High-performance 3*3 coupler and PGC fusion improved demodulation method and device

Abstract

The invention discloses a high-performance 3 * 3 coupler and PGC fusion improved demodulation method and device, and the method comprises the steps: dividing an initial measured interference signal into three paths of initial to-be-measured signals through the 3 * 3 coupler, carrying out the operation of the three paths of initial to-be-measured signals, introducing frequency doubling signals of two paths of carrier signals and corresponding sine frequency doubling signals with the same frequency, and carrying out the calculation of the three paths of initial to-be-measured signals; useless higher harmonic components are all filtered out after the three paths of initial signals to be measured pass through a low-pass filter, and the influence of carrier phase delay, light intensity disturbance and modulation depth on a demodulation result is eliminated through certain mathematical calculation. According to the invention, the influence of light intensity disturbance, carrier phase delay and modulation depth is eliminated, and the detection sensitivity and anti-interference capability of tiny signals are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of signal demodulation, and in particular relates to a high-performance 3×3 coupler and PGC fusion improved demodulation method and device. Background Art

[0002] The 3×3 coupler demodulation method has many advantages such as high sensitivity, low signal loss, high adaptability, and strong anti-interference ability, while the Phase Generation Carrier (PGC) demodulation technology has many advantages such as large dynamic range, high sensitivity, and strong signal fidelity. Therefore, these two algorithms are widely used in high-precision and high anti-interference measurements of distributed optical fiber sensors, hydrophones, interferometers and other instruments and equipment. The 3×3 coupler demodulation method is to achieve phase demodulation by introducing a 3×3 coupler with a 120o phase difference between the two arms and combining it with an interference structure; while the PGC demodulation technology suppresses low-frequency noise by introducing a high-frequency carrier modulation signal, and then restores the original signal to be measured through calculation. It is mainly divided into the arctangent (Arctangent, PGC-Arctan) algorithm and the differential cross multiplication (Differential Cross Multiplication, PGC-DCM) algorithm.

[0003] However, the 3×3 coupler demodulation method is limited by its structure and other factors. The output signal is easily affected by light intensity disturbance or polarization fading, resulting in the three-way output phase not forming 120°, and the demodulation effect is poor; the differential cross-multiplication algorithm and the inverse tangent algorithm are very sensitive to light intensity disturbance, carrier phase delay and modulation depth fluctuation. In addition, since the inverse tangent algorithm divides the orthogonal components of the two mixed channels through a low-pass filter to obtain the tangent value, and then performs the inverse tangent operation to restore the signal to be measured, this method can only be used in When working within a range, jumps will occur at the range boundary, making it difficult to demodulate signals outside the range.

[0004] In order to improve the demodulation accuracy of the demodulation results, and at the same time improve the system's sensitivity to tiny signal detection and the anti-interference of the demodulation algorithm, it is generally only possible to upgrade the structure of the sensing system in hardware or improve the design of the calculation derivation process. Most of the existing improved algorithms can only eliminate the influence of some of these factors. For example, the invention with publication number CN110411334B proposes an improved phase carrier PGC demodulation method, which eliminates the influence of carrier phase delay and solves the problem that the interference signal will be out of sync with the frequency-multiplied signal due to analog-to-digital conversion; the 2022 article "Animproved PGC demodulation algorithm for optical fiber interferometers withinsensitive to carrier phase delay and modulation depth" proposes an improved algorithm based on PGC-DCM that eliminates the influence of carrier phase delay and simultaneously compensates for modulation depth. There are few methods that can eliminate three factors at the same time. To address this problem, the invention with publication number CN118353539A proposes a high-performance phase-generated carrier demodulation method and device. However, although the invention can eliminate the influence of three disturbance factors at the same time, it does not take into account the detection sensitivity and anti-interference performance of tiny signals. Summary of the invention

[0005] In order to solve the problem that the existing demodulation technology is difficult to simultaneously eliminate the three influencing factors of light intensity interference, carrier phase delay and modulation depth, and enhance the ability to detect small signals, while improving the demodulation accuracy and system stability, the present invention proposes a high-performance 3×3 coupler and PGC fusion improved demodulation method and device, which uses a 3×3 coupler and PGC fusion improved demodulation method to demodulate the signal to be measured from three initial interference signals, which not only eliminates the influence of the three factors of light intensity interference, carrier phase delay and modulation depth on the demodulation result, but also introduces a 3×3 coupler structure to amplify the small signal, improve the small signal detection sensitivity and phase demodulation accuracy, and enhance the anti-interference ability. It can be widely used in perimeter security, track monitoring, large-scale infrastructure building health monitoring and other fields.

[0006] Technical solution:

[0007] In a first aspect, the present invention discloses a high-performance 3×3 coupler and PGC fusion improved demodulation method, the demodulation method comprising the following steps:

[0008] The initial measured interference signal outputs three signals I1(t), I2(t) and I3(t) through a 3×3 coupler, where:

[0009] The first measured interference signal I1(t) is divided into two paths after passing through the first DC filter. The two signals are mixed with the first and second frequencies of the carrier signal respectively. The two mixed signals are filtered by a low-frequency filter to obtain a first filtered signal L1 and a second filtered signal L2.

