A method for synthesizing and separating ultrasonic signals

Abstract

The present invention discloses a method for synthesizing and separating ultrasonic signals, providing a method for reducing the number of analog channels when a large-scale ultrasonic sensor array receives echo signals. The present invention performs frequency shifting on each ultrasonic echo signal, and the frequency bands of the modulated signals after each frequency shift are allowed to overlap. In the present invention, the carrier wave for frequency shifting is formed by D / A conversion of a discrete sequence generated by a digital device, avoiding the circuit complexity and low frequency control accuracy when an oscillating circuit is used to generate a carrier wave. At the same time, the generated carrier wave can be directly demodulated using a wavelet demodulation method during subsequent synthetic signal separation, avoiding the strict phase requirements for carrier waves of the same frequency during conventional demodulation, thereby reducing the difficulty of demodulation. The present invention can enable eight ultrasonic sensor echo signals to share one analog channel, and can separate the waveforms, echo delays, and amplitudes of the eight echo signals at the digital processing end.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrasonic nondestructive testing and relates to an ultrasonic signal synthesis and separation method. Background Art

[0002] In the field of modern ultrasonic nondestructive testing, ultrasonic sensors are developing towards arrays, even large-scale arrays. Increasing the number of array elements not only improves the efficiency of a single scan but also captures richer information about reflectors, enabling more accurate quantitative information on the spatial distribution of defects and more reliable evaluation of overall material performance. However, this increase in the number of array elements inevitably leads to an increase in the number of analog signal processing channels. Each ultrasonic sensor requires its own independent receiving circuit. As the array element size increases, the circuit complexity and manufacturing cost increase significantly.

[0003] To reduce the number of circuits in ultrasonic sensor signal processing units and improve channel utilization, current ultrasonic array signal reception and processing technology primarily synthesizes the signals received by the ultrasonic sensor according to a certain time and phase difference. Signal synthesis based on time division multiplexing can determine the echo delay range of different channels based on the sensor geometry and acoustic field transmission characteristics, enabling time-sharing synthesis of multi-channel sensor signals. However, this requires a priori propagation acoustic field geometry parameters, which makes detection inconvenient. Orthogonal synthesis of ultrasonic signals involves preprocessing the analog signals received by the ultrasonic sensor array elements, modulating the low-frequency components of the ultrasonic echo signal with a set of mutually orthogonal trigonometric functions, and then synthesizing the orthogonally modulated signals into one analog signal using an adder. However, the number of synthesized signals is limited.

[0004] Frequency division multiplexing (FDM) was originally used for signal transmission, enabling the simultaneous transmission of multiple signals within a single channel, with each signal overlapping in time but not in spectrum. FDM-based signal synthesis modulates the echo signals from multiple sensors into different frequency bands to achieve synthesis. However, this method requires setting frequency band spacing for each signal in the frequency domain, reducing the number of synthesized channels and bandwidth utilization, while also placing high bandwidth requirements on the device. The present invention aims to improve the utilization of ultrasonic receiving channels, increase the number of synthesized channels, and separate the key parameters of the original single channel from the synthesized signal. Summary of the Invention

[0005] To address the limitations of existing ultrasonic signal synthesis and separation technologies, the present invention provides a method for synthesizing and separating ultrasonic signals. This method uses analog circuitry to acquire ultrasonic transducer echo signals in real time and synthesizes these N-channel ultrasonic sensor echo signals, reducing circuit complexity. Furthermore, the N-channel ultrasonic signals of different frequencies do not require frequency band spacing, increasing the number of synthesized channels within the same bandwidth and improving frequency band utilization.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a method for synthesizing and separating ultrasonic signals, comprising the following contents:

[0007] Signal synthesis:

[0008] S1) Obtain the echo signal u detected by each ultrasonic sensor n (t), preprocess the echo signal to obtain the envelope signal x n (t);

[0009] S2) A discrete sequence g is generated by a digital device n (n), the discrete sequence is reshaped into a carrier signal g n (t);

