formula (2). υ [ n ]

[0073] (2)

[0074] Diff Represents discrete differential, t [ n [ ] represents the sampling time within one sweep cycle;

[0075] 3)-E. Further, according to Δ φ 3[ n Calculate the sweep frequency nonlinearity within a single sweep frequency cycle.

[0076] (3)

[0077] 3)-F. Δ e [ n ]、Δ φ 1[ n ]、Δ φ 2[ n Substituting into equation (4), we can obtain the instantaneous distance within one sweep cycle. l [ n ]:

[0078] (4)

[0079] The system features a single-frequency laser with an output wavelength of 1550 nm, a microwave source with a starting sweep frequency of 20 GHz, a bandwidth of 10 GHz, a nonlinearity of 1 GHz (10% nonlinearity), and a sweep frequency of... fsweep At 500 Hz, for a vibrating target with an amplitude of 200 μm and a frequency of 400 Hz at a distance of 20 m, the nonlinear double-sideband swept-frequency optical signal, such as Figure 2 As shown, the phase increment of the double-sideband measurement signal is as follows: Figure 3 As shown, this embodiment achieves a measurement rate of up to 10 MHz, an accuracy better than 1 μm, and a velocity measurement accuracy better than 0.01 m / s. The measurement results are as follows: Figure 4 , Figure 5 As shown.

[0080] This example implements nonlinear swept-frequency interferometric velocity and distance measurement, while improving the system's dynamic range to 5 MHz (the dynamic range of a traditional swept-frequency interferometric system is...). f sweep / 2=250 Hz), which improves the system's dynamic range by 4 orders of magnitude.

[0081] The microwave photonic sweep frequency interferometric ranging method proposed in this embodiment only requires a single-frequency laser, a nonlinear sweep frequency microwave source, and a double-sideband modulator to obtain a dual-path fully mirrored nonlinear sweep frequency light source (the above light source is almost impossible to achieve in the non-microwave photonics field), and uses this mirrored nonlinear sweep frequency light source to realize distance measurement based on nonlinear sweep frequency interferometry.

[0082] From the perspective of application effect, this embodiment can not only eliminate Doppler error, but also, compared with existing solutions (within one frequency sweep cycle) T (While traditional sweep frequency interferometry systems can only measure one distance and one velocity value, this embodiment can provide velocity and distance values ​​corresponding to all sampling moments within a single sweep frequency cycle, thereby increasing the system's measurement rate by orders of magnitude. This embodiment solves the problems of large measurement errors and insufficient measurement rates in traditional sweep frequency interferometry systems when measuring dynamic targets, making it possible to measure high-speed moving targets using sweep frequency interferometry.)

[0083] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology, characterized in that... include: The system includes a single-frequency laser, a nonlinear microwave source, a microwave-optical modulation module, a coupler, a circulator, an optical probe, a demultiplexer, a first photodetector, a second photodetector, an FP etalon, a third photodetector, a synchronous acquisition card, and a demodulation module; among which, The single-frequency laser generates an optical carrier, which enters the microwave-optical modulation module along the optical fiber. The nonlinear microwave source generates a nonlinear swept-frequency microwave signal, which is transmitted to the microwave-optical modulation module. The microwave-optical modulation module generates upper and lower sideband nonlinear swept-frequency light. The upper and lower sideband nonlinear swept-frequency light enters the coupler and splits into a first upper and lower sideband nonlinear swept-frequency light and a second upper and lower sideband nonlinear swept-frequency light. The first upper and lower sideband nonlinear swept-frequency light passes through the circulator and reaches the optical probe. A portion of the first upper and lower sideband nonlinear swept-frequency light is reflected by the optical probe to form a reference light, and another portion of the first upper and lower sideband nonlinear swept-frequency light exits at the end face of the optical probe. The exited light is reflected by the moving target and re-enters the optical probe to form a measurement light. The reference light and the measurement light pass through the circulator again and, after routing, reach the demultiplexer. The demultiplexer separates the reference light according to wavelength to form an upper sideband swept-frequency reference light and a lower sideband swept-frequency reference light. The demultiplexer separates the measurement light according to wavelength to form an upper sideband swept-frequency measurement light and a lower sideband swept-frequency measurement light. The upper sideband swept-frequency reference light and the upper sideband swept-frequency measurement light are transmitted to the first photodetector, and the lower sideband swept-frequency reference light and the lower sideband swept-frequency measurement light are transmitted to the first photodetector. The upper sideband sweep reference light and the upper sideband sweep measurement light are coherently superimposed to generate an upper sideband ranging signal. The upper sideband ranging signal is then photoelectrically converted by the first photodetector to obtain an upper sideband ranging electrical signal, which enters the synchronous acquisition card. The lower sideband sweep reference light and the lower sideband sweep measurement light are coherently superimposed to generate a lower sideband ranging signal. The lower sideband ranging signal is then photoelectrically converted by the second photodetector to obtain a lower sideband ranging electrical signal, which enters the synchronous acquisition card. The second upper and lower sideband nonlinear sweep light is converted by the FP etalon to obtain a nonlinear sweep interference light signal, which is then transmitted to the third photodetector. The nonlinear sweep interference light signal is converted by the third photodetector to obtain a nonlinear sweep interference electrical signal, which enters the synchronous acquisition card. The synchronous acquisition card acquires the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear sweep interference electrical signal and transmits them to the demodulation module. The demodulation module obtains the real-time distance and velocity of the moving target based on the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear sweep interference electrical signal.

2. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 1, characterized in that: The nonlinear sweep beam with upper and lower sidebands is obtained by the following formula: Among them, E out (t) represents the amplitude of the sweeping light in the upper and lower sidebands, E0 represents the amplitude of the output light from the single-frequency laser, and f c Let e(t) be the output light frequency of the single-frequency laser, e(t) be the nonlinear sweep frequency at time t, T be the sweep period of the nonlinear microwave source, t be the time, and n be 0 or 1.

3. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 1, characterized in that: The upper band ranging signal is obtained by the following formula: Where s1(t) is the upper sideband ranging signal, Let f be the real-time phase of the upper sideband ranging signal, l(t) be the real-time distance of the moving target at time t, c be the speed of light, T be the frequency sweep period of the nonlinear microwave source, t be the time, and f be the distance between the moving target and the moving target. c Let e(t) be the output light frequency of the single-frequency laser, and let e(t) be the nonlinear sweep frequency at time t.

4. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 1, characterized in that: The lower sideband ranging signal is obtained using the following formula: Where s2(t) is the lower sideband ranging signal, Let f be the real-time phase of the lower sideband ranging signal, l(t) be the real-time distance of the moving target at time t, c be the speed of light, T be the frequency sweep period of the nonlinear microwave source, t be the time, and f be the distance to the moving target at time t. c Let e(t) be the output light frequency of the single-frequency laser, and let e(t) be the nonlinear sweep frequency at time t.

5. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 1, characterized in that: The nonlinear swept frequency interference optical signal is obtained by the following formula: Wherein, s3(t) is the nonlinear swept frequency interference optical signal. For the real-time phase of the nonlinear swept-frequency interference optical signal, a FP Let FP be the length of the etalon, e0 be the initial sweep frequency of the nonlinear microwave source, t be the time, c be the speed of light, and e(t) be the nonlinear sweep frequency at time t.

6. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 1, characterized in that: The real-time distance to a moving target is obtained using the following formula: Where l(t) is the real-time distance of the moving target. This is the phase increment of the upper sideband ranging signal. Let f be the phase increment of the lower sideband ranging signal, Δe(t) be the nonlinear sweep frequency increment at time t, e0 be the initial sweep frequency of the nonlinear microwave source, t be the time, T be the sweep period of the nonlinear microwave source, and f be the phase increment of the lower sideband ranging signal. c is the output light frequency of the single-frequency laser, and c is the speed of light.

7. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 6, characterized in that: Phase increment of the upper band ranging signal Phase increment of the lower sideband ranging signal The following relationship exists: Where Δl(t) is the dynamic distance change within a single sweep cycle, and e(t) is the nonlinear sweep frequency at time t.

8. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 6, characterized in that: The nonlinear sweep frequency increment Δe(t) at time t is obtained by the following formula: Among them, a FP Let FP be the length of the etalon, and c be the speed of light. This represents the phase increment of the nonlinear swept-frequency interference optical signal.

9. The nonlinear sweep frequency velocity and distance measuring device based on microwave photonics technology according to claim 6, characterized in that: The upper and lower sideband nonlinear sweeping light is a nonlinear sweeping light with the optical carrier frequency as the center and completely mirror-symmetrical left and right sides.

10. A nonlinear sweep frequency velocity and distance measurement method based on microwave photonics technology, characterized in that... include: A single-frequency laser generates an optical carrier, which enters the microwave-optical modulation module along an optical fiber. A nonlinear microwave source generates a nonlinear swept-frequency microwave signal, which is transmitted to a microwave-optical modulation module. The microwave-optical modulation module generates upper and lower sideband nonlinear swept-frequency light. The upper and lower sideband nonlinear swept-frequency light enters the coupler and is divided into a first upper and lower sideband nonlinear swept-frequency light and a second upper and lower sideband nonlinear swept-frequency light. The first upper and lower sideband nonlinear swept-frequency light passes through a circulator and reaches the optical probe. A portion of the first upper and lower sideband nonlinear sweep light is reflected by the optical probe to form reference light, while another portion of the first upper and lower sideband nonlinear sweep light is emitted from the end face of the optical probe. The emitted light is reflected by the moving target and re-enters the optical probe to form measurement light. The reference light and the measurement light pass through the circulator again and reach the demultiplexer after routing. The demultiplexer splits the reference light according to wavelength to form an upper sideband swept reference light and a lower sideband swept reference light. The demultiplexer splits the measurement light according to wavelength to form an upper sideband swept measurement light and a lower sideband swept measurement light. The upper sideband swept reference light and the upper sideband swept measurement light are transmitted to the first photodetector, and the lower sideband swept reference light and the lower sideband swept measurement light are transmitted to the second photodetector. The upper sideband sweep reference light and the upper sideband sweep measurement light are coherently superimposed to generate an upper sideband ranging signal. The upper sideband ranging signal is then photoelectrically converted by the first photodetector to obtain an upper sideband ranging electrical signal, which enters the synchronous acquisition card. The lower sideband sweep reference light and the lower sideband sweep measurement light are coherently superimposed to generate a lower sideband ranging signal. The lower sideband ranging signal is then photoelectrically converted by the second photodetector to obtain a lower sideband ranging electrical signal, which enters the synchronous acquisition card. The second upper and lower sideband nonlinear sweep light is passed through the FP etalon to obtain a nonlinear sweep interference light signal, which is then transmitted to the third photodetector. The nonlinear swept frequency interference optical signal is converted into a nonlinear swept frequency interference electrical signal by the third photodetector and then enters the synchronous acquisition card. The synchronous acquisition card acquires the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear swept frequency interference electrical signal and transmits them to the demodulation module. The demodulation module obtains the real-time distance and velocity of the moving target based on the upper sideband ranging electrical signal, the lower sideband ranging electrical signal, and the nonlinear swept frequency interference electrical signal.

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