[0010] The second measured interference signal I2(t) is divided into three paths after passing through the second DC filter. One signal is directly filtered by a low-pass filter to obtain a third filtered signal L3. The other two signals are mixed with the single-time sine and double-time sine signals of the carrier signal respectively. Both mixed signals are filtered by low-pass filters to obtain a fourth filtered signal L4 and a fifth filtered signal L5.

[0011] The third measured interference signal I3(t) is divided into two paths after passing through the third DC filter. The two signals are mixed with the one-time frequency and the two-time frequency of the carrier signal respectively. The two mixed signals are filtered by a low-frequency filter to obtain a sixth filtered signal L6 and a seventh filtered signal L7.

[0012] S2. The first filtered signal L1 is added to the sixth filtered signal L6 and then squared, and then added to the square of the fourth filtered signal L4 to obtain a first carrier-free phase-delayed square signal S1, the second filtered signal L2 is added to the seventh filtered signal L7 and then squared, and then added to the square of the fifth filtered signal L5 to obtain a second carrier-free phase-delayed square signal S2;

[0013] S3. Perform square root operations on the first carrier-free phase-delayed square signal S1 and the second carrier-free phase-delayed square signal S2 respectively to obtain a first carrier-free phase-delayed signal K1 and a second carrier-free phase-delayed signal K2, wherein the first carrier-free phase-delayed signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier-free phase-delayed signal K2 and the third filtered signal L3 are added to obtain a second operation result D2, and the first operation result D1 is divided by the second operation result D2 to obtain a third operation result D3;

[0014] S4. Multiply the third operation result D3 by 2 / C to obtain a signal V that eliminates the influence of modulation depth;

[0015] S5. Integrate the signal V that eliminates the influence of modulation depth, and obtain the phase signal of the signal to be measured after filtering out the high-frequency noise.

[0016] Further, in step S1, the three initial measured interference signals I1(t), I2(t) and I3(t) output by the 3×3 coupler are respectively:

[0017]

[0018] Where m is the amplitude of the light intensity disturbance, ωn is the angular frequency of the light intensity disturbance, t is the time, A is the DC component of the light intensity, B is the amplitude of the initial interference signal, C is the modulation depth, ω c is the angular frequency of the carrier modulation signal, θ is the carrier phase delay, is the phase signal of the signal to be measured at time t;

[0019] The expressions of the first filtered signal L1 and the second filtered signal L2 are respectively:

[0020]

[0021] Where, J1(C) is the first-order Bessel function, and J2(C) is the second-order Bessel function;

[0022] The expressions of the third filtered signal L3, the fourth filtered signal L4 and the fifth filtered signal L5 are respectively:

[0023]

[0024] Where, J0(C) is the zero-order Bessel function;

[0025] The expressions of the sixth filtered signal L6 and the seventh filtered signal L7 are respectively:

[0026]

[0027] Further, in step S2, the expressions of the first carrier-free phase-delayed square signal S1 and the second carrier-free phase-delayed square signal S2 are respectively:

[0028]

[0029] Further, in step S3, the expressions of the first carrier-free phase-delayed signal K1 and the second carrier-free phase-delayed signal K2 are respectively:

[0030]

[0031] The expressions of the first operation result D1, the second operation result D2 and the third operation result D3 are respectively:

[0032]

[0033] Further, in step S4, the expression for eliminating the modulation depth influence signal V is:

[0034]

[0035] In the second aspect, the present invention discloses a high-performance 3×3 coupler and PGC fusion improved demodulation device, the demodulation device includes a first DC filter, a second DC filter, a third DC filter, a third low-pass filter, a mixing filter module, a carrier phase delay elimination module, an optical intensity disturbance elimination module, a modulation depth influence elimination module, an integration module and a high-pass filter module;

[0036] The output end of the first DC filter divides the signal into two paths and enters the mixing filter module; the output end of the second DC filter divides the signal into three paths, one path enters the third low-pass filter, and the remaining two paths enter the mixing filter module; the output end of the third DC filter divides the signal into two paths and enters the mixing filter module; the third low-pass filter module is used to filter out the high-frequency components of the incoming signal to obtain the third filtered signal L3; the mixing filter module is used to mix and filter out the high-frequency components of the six input signals to obtain the first filtered signal L1, the second filtered signal L2, the fourth filtered signal L4 and the fifth filtered signal L5, the sixth filtered signal L6, and the seventh filtered signal L7;

[0037] The input end of the carrier phase delay elimination module is connected to the output end of the mixing filter module, and is used to respectively add the first filter signal L1 and the sixth filter signal L6 and then square them, and then add them to the square of the fourth filter signal L4 to obtain a first carrier-free phase delayed square signal S1, and add the second filter signal L2 and the seventh filter signal L7 and then square them, and then add them to the square of the fifth filter signal L5 to obtain a second carrier-free phase delayed square signal S2;