[0010] S3) convert the N-channel ultrasonic sensor envelope signal x n (t) Carrier signal g with different frequencies from N groups n (t) Modulate through the modulation circuit to generate N modulated signals y with different frequencies but the same phase as the original signal n (t);

[0011] S4) The modulated N-channel ultrasonic sensor signal y n (t) Add through the adding circuit to synthesize a signal y ∑ (t);

[0012] S5) synthesize the signal y from the N ultrasonic sensors ∑ (t) Obtain the synthetic signal discrete digital sequence y through analog-to-digital conversion ∑ (k);

[0013] Signal separation:

[0014] In the host computer, the discrete sequence y of the digitized synthetic signal is ∑ (k) Perform wavelet packet decomposition and reconstruction to obtain each separated signal from The echo signal parameters are estimated.

[0015] Furthermore, in the above step S1), N ultrasonic sensors are used to perform ultrasonic testing on the material to be tested, and the echo signal u of each ultrasonic sensor is obtained. n (t),

[0016] u n (t) = h n (tt n )cos(2πf0(tt n )), n = 1, 2, ... N

[0017] Among them, h n(t) is the envelope of each ultrasonic echo signal, f0 is the center frequency of the ultrasonic sensor, t n is the echo arrival time.

[0018] Furthermore, in the above step S1), each ultrasonic sensor element echo signal u n (t) Perform noise reduction and envelope preprocessing to obtain the processed envelope signal x n (t),

[0019]

[0020] Among them, β n is the amplitude, α n is the form factor, t n is the echo arrival time.

[0021] Furthermore, in the above step S2), the digital device CPU or FPGA generates a discrete sequence g n (n), generate different frequencies f through D / A shaping circuit n The carrier signal g n (t),

[0022]

[0023] Among them, A n is the carrier signal amplitude, is the initial phase of the carrier signal.

[0024] Furthermore, in the above step S3), the envelope signal x n (t) and the carrier signal g n (t) Modulate the signal through the multiplication circuit to generate the modulated frequency shift signal y n (t),

[0025]

[0026] Among them, A n is the carrier signal amplitude, β n is the envelope signal amplitude, α n is the form factor, t n is the echo arrival time, f n is the frequency of the carrier signal, is the initial phase of the carrier signal.

[0027] Furthermore, in the above step S4), the N frequency-shifted signals y n (t) Through the adding circuit, synthesize a signal y ∑ (t),

[0028]

[0029] Furthermore, in the above step S5), the synthesized signal y ∑ (t) Perform A / D conversion to obtain the discrete digital sequence y of the synthetic signal ∑ (k), k = 0, 1, 2, ..., L-1, where L is the length of the sampled data, and the discrete digital sequence y ∑ (k) Transmit to the host computer.

[0030] Furthermore, in the above step S4), the first carrier frequency is the base frequency f1, and the maximum allowable bandwidth of the composite signal is B, then

[0031]

[0032] The remaining carrier frequencies are Sure;

[0033] The carrier frequency is f n The cosine signal of each channel is modulated, and the ultrasonic frequency bands in the synthetic signal overlap.

[0034] Furthermore, the above-mentioned synthetic signal discrete sequence y ∑ (k) Reconstruction includes: converting the synthetic sequence y ∑ (k) Decompose into N sub-bands, arrange the sub-bands from low to high according to frequency, and obtain the separated channel signal sequences in sequence from The time delay and amplitude of the echo signal are obtained.

