An efficient phase demodulation method based on special sampling rate

Abstract

The present invention discloses an efficient phase demodulation method based on a special sampling rate, including using a special sampling rate to ensure the spectral symmetry of the signal to be demodulated, so that the orthogonal signal pair of the heterodyne interference signal and the reference signal can be efficiently obtained only through a specific delay operation; the orthogonal signal pair obtained after a specific delay at a special sampling rate is cross-mixed and added and subtracted with a pair of reference signal orthogonal signal pairs to obtain an orthogonal signal pair directly related to the phase, and the phase demodulation result can be directly obtained through inverse tangent and phase unfolding. The present invention greatly simplifies the demodulation process, and the simulation experiment and experimental test results show that the demodulation scheme is particularly suitable for the calibration of laser vibrometers. Compared with traditional schemes, the present invention greatly reduces the requirements for digital processor performance, which is conducive to promoting the establishment of a new low-cost, high-precision laser interferometry underwater acoustic benchmark.

Description

Technical Field

[0001] The invention relates to the technical field of signal processing, and in particular to a high-efficiency phase demodulation method based on a special sampling rate. Background Art

[0002] Phase demodulation is a signal processing technique used to recover the original phase information from a modulated signal. In phase modulation (PM) or frequency modulation (FM), information is encoded in the phase changes of the carrier signal. The purpose of phase demodulation is to detect and recover this information from the changing phase. Therefore, phase demodulation is essential in general situations involving the need to extract information from modulated signals, especially in systems where the information is encoded in the phase changes.

[0003] Phase demodulation is a basic signal processing technique that is mainly used in the following areas: Wireless communications: Phase demodulation is a common technique in wireless communications to recover information from modulated signals. Cell phones, wireless local area networks (WLAN), satellite communications, and radio broadcasting all use phase modulation and demodulation techniques. Radar systems: Radar uses phase modulation to measure the distance and speed of target objects. In synthetic aperture radar (SAR) and other advanced radar technologies, phase demodulation is used to process echo signals to obtain high-resolution images. Fiber-optic communications: Phase modulation and demodulation techniques are also very important in fiber-optic communications, especially in coherent optical communication systems, where they can increase data transmission rates and link distances. Modems: In traditional telephone line modems and modern broadband modems, phase modulation and demodulation techniques are used to encode and decode digital data in analog signals. Audio and video broadcasting: Frequency modulation in FM broadcasting essentially involves continuous changes in phase, so phase demodulation is a key step in recovering audio signals at the receiver. Navigation systems: Phase modulation techniques are used in the Global Positioning System (GPS) and other satellite navigation systems to provide precise positioning information. The receiver must be able to demodulate these signals to calculate the exact position. Scientific and Engineering Research: Phase demodulation is used for signal analysis in experimental devices in physics, astronomy, and other scientific fields, such as the application of interferometers in optics and quantum computing. Commonly used phase demodulation techniques usually include digital IQ demodulation, Hilbert transform phase demodulation, dual lock-in amplifier demodulation, etc.

[0004] In order to obtain better filtering effect in digital IQ demodulation, the frequency response of the digital low-pass filter must be designed to be very flat, which will consume a lot of digital processor hardware resources.

[0005] In Hilbert transform phase demodulation, the flatness requirement for the Hilbert transform filter is high, so relatively high computing resources are needed, especially in real-time or high-speed data processing.

[0006] In SPS phase demodulation, the requirements for the data acquisition system are very high, and the interval between adjacent channels must be very small.

[0007] In view of the above problems, the present invention provides an efficient phase demodulation method based on a special sampling rate, which can reasonably select a special sampling rate according to the bandwidth of a signal to be demodulated. Summary of the invention

[0008] The present invention provides an efficient phase demodulation method based on a special sampling rate, which can reasonably select a special sampling rate according to the bandwidth of a signal to be demodulated.

[0009] The purpose of the present invention is to provide an efficient phase demodulation method based on a special sampling rate, and the specific steps of the method are as follows:

[0010] Step 1: An efficient phase demodulation method under a special sampling rate is used to demodulate the phase of the heterodyne interference signal, where the expression of the heterodyne interference signal is:

[0011]

[0012] Among them, u p is the signal amplitude, λ is the laser wavelength, f c are the carrier frequency and center frequency, φ s is the initial phase of the interference signal, v p is the vibration signal amplitude, f v is the vibration signal frequency, φ s is the initial phase of the vibration signal.

[0013] Furthermore, the efficient phase demodulation method under the special sampling rate in step 1 has the following specific steps:

[0014] Step 1: The Doppler signal and the reference signal are first filtered by an analog bandpass filter. The filter is used to filter out the frequency components outside the Carson bandwidth. The center frequency of the Doppler signal and the reference signal frequency are f c , so f s =4Nf c The sampling rate of / (2k-1) is used to sample the two signals simultaneously. The sampling rate must also satisfy:

[0015] f s >2·BW

[0016] Where BW is the signal bandwidth and:

[0017] BW=2(2v p / λ+f v )

[0018] Step 2: Input the sampled digital signal into the digital processor and remove the DC component from the two signals. After eliminating the DC component, the Doppler signal is delayed. The delay time depends on the center frequency and the sampling rate. If f c The frequency is 40MHz, and the sampling rate is 160MSPS, then N=1, that is, the Doppler signal is delayed by one clock cycle, and the delayed signal is represented by SIN(D), and the other signal is not delayed, and the signal is represented by COS(D). The reference signal is processed in the same way, and the signals SIN(R) and COS(R) are obtained respectively. Then, the four signals are processed as follows to obtain:

[0019]

[0020] Step 3: Perform arc tangent calculation and phase unwrapping on the processed signals SIN(DR) and COS(DR):

[0021]

[0022] Here, kπ is an additional phase and the value of k is an integer belonging to the set {0,1,2,...}.