[0038] The input end of the light intensity disturbance elimination module is respectively connected to the output end of the third low-pass filter and the carrier phase delay elimination module, and square root operations are respectively performed on the first carrier-free phase delay square signal S1 and the second carrier-free phase delay square signal S2 to obtain the first carrier-free phase delay signal K1 and the second carrier-free phase delay signal K2, wherein the first carrier-free phase delay signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier-free phase delay signal K2 and the third filtered signal L3 are added to obtain a second operation result D2, and the first operation result D1 is divided by the second operation result D2 to obtain a third operation result D3;

[0039] The input end of the modulation depth influence elimination module is connected to the output end of the light intensity disturbance elimination module, and is used to multiply the third operation result D3 by 2 / C to obtain a modulation depth influence elimination signal V;

[0040] The input end of the integration module is connected to the output end of the modulation depth elimination module to restore the demodulated signal;

[0041] The input end of the high-pass filter module is connected to the output end of the integration module, and is used to filter out the low-frequency noise signal in the demodulated signal.

[0042] Further, the mixing and filtering module includes a first multiplier, a second multiplier, a third multiplier, a fourth multiplier, a fifth multiplier, a sixth multiplier, a digital frequency synthesizer, a first low-pass filter, a second low-pass filter, a fourth low-pass filter, a fifth low-pass filter, a sixth low-pass filter and a seventh low-pass filter;

[0043] One of the input ends of the first multiplier and the second multiplier is connected to the first DC filter, and the other input end is respectively connected to the single-frequency reference signal output end and the double-frequency reference signal output end of the digital frequency synthesizer, for mixing the two DC-filtered signals with the two double-frequency signals; one of the input ends of the third multiplier and the fourth multiplier is connected to the second DC filter, and the other input end is respectively connected to the single-frequency sinusoidal signal output end and the double-frequency sinusoidal signal output end of the digital frequency synthesizer, for mixing the two DC-filtered signals with the two double-frequency signals; one of the input ends of the fifth multiplier and the sixth multiplier is connected to the third DC filter, and the other input end is respectively connected to the single-frequency reference signal output end and the double-frequency reference signal output end of the digital frequency synthesizer, for mixing the two DC-filtered signals with the two double-frequency signals;

[0044] The output ends of the first multiplier, the second multiplier, the third multiplier, the fourth multiplier, the fifth multiplier and the sixth multiplier are respectively connected to the input ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter, for performing low-pass filtering operations on the six-channel mixing signals to obtain filtered signals of the phases of the six-channel signals to be measured, and the output ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter are connected to the module for eliminating carrier phase delay.

[0045] Further, the carrier phase delay elimination module includes: a first adder, a second adder, a third adder, a fourth adder, a first squarer, a second squarer, a third squarer and a fourth squarer;

[0046] The first input terminal of the first adder is connected to the output terminal of the first low-pass filter, the second input terminal is connected to the output terminal of the sixth low-pass filter, and the output terminal is connected to the input terminal of the first squarer; the first input terminal of the second adder is connected to the output terminal of the second low-pass filter, the second input terminal is connected to the output terminal of the seventh low-pass filter, and the output terminal is connected to the input terminal of the third squarer; the output terminal of the first squarer is connected to the first input terminal of the third adder; the input terminal of the second squarer is connected to the output terminal of the fourth low-pass filter, and the output terminal is connected to the second input terminal of the third adder; the output terminal of the third squarer is connected to the first input terminal of the fourth adder; the input terminal of the fourth squarer is connected to the output terminal of the fifth low-pass filter, and the output terminal is connected to the second input terminal of the fourth adder;

[0047] The output terminals of the third adder and the fourth adder are connected to a light intensity disturbance elimination module.

[0048] Further, the light intensity disturbance elimination module includes: a first square rooter, a second square rooter, a fifth adder, a first differentiator and a first divider;

[0049] The input end of the first square rooter is connected to the output end of the third adder; the input end of the second square rooter is connected to the output end of the fourth adder; the input end of the first differentiator is connected to the output end of the first square rooter, and the output end is connected to the first input end of the first divider; the first input end of the fifth adder is connected to the output end of the third low-pass filter, the second input end is connected to the output end of the second square rooter, and the output end is connected to the second input end of the first divider;

[0050] The output terminal of the first divider is connected to a module for eliminating the influence of modulation depth.

[0051] Further, the module for eliminating the influence of modulation depth includes: a first constant unit, a seventh multiplier;

[0052] The first input terminal of the seventh multiplier is connected to the first constant unit, the second input terminal is connected to the output terminal of the first divider, and the output terminal is connected to the input terminal of the integration module.

[0053] The output end of the integration module is connected to a high-pass filtering module.