[0035] The beneficial effects of the present invention are:

[0036] Unlike conventional frequency-division multiplexing signal synthesis methods, the analog signals received by N ultrasonic sensor array elements are first preprocessed and modulated with N groups of cosine signals with different center frequencies. The N ultrasonic sensor signals with different center frequencies are then synthesized into one analog signal using an adder. A synthesized ultrasonic echo digital signal is obtained through a single analog-to-digital conversion channel. With the help of wavelet packet decomposition, the parameters of the original signal can be separated. The beneficial effect of the present invention is that there is no need to set frequency band intervals for N ultrasonic sensor signals of different frequencies. Under the condition of the same bandwidth, the number of synthesized channels is increased, the utilization rate of the frequency band is improved, and single-channel acquisition is achieved for multi-channel ultrasonic sensor signals, reducing the circuit scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flowchart of the method of the present invention;

[0038] Figure 2 The time domain and frequency domain diagrams of the ultrasonic sensor echo signal in the embodiment of the present invention;

[0039] Figure 3This is a time-frequency diagram of the synthetic signal of 8 ultrasonic sensors in an embodiment of the present invention;

[0040] Figure 4 The time domain and frequency domain diagrams of the synthetic signals of 8 ultrasonic sensors with the same amplitude and the same defect position in the embodiment of the present invention are shown;

[0041] Figure 5 This is a waveform diagram of the frequency domain and time domain separation of the synthetic signal of 8 ultrasonic sensors with the same amplitude and the same defect position in an embodiment of the present invention;

[0042] Figure 6 The time domain and frequency domain diagrams of the synthetic signals of 8-channel ultrasonic sensors with the same amplitude and random defect positions in an embodiment of the present invention are shown;

[0043] Figure 7 This is a waveform diagram of the frequency domain and time domain separation of the synthetic signal of 8-channel ultrasonic sensors with the same amplitude and random defect positions in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments. It should be noted that the present invention can also be applied through other equivalent embodiments. The embodiments and the accompanying drawings provided in the following embodiments are merely examples to illustrate the basic technical concept of the present invention. Parameters such as the model, number, shape, and size of the relevant components in the embodiments may be changed in a specific implementation environment.

[0045] Figure 1 The present invention includes the following:

[0046] Signal synthesis:

[0047] S1) Obtain the echo signal u detected by each ultrasonic sensor n (t), preprocess the echo signal to obtain the envelope signal x n (t);

[0048] S2) A discrete sequence g is generated by a digital device n (n), the discrete sequence is reshaped into a carrier signal g n (t);

[0049] S3) convert the N-channel ultrasonic sensor envelope signal x n (t) Carrier signal g with different frequencies from N groups n (t) Modulate through the modulation circuit to generate N modulated signals y with different frequencies but the same phase as the original signal n (t);

[0050] S4) The modulated N-channel ultrasonic sensor signal y n (t) Add through the adding circuit to synthesize a signal y∑ (t);

[0051] S5) synthesize the signal y from the N ultrasonic sensors ∑ (t), the signal discrete digital sequence y is obtained through analog-to-digital conversion ∑ (k);

[0052] Signal separation:

[0053] In the host computer, the discrete sequence y of the digitized synthetic signal is ∑ (k) Perform wavelet packet decomposition and reconstruction to obtain each separated signal from The echo signal parameters of the ultrasonic sensor are estimated.

[0054] As a preferred embodiment of the present invention, in the above step S1), N ultrasonic sensors are used to perform ultrasonic testing on the material to be tested, and the echo signal u of each ultrasonic sensor is obtained. n (t),

[0055] u n (t) = h n (tt n )cos(2πf0(tt n )), n = 1, 2, ... N

[0056] Among them, h n (t) is the envelope of each ultrasonic echo signal, f0 is the center frequency of the ultrasonic sensor, t n is the echo arrival time.

[0057] As a preferred embodiment of the present invention, in the above step S1), each ultrasonic sensor element echo signal u n (t) Perform noise reduction and envelope preprocessing to obtain the processed envelope signal x n (t),

[0058]

[0059] Among them, β n is the amplitude, α n is the form factor, t n is the echo arrival time.

[0060] As a preferred embodiment of the present invention, in the above step S2), the digital device CPU or FPGA generates a discrete sequence g n (n), generate different frequencies f through D / A shaping circuit n The carrier signal g n (t),

[0061]

[0062] Among them, A n is the carrier signal amplitude, is the initial phase of the carrier signal.