[0023] Step 4: Perform appropriate CIC extraction filtering on the demodulated phase to reduce the data rate, and then filter out unnecessary high-frequency components through a digital low-pass filter.

[0024] The present invention has the following advantages: the present invention greatly simplifies the demodulation process. Simulation experiments and experimental test results show that the demodulation scheme is particularly suitable for the calibration of laser vibrometers. Compared with traditional schemes, the present invention greatly reduces the requirements for digital processor performance, which is conducive to promoting the establishment of a new low-cost, high-precision laser interferometry underwater acoustic benchmark.

[0025] The present invention is not only applicable to off-line phase signal demodulation, but also particularly applicable to real-time phase signal demodulation.

[0026] The present invention can efficiently obtain an orthogonal signal pair through a specific delay operation only at a special sampling rate, thereby achieving efficient phase demodulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a system block diagram of the efficient phase demodulation method under a special sampling rate of the present invention. DETAILED DESCRIPTION

[0028] The present invention provides an efficient phase demodulation method based on a special sampling rate, and the specific steps of the method are as follows:

[0029] Step 1: An efficient phase demodulation method under a special sampling rate is used to demodulate the phase of the heterodyne interference signal, where the expression of the heterodyne interference signal is:

[0030]

[0031] Among them, u p is the signal amplitude, λ is the laser wavelength, f c are the carrier frequency and center frequency, φ s is the initial phase of the interference signal, v p is the vibration signal amplitude, f v is the vibration signal frequency, φ s is the initial phase of the vibration signal.

[0032] In this embodiment, the efficient phase demodulation method under a special sampling rate in step 1 has the following specific steps:

[0033] Step 1: The Doppler signal and the reference signal are first filtered by an analog bandpass filter. The filter is used to filter out the frequency components outside the Carson bandwidth. The center frequency of the Doppler signal and the reference signal frequency are f c , so f s =4Nf c The sampling rate of / (2k-1) is used to sample the two signals simultaneously. The sampling rate must also satisfy:

[0034] f s >2·BW

[0035] Where BW is the signal bandwidth and:

[0036] BW=2(2v p / λ+f v )

[0037] Step 2: Input the sampled digital signal into the digital processor and remove the DC component from the two signals. After eliminating the DC component, the Doppler signal is delayed. The delay time depends on the center frequency and the sampling rate. If f c The frequency is 40MHz, and the sampling rate is 160MSPS, then N=1, that is, the Doppler signal is delayed by one clock cycle, and the delayed signal is represented by SIN(D), and the other signal is not delayed, and the signal is represented by COS(D). The reference signal is processed in the same way, and the signals SIN(R) and COS(R) are obtained respectively. Then, the four signals are processed as follows to obtain:

[0038]

[0039] Step 3: Perform arc tangent calculation and phase unwrapping on the processed signals SIN(DR) and COS(DR):

[0040]

[0041] Here, kπ is an additional phase and the value of k is an integer belonging to the set {0,1,2,...}.

[0042] Step 4: Perform appropriate CIC extraction filtering on the demodulated phase to reduce the data rate, and then filter out unnecessary high-frequency components through a digital low-pass filter.

[0043] Although the specific implementation of the present invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. An efficient phase demodulation method based on a special sampling rate, characterized in that: The method is used to demodulate the phase of a heterodyne interference signal, and the expression of the heterodyne interference signal is: ; ; u p is the signal amplitude, λ is the laser wavelength, f c are the carrier frequency and the center frequency, is the initial phase of the interference signal, v p is the vibration signal amplitude, f v is the vibration signal frequency, is the initial phase of the vibration signal; The specific steps of the efficient phase demodulation method based on special sampling rate are as follows: Step 1: The Doppler signal and the reference signal are first filtered by an analog bandpass filter to remove the frequency components outside the Carson bandwidth. The center frequency of the Doppler signal and the reference signal frequency are f c ,by f s =4Nf c / (2k-1) The two signals are sampled simultaneously at a sampling rate, and the sampling rate must also satisfy: ; in, BW is the signal bandwidth, and: ; Step 2: Input the sampled digital signal into the digital processor, remove the DC component of the two signals, and then delay the Doppler signal. The delay time depends on the center frequency and sampling rate. f c The sampling rate is 40 MHz f s For 160 MSPS, N =1, that is, the Doppler signal is delayed by one clock cycle, and the delayed signal is represented by SIN(D). The other signal is not delayed, and the signal is represented by COS(D). The reference signal is processed in the same way to obtain the signals SIN(R) and COS(R). Then the four signals are processed as follows to obtain: ; Step 3: Perform arc tangent calculation and phase unwrapping on the processed signals SIN(DR) and COS(DR): ; Where kπ is an additional phase, and the value of k is an integer belonging to the set {0, 1, 2, ...}; Step 4: Perform appropriate CIC extraction filtering on the demodulated phase to reduce the data rate, and then filter out unnecessary high-frequency components through a digital low-pass filter.

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