[0054] Beneficial effects:

[0055] The high-performance 3×3 coupler and PGC fusion improved demodulation method and device of the present invention divides the initial measured interference signal into three initial test signals through the 3×3 coupler, performs operations on the three initial test signals, and then introduces the doubled frequency signals of two carrier signals and the corresponding sinusoidal doubled frequency signals of the same frequency, so that the three initial test signals can filter out all useless high-order harmonic components after passing through the low-pass filter, and then eliminate the influence of carrier phase delay, light intensity disturbance and modulation depth on the demodulation result through certain mathematical calculations; the present invention not only eliminates the influence of the three factors of light intensity interference, carrier phase delay and modulation depth on the demodulation result, but also amplifies the tiny signal by introducing the 3×3 coupler structure, improves the tiny signal detection sensitivity and phase demodulation accuracy, and enhances the anti-interference performance, and can be widely used in perimeter security, track monitoring, large-scale infrastructure building health monitoring and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a structural schematic diagram of the high-performance 3×3 coupler and PGC fusion improved demodulation device of the present invention.

[0057] Figure 2 It is a flow chart of the high-performance 3×3 coupler and PGC fusion improved demodulation method of the present invention.

[0058] Figure 3 It is a schematic diagram of the demodulation result of the present invention when the initial amplitude of the signal to be measured is 1.5 rad and the frequency is 500 Hz.

[0059] Figure 4 It is a schematic diagram of the demodulation results of the present invention at different modulation depths.

[0060] Figure 5 It is a schematic diagram of the demodulation results of the present invention under different light intensity disturbances (different amplitudes and frequencies).

[0061] Figure 6 It is a schematic diagram of the demodulation results of the present invention under different carrier phase delays.

[0062] Figure 7 It is a schematic diagram of the demodulation result of the present invention when the initial amplitude of the signal to be measured is 0.1 rad and the frequency is 500 Hz. DETAILED DESCRIPTION

[0063] The following examples will enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0064] See also Figure 2 This embodiment discloses a high-performance 3×3 coupler and PGC fusion improved demodulation method, including the following steps:

[0065] S1. The initial measured interference signal outputs three signals through the 3×3 coupler, which are collected by the data acquisition card after passing through the photoelectric detector. They are I1(t), I2(t) and I3(t). The expressions are as follows, which include three different influencing factors: light intensity disturbance, modulation depth and carrier phase delay:

[0066] First route:

[0067] Second route:

[0068] Third Road:

[0069] Where m is the amplitude of the light intensity disturbance, ω n is the angular frequency of the light intensity disturbance, t is the time, A is the DC component of the light intensity, B is the amplitude of the initial interference signal, C is the modulation depth, ω c is the angular frequency of the carrier modulation signal, θ is the carrier phase delay, is the phase signal of the signal to be measured at time t;

[0070] The first measured interference signal I1(t) is divided into two paths after passing through the first DC filter, and is mixed with the first and second frequencies of the carrier signal respectively, and then both paths are filtered through a low-pass filter to obtain two filtered signals, namely the first filtered signal L1 and the second filtered signal L2;

[0071]

[0072] Where, J1(C) is the first-order Bessel function, and J2(C) is the second-order Bessel function;

[0073] The second measured interference signal I2(t) is divided into three paths after passing through the second DC filter. One path is directly filtered by a low-pass filter to obtain a third filtered signal L3. The other two paths are mixed with the single-time sine and double-time sine signals of the carrier signal respectively, and then both paths are filtered by a low-pass filter to obtain two filtered signals, namely a fourth filtered signal L4 and a fifth filtered signal L5.

[0074]

[0075] Where, J0(C) is the zero-order Bessel function;

[0076] The third measured interference signal I3(t) is divided into two paths after passing through the third DC filter, and is mixed with the first and second frequencies of the carrier signal respectively, and then both paths are filtered through a low-pass filter to obtain two filtered signals, namely the sixth filtered signal L6 and the seventh filtered signal L7;

[0077]

[0078] S2. Eliminate carrier phase delay

[0079] The first filter signal L1 and the sixth filter signal L6 are added and then squared, and then added to the square of the fourth filter signal L4 to obtain a first carrier-free phase-delayed square signal S1; the second filter signal L2 and the seventh filter signal L7 are added and then squared, and then added to the square of the fifth filter signal L5 to obtain a second carrier-free phase-delayed square signal S2;

[0080]

[0081] S3. Eliminate light intensity disturbance

[0082] Performing square root operations on the first carrier-free phase-delayed square signal S1 and the second carrier-free phase-delayed square signal S2, respectively, to obtain a first carrier-free phase-delayed signal K1 and a second carrier-free phase-delayed signal K2, wherein the first carrier-free phase-delayed signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier-free phase-delayed signal K2 and the third filtered signal L3 are added to obtain a second operation result D2, and the first operation result D1 is divided by the second operation result D2 to obtain a third operation result D3;

[0083]

[0084] The expressions of the first operation result D1, the second operation result D2 and the third operation result D3 are respectively:

[0085]

[0086] S4. Eliminate the influence of modulation depth

[0087] Multiply the third operation result D3 by 2 / C to obtain a modulation depth-eliminated signal V;

[0088]

[0089] S5. Integrate the signal V that eliminates the influence of modulation depth, and finally filter out the high-frequency noise to obtain the phase signal of the signal to be measured.