[0063] As a preferred embodiment of the present invention, in the above step S3), the envelope signal x n (t) and the carrier signal g n (t) Modulate the signal through the multiplication circuit to generate the modulated frequency shift signal y n (t),

[0064]

[0065] Among them, A n is the carrier signal amplitude, β n is the envelope signal amplitude, α n is the form factor, t n is the echo arrival time, f n is the frequency of the carrier signal, is the initial phase of the carrier signal.

[0066] As a preferred embodiment of the present invention, in the above step S4), the N frequency-shifted signals y n (t) Through the adding circuit, synthesize a signal y ∑ (t),

[0067]

[0068] As a preferred embodiment of the present invention, in the above step S5), the synthesized signal y ∑ (t) Perform A / D conversion to obtain the discrete digital sequence y of the synthetic signal ∑ (k), k = 0, 1, 2, ..., L-1, where L is the length of the sampled data, and the discrete digital sequence y ∑ (k) Transmit to the host computer.

[0069] As a preferred embodiment of the present invention, in the above step S4), the first carrier frequency is the base frequency f1, and the maximum allowable bandwidth of the composite signal is B, then

[0070]

[0071] The remaining carrier frequencies are Sure;

[0072] The carrier frequency is f n The cosine signal of each channel is modulated, and the ultrasonic frequency bands in the synthetic signal overlap.

[0073] As a preferred embodiment of the present invention, the above-mentioned synthetic signal discrete sequence y ∑(k) Reconstruction includes: converting the synthetic sequence y ∑ (k) Decompose into N sub-bands, arrange the sub-bands from low to high according to frequency, and obtain the separated channel signal sequences in sequence from The time delay and amplitude of the echo signal are obtained.

[0074] like Figure 2 The waveforms of the ultrasonic sensor echo signal in the time domain and frequency domain are shown as the preferred embodiment of the present invention. The initial wave amplitude β1=1, t1=3×10 -6 , echo amplitude β2=0.2, t2=9×10 -6 The center frequency of the signal is 5MHz, and the sampling frequency is set to f0=2×10 7 , Figure 2 (a) is the time domain waveform of the signal, Figure 2 (b) is the frequency domain waveform of the signal.

[0075] Figure 3 This is a time-frequency diagram of the synthetic signal of 8 ultrasonic sensors in a preferred embodiment of the present invention.

[0076] Figure 4 The time domain and frequency domain diagrams of the synthesized signals of 8 ultrasonic sensors with the same amplitude and the same defect position in the preferred embodiment of the present invention are as follows: 8 ultrasonic sensor signals with the same amplitude and the same defect position are taken, and the 8 ultrasonic sensor signals with the same amplitude and the same defect position are modulated with 8 cosine signals respectively. The frequencies of the 8 modulated signals are f1 = 0.625MHz, f2 = 1.875MHz, f3 = 3.125MHz, f4 = 4.375MHz, f5 = 5.625MHz, f6 = 6.875MHz, f7 = 8.125MHz, and f8 = 9.375MHz. The 8-channel modulated signals are synthesized, and it can be seen that the 8 signals have no gaps in the frequency domain and are aliased. Figure 4 (a) is the time domain waveform of the 8-channel modulation signal. Figure 4 (b) is the frequency domain waveform of the 8-channel modulated signal.