[0090] In this embodiment, the effective bandwidth BW of the carrier frequency effective =2f m , f m Is the highest frequency of the carrier signal. The bandwidth of the low-pass filter is BW LP =f cut To ensure that the desired signal can pass, the cutoff frequency f cut Usually choose f cut ≥fmax , where f max is the highest frequency of the signal to be measured. As a preferred solution, in order to ensure that the filter can retain the main components of the signal, set f cut =2f max or cut =f max +Δf, Δf is to ensure that the filter has enough bandwidth to cover the characteristics of the signal. For example, set the sampling rate to 200kHz, the frequency of the signal to be measured to 500Hz, the amplitude to 2rad, and the carrier signal frequency to 10kHz. According to the above parameters, it can be determined that the effective bandwidth of the carrier frequency is 60kHz, the low-pass filter bandwidth is specified to be 1kHz, and the FIR low-pass filter with Hamming window is selected to achieve it.

[0091] See also Figure 1 This embodiment discloses a high-performance 3×3 coupler and PGC fusion improved demodulation device, which includes a first DC filter, a second DC filter, a third DC filter, a third low-pass filter, a mixing filter module, a carrier phase delay elimination module, an optical intensity disturbance elimination module, a modulation depth influence elimination module, an integration module and a high-pass filter module;

[0092] The output end of the first DC filter divides the signal into two paths and enters the mixing filter module; the output end of the second DC filter divides the signal into three paths, one path enters the third low-pass filter, and the remaining two paths enter the mixing filter module; the output end of the third DC filter divides the signal into two paths and enters the mixing filter module;

[0093] The output terminal of the third low-pass filter is connected to the light intensity disturbance elimination module, which is used to filter out the high-frequency component of the initial measured interference signal entering; the output terminal of the mixing filter module is connected to the carrier phase delay elimination module, which is used to mix the six DC filtered input signals and filter out the high-frequency components; the output terminal of the carrier phase delay elimination module is connected to the light intensity disturbance elimination module, which is used to eliminate the carrier phase delay in the demodulated signal; the output terminal of the light intensity disturbance elimination module is connected to the modulation depth influence elimination module, which is used to eliminate the light intensity disturbance in the demodulated signal; the output terminal of the modulation depth influence elimination module is connected to the integration module, which is used to eliminate the influence of the modulation depth on the demodulated signal; the output terminal of the integration module is connected to the high-pass filter module, which is used to restore the demodulated signal; the high-pass filter module is used to filter out the low-frequency noise signal in the demodulated signal.

[0094] The frequency mixing and filtering module of this embodiment includes first to sixth multipliers, a digital frequency synthesizer, a first low-pass filter, a second low-pass filter, a fourth low-pass filter, a fifth low-pass filter, a sixth low-pass filter and a seventh low-pass filter.

[0095] The input terminal I of the first multiplier and the second multiplier are connected to the first DC filter, and the input terminal II is respectively connected to the single-frequency reference signal output terminal and the double-frequency reference signal output terminal of the digital frequency synthesizer, so as to mix the two DC-filtered signals with the two double-frequency signals; the input terminal I of the third multiplier and the fourth multiplier are connected to the second DC filter, and the input terminal II is respectively connected to the single-frequency sinusoidal signal output terminal and the double-frequency sinusoidal signal output terminal of the digital frequency synthesizer, so as to mix the two DC-filtered signals with the two double-frequency signals; the input terminal I of the fifth multiplier and the sixth multiplier are connected to the third DC filter, and the input terminal II is respectively connected to the single-frequency reference signal output terminal and the double-frequency reference signal output terminal of the digital frequency synthesizer, so as to mix the two DC-filtered signals with the two double-frequency signals.

[0096] The output ends of the first multiplier, the second multiplier, the third multiplier, the fourth multiplier, the fifth multiplier and the sixth multiplier are respectively connected to the input ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter, for performing low-pass filtering operations on the six-channel mixing signals to obtain filtered signals of the phases of the six-channel signals to be measured, and the output ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter are connected to the module for eliminating carrier phase delay.

[0097] The carrier phase delay elimination module of this embodiment includes: a first adder, a second adder, a third adder, a fourth adder, a first squarer, a second squarer, a third squarer and a fourth squarer.

[0098] The input terminal I of the first adder is connected to the output terminal of the first low-pass filter, the input terminal II is connected to the output terminal of the sixth low-pass filter, and the output terminal is connected to the input terminal of the first squarer; the input terminal I of the second adder is connected to the output terminal of the second low-pass filter, the input terminal II is connected to the output terminal of the seventh low-pass filter, and the output terminal is connected to the input terminal of the third squarer; the output terminal of the first squarer is connected to the input terminal I of the third adder; the input terminal of the second squarer is connected to the output terminal of the fourth low-pass filter, and the output terminal is connected to the input terminal II of the third adder; the output terminal of the third squarer is connected to the input terminal I of the fourth adder; the input terminal of the fourth squarer is connected to the output terminal of the fifth low-pass filter, and the output terminal is connected to the input terminal II of the fourth adder; the output terminals of the third adder and the fourth adder are connected to the light intensity disturbance elimination module.

[0099] The light intensity disturbance elimination module of this embodiment includes: a first square rooter, a second square rooter, a fifth adder, a first differentiator and a first divider.

[0100] The input end of the first square rooter is connected to the output end of the third adder; the input end of the second square rooter is connected to the output end of the fourth adder; the input end of the first differentiator is connected to the output end of the first square rooter, and the output end is connected to the input end I of the first divider; the input end I of the fifth adder is connected to the output end of the third low-pass filter, the input end II is connected to the output end of the second square rooter, and the output end is connected to the input end II of the first divider; the output end of the first divider is connected to the module for eliminating the influence of modulation depth.

[0101] The module for eliminating the influence of modulation depth in this embodiment includes: a first constant unit and a seventh multiplier.

[0102] The input terminal I of the seventh multiplier is connected to the first constant unit, the input terminal II is connected to the output terminal of the first divider, and the output terminal is connected to the input terminal of the integration module.

[0103] The output end of the integration module is connected to a high-pass filter module, and the low-frequency noise is filtered out by the high-pass filter module to obtain the phase to be measured.

[0104] In order to verify the beneficial effects of the present invention, the inventors used the above-mentioned high-performance 3×3 coupler and PGC fusion to improve the demodulation method and device to make the following embodiments:

[0105] Example 1

[0106] Set the initial measured signal amplitude to 1.5 rad, frequency to 500 Hz, carrier modulation signal frequency to 20 kHz, modulation depth to 2 rad, sampling rate to 200 kHz, light intensity DC component to 1 rad, interference signal amplitude to 1 rad, and the measured signal to be Figure 3 As shown in (a) in the figure, the demodulation result is Figure 3 As shown in (b) of Figure 3 It can be seen that the improved demodulation method and device combining the 3×3 coupler and PGC of the present invention can restore the signal to be measured.

[0107] Example 2

[0108] Set the initial amplitude of the signal to be tested to 1.5 rad, the frequency to 200 Hz, the carrier modulation signal frequency to 20 kHz, the sampling rate to 200 kHz, the DC component of the light intensity to 1 rad, the interference signal amplitude to 1 rad, and the modulation depths to 1.5 rad, 2.37 rad, 2.63 rad, and 3.6 rad, respectively. The signal to be tested is as follows: Figure 4 As shown in (a) in the figure, the demodulation result is Figure 4 As shown in (b) of Figure 4 It can be seen that the 3×3 coupler and PGC fusion improved demodulation method and device of the present invention are not sensitive to changes in the modulation depth C.

[0109] Example 3

[0110] Set the initial measured signal amplitude to 1.5 rad, frequency to 200 Hz, carrier modulation signal frequency to 20 kHz, modulation depth to 2 rad, sampling rate to 200 kHz, light intensity DC component to 1 rad, interference signal amplitude to 1 rad, light intensity disturbance amplitude to 1 rad, 2 rad, frequency to 10 Hz and 20 Hz respectively. The measured signal is as follows: Figure 5 As shown in (a) in the figure, the demodulation result is Figure 5 As shown in (b) of Figure 5 It can be seen that the 3×3 coupler and PGC fusion improved demodulation method and device of the present invention are not affected by light intensity disturbance.

[0111] Example 4

[0112] Set the initial measured signal amplitude to 1.5 rad, frequency to 200 Hz, carrier modulation signal frequency to 20 kHz, modulation depth to 2 rad, sampling rate to 200 kHz, light intensity DC component to 1 rad, interference signal amplitude to 1 rad, and carrier phase delay to 23°, 67°, and 114° respectively. The measured signal is as follows: Figure 6 As shown in (a) in the figure, the demodulation result is Figure 6 As shown in (b) of Figure 6 It can be seen that the 3×3 coupler and PGC fusion improved demodulation method and device of the present invention can eliminate the influence of carrier phase delay on the demodulation result.

[0113] Example 5

[0114] Set the initial measured signal amplitude to 0.1 rad, frequency to 500 Hz, carrier modulation signal frequency to 20 kHz, modulation depth to 2 rad, sampling rate to 200 kHz, light intensity DC component to 1 rad, interference signal amplitude to 1 rad, and the measured signal to be Figure 7 As shown in (a) in the figure, the demodulation result is Figure 7 As shown in (b) of Figure 7 It can be seen that the improved demodulation method and device combining the 3×3 coupler and PGC of the present invention can restore the signal to be measured.

[0115] In summary, the high-performance 3×3 coupler and PGC fusion improved demodulation method and device of the present invention obtains a relationship that does not include the three factors of light intensity disturbance, carrier phase delay and modulation depth, and can determine the phase of the signal to be measured. The final restored phase signal is not affected by the above three factors, and can effectively improve the phase demodulation accuracy and demodulation stability.

[0116] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A high-performance 3×3 coupler and PGC fusion improved demodulation method, characterized in that: The demodulation method comprises the following steps: The initial measured interference signal outputs three signals I1(t), I2(t) and I3(t) through a 3×3 coupler, where: The first measured interference signal I1(t) is divided into two paths after passing through the first DC filter. The two signals are mixed with the first and second frequencies of the carrier signal respectively. The two mixed signals are filtered by a low-frequency filter to obtain a first filtered signal L1 and a second filtered signal L2. The second measured interference signal I2(t) is divided into three paths after passing through the second DC filter. One signal is directly filtered by a low-pass filter to obtain a third filtered signal L3. The other two signals are mixed with the single-time sine and double-time sine signals of the carrier signal respectively. Both mixed signals are filtered by low-pass filters to obtain a fourth filtered signal L4 and a fifth filtered signal L5. The third measured interference signal I3(t) is divided into two paths after passing through the third DC filter. The two signals are mixed with the one-time frequency and the two-time frequency of the carrier signal respectively. The two mixed signals are filtered by a low-frequency filter to obtain a sixth filtered signal L6 and a seventh filtered signal L7. S2. The first filtered signal L1 is added to the sixth filtered signal L6 and then squared, and then added to the square of the fourth filtered signal L4 to obtain a first carrier-free phase-delayed square signal S1, the second filtered signal L2 is added to the seventh filtered signal L7 and then squared, and then added to the square of the fifth filtered signal L5 to obtain a second carrier-free phase-delayed square signal S2; S3. Perform square root operations on the first carrier-free phase-delayed square signal S1 and the second carrier-free phase-delayed square signal S2 respectively to obtain a first carrier-free phase-delayed signal K1 and a second carrier-free phase-delayed signal K2, wherein the first carrier-free phase-delayed signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier-free phase-delayed signal K2 and the third filtered signal L3 are added to obtain a second operation result D2, and the first operation result D1 is divided by the second operation result D2 to obtain a third operation result D3; S4. Multiply the third operation result D3 by 2 / C to obtain a signal V that eliminates the influence of modulation depth; S5. Integrate the signal V that eliminates the influence of modulation depth, and obtain the phase signal of the signal to be measured after filtering out the high-frequency noise.

2. According to claim 1, the high-performance 3×3 coupler and PGC fusion improved demodulation method is characterized in that: In step S1, the three initial measured interference signals I1(t), I2(t) and I3(t) output by the 3×3 coupler are respectively: Where m is the amplitude of the light intensity disturbance, ω n is the angular frequency of the light intensity disturbance, t is the time, A is the DC component of the light intensity, B is the amplitude of the initial interference signal, C is the modulation depth, ω c is the angular frequency of the carrier modulation signal, θ is the carrier phase delay, is the phase signal of the signal to be measured at time t; The expressions of the first filtered signal L1 and the second filtered signal L2 are respectively: Where, J1(C) is the first-order Bessel function, and J2(C) is the second-order Bessel function; The expressions of the third filtered signal L3, the fourth filtered signal L4 and the fifth filtered signal L5 are respectively: Where, J0(C) is the zero-order Bessel function; The expressions of the sixth filtered signal L6 and the seventh filtered signal L7 are respectively:

3. The high-performance 3×3 coupler and PGC fusion improved demodulation method according to claim 1 is characterized in that: In step S2, the expressions of the first carrier-free phase-delayed square signal S1 and the second carrier-free phase-delayed square signal S2 are respectively:

4. The high-performance 3×3 coupler and PGC fusion improved demodulation method according to claim 1 is characterized in that: In step S3, the expressions of the first carrier-free phase-delayed signal K1 and the second carrier-free phase-delayed signal K2 are respectively: The expressions of the first operation result D1, the second operation result D2 and the third operation result D3 are respectively:

5. The high-performance 3×3 coupler and PGC fusion improved demodulation method according to claim 1 is characterized in that: In step S4, the expression for eliminating the modulation depth influence signal V is:

6. A high-performance 3×3 coupler and PGC fusion improved demodulation device, characterized in that: The demodulation device includes a first DC filter, a second DC filter, a third DC filter, a third low-pass filter, a frequency mixing filter module, a carrier phase delay elimination module, a light intensity disturbance elimination module, a modulation depth influence elimination module, an integration module and a high-pass filter module; The output end of the first DC filter divides the signal into two paths and enters the mixing filter module; the output end of the second DC filter divides the signal into three paths, one path enters the third low-pass filter, and the remaining two paths enter the mixing filter module; The output end of the third DC filter divides the signal into two paths and enters the mixing filter module; the third low-pass filter module is used to filter out the high-frequency component of the incoming signal to obtain a third filtered signal L3; The mixing and filtering module is used to mix and filter the six input signals to remove high-frequency components, and obtain a first filter signal L1, a second filter signal L2, a fourth filter signal L4, a fifth filter signal L5, a sixth filter signal L6, and a seventh filter signal L7; The input end of the carrier phase delay elimination module is connected to the output end of the mixing filter module, and is used to respectively add the first filter signal L1 and the sixth filter signal L6 and then square them, and then add them to the square of the fourth filter signal L4 to obtain a first carrier-free phase delayed square signal S1, and add the second filter signal L2 and the seventh filter signal L7 and then square them, and then add them to the square of the fifth filter signal L5 to obtain a second carrier-free phase delayed square signal S2; The input end of the light intensity disturbance elimination module is respectively connected to the output end of the third low-pass filter and the carrier phase delay elimination module, and square root operations are respectively performed on the first carrier-free phase delay square signal S1 and the second carrier-free phase delay square signal S2 to obtain the first carrier-free phase delay signal K1 and the second carrier-free phase delay signal K2, wherein the first carrier-free phase delay signal K1 is derived with respect to time t to obtain a first operation result D1, the second carrier-free phase delay signal K2 and the third filtered signal L3 are added to obtain a second operation result D2, and the first operation result D1 is divided by the second operation result D2 to obtain a third operation result D3; The input end of the modulation depth influence elimination module is connected to the output end of the light intensity disturbance elimination module, and is used to multiply the third operation result D3 by 2 / C to obtain a modulation depth influence elimination signal V; The input end of the integration module is connected to the output end of the modulation depth elimination module to restore the demodulated signal; The input end of the high-pass filter module is connected to the output end of the integration module, and is used to filter out the low-frequency noise signal in the demodulated signal.

7. The high-performance 3×3 coupler and PGC fusion improved demodulation device according to claim 6 is characterized in that: The mixing and filtering module includes a first multiplier, a second multiplier, a third multiplier, a fourth multiplier, a fifth multiplier, a sixth multiplier, a digital frequency synthesizer, a first low-pass filter, a second low-pass filter, a fourth low-pass filter, a fifth low-pass filter, a sixth low-pass filter and a seventh low-pass filter; One of the input ends of the first multiplier and the second multiplier is connected to the first DC filter, and the other input end is respectively connected to the single-frequency reference signal output end and the double-frequency reference signal output end of the digital frequency synthesizer, for mixing the two DC-filtered signals with the two double-frequency signals; one of the input ends of the third multiplier and the fourth multiplier is connected to the second DC filter, and the other input end is respectively connected to the single-frequency sinusoidal signal output end and the double-frequency sinusoidal signal output end of the digital frequency synthesizer, for mixing the two DC-filtered signals with the two double-frequency signals; one of the input ends of the fifth multiplier and the sixth multiplier is connected to the third DC filter, and the other input end is respectively connected to the single-frequency reference signal output end and the double-frequency reference signal output end of the digital frequency synthesizer, for mixing the two DC-filtered signals with the two double-frequency signals; The output ends of the first multiplier, the second multiplier, the third multiplier, the fourth multiplier, the fifth multiplier and the sixth multiplier are respectively connected to the input ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter, for performing low-pass filtering operations on the six-channel mixing signals to obtain filtered signals of the phases of the six-channel signals to be measured, and the output ends of the first low-pass filter, the second low-pass filter, the fourth low-pass filter, the fifth low-pass filter, the sixth low-pass filter and the seventh low-pass filter are connected to the module for eliminating carrier phase delay.

8. The high-performance 3×3 coupler and PGC fusion improved demodulation device according to claim 6 is characterized in that: The carrier phase delay elimination module comprises: a first adder, a second adder, a third adder, a fourth adder, a first squarer, a second squarer, a third squarer and a fourth squarer; The first input terminal of the first adder is connected to the output terminal of the first low-pass filter, the second input terminal is connected to the output terminal of the sixth low-pass filter, and the output terminal is connected to the input terminal of the first squarer; the first input terminal of the second adder is connected to the output terminal of the second low-pass filter, the second input terminal is connected to the output terminal of the seventh low-pass filter, and the output terminal is connected to the input terminal of the third squarer; the output terminal of the first squarer is connected to the first input terminal of the third adder; the input terminal of the second squarer is connected to the output terminal of the fourth low-pass filter, and the output terminal is connected to the second input terminal of the third adder; the output terminal of the third squarer is connected to the first input terminal of the fourth adder; the input terminal of the fourth squarer is connected to the output terminal of the fifth low-pass filter, and the output terminal is connected to the second input terminal of the fourth adder; The output terminals of the third adder and the fourth adder are connected to a light intensity disturbance elimination module.

9. The high-performance 3×3 coupler and PGC fusion improved demodulation device according to claim 6 is characterized in that: The light intensity disturbance elimination module comprises: a first square rooter, a second square rooter, a fifth adder, a first differentiator and a first divider; The input end of the first square rooter is connected to the output end of the third adder; the input end of the second square rooter is connected to the output end of the fourth adder; the input end of the first differentiator is connected to the output end of the first square rooter, and the output end is connected to the first input end of the first divider; the first input end of the fifth adder is connected to the output end of the third low-pass filter, the second input end is connected to the output end of the second square rooter, and the output end is connected to the second input end of the first divider; The output terminal of the first divider is connected to a module for eliminating the influence of modulation depth.

10. The high-performance 3×3 coupler and PGC fusion improved demodulation device according to claim 6 is characterized in that: The module for eliminating the influence of modulation depth includes: a first constant unit and a seventh multiplier; The first input terminal of the seventh multiplier is connected to the first constant unit, the second input terminal is connected to the output terminal of the first divider, and the output terminal is connected to the input terminal of the integration module. The output end of the integration module is connected to a high-pass filtering module.

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