[0077] Figure 5 This is a frequency domain and time domain separation waveform diagram of 8-way ultrasonic sensor synthetic signal with the same amplitude and the same defect location in the preferred embodiment of the present invention. The 8-way synthetic signal is decomposed and reconstructed by 3-layer wavelet packet using Meyer wavelet to obtain the parameters and waveforms of the 8-way separation signal. Figure 5 (a) is the channel 1 signal with a carrier frequency of 0.625 MHz, and the echo amplitude after taking the envelope Figure 5 (b) is the channel 2 signal with a carrier frequency of 1.875MHz, and the echo amplitude after taking the envelope Figure 5(c) is the channel 3 signal with a carrier frequency of 3.125MHz, and the echo amplitude after taking the envelope Figure 5 (d) is the channel 4 signal with a carrier frequency of 4.375MHz, and the echo amplitude after taking the envelope Figure 5 (e) is the channel 5 signal with a carrier frequency of 5.625MHz, and the echo amplitude after taking the envelope Figure 5 (f) is the channel 6 signal with a carrier frequency of 6.875MHz, and the echo amplitude after taking the envelope Figure 5 (g) is the channel 7 signal with a carrier frequency of 8.125MHz, and the echo amplitude after taking the envelope Figure 5 (h) is the channel 8 signal with a carrier frequency of 9.375MHz, and the echo amplitude after taking the envelope

[0078] The errors of the 8-way separated signals are shown in Table 1.

[0079] Table 1 Error of separated signals

[0080]

[0081] Figure 6 In the preferred embodiment of the present invention, the time domain diagram and frequency domain diagram of the synthesized signal of 8 ultrasonic sensors with the same amplitude and random defect positions are taken. The 8 channels have the same amplitude. Under the premise of ensuring that the echo signal does not overlap with the initial wave, the echo signal time is randomly assigned to obtain 8 channels of ultrasonic sensor signals with the same amplitude and random defect positions. The 8 channels of ultrasonic sensor signals with the same amplitude and random defect positions are modulated with 8 channels of cosine signals respectively. The frequencies of the 8 channels of modulated signals are f1=0.625MHz, f2=1.875MHz, f3=3.125MHz, f4=4.375MHz, f5=5.625MHz, f6=6.875MHz, f7=8.125MHz, and f8=9.375MHz. The 8-channel modulated signals are synthesized, and it can be seen that the 8 channels of signals have aliasing in the time domain, no interval in the frequency domain, and aliasing. Figure 6 (a) is the time domain waveform of the 8-channel modulation signal. Figure 6 (b) is the frequency domain waveform of the 8-channel modulated signal.

[0082] Figure 7 The frequency domain and time domain separation waveforms of the 8-way ultrasonic sensor synthetic signal with the same amplitude and random defect position in the preferred embodiment of the present invention are shown. The 8-way synthetic signal is decomposed and reconstructed by 3-layer wavelet packet using Meyer wavelet to obtain the parameters and waveforms of the 8-way separation signal. Figure 7(a) is the channel 1 signal with a carrier frequency of 0.625 MHz, and the echo amplitude after taking the envelope Figure 7 (b) is the channel 2 signal with a carrier frequency of 1.875MHz, and the echo amplitude after taking the envelope Figure 7 (c) is the channel 3 signal with a carrier frequency of 3.125MHz, and the echo amplitude after taking the envelope Figure 7 (d) is the channel 4 signal with a carrier frequency of 4.375MHz, and the echo amplitude after taking the envelope Figure 7 (e) is the channel 5 signal with a carrier frequency of 5.625MHz, and the echo amplitude after taking the envelope Figure 7 (f) is the channel 6 signal with a carrier frequency of 6.875MHz, and the echo amplitude after taking the envelope Figure 7 (g) is the channel 7 signal with a carrier frequency of 8.125MHz, and the echo amplitude after taking the envelope Figure 7 (h) is the channel 8 signal with a carrier frequency of 9.375MHz, and the echo amplitude after taking the envelope

[0083] The errors of the 8-way separated signals are shown in Table 2.

[0084] Table 2 Error of separated signals

[0085]

[0086]

[0087] The description in the examples is only for the specific demonstration of the feasibility of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent implementation or modification that does not depart from the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for synthesizing and separating ultrasonic signals, characterized in that: Includes the following: Signal synthesis: S1) Obtain the echo signal u detected by each ultrasonic sensor n (t), preprocess the echo signal to obtain the envelope signal x n (t); S2) A discrete sequence g is generated by a digital device n (n), the discrete sequence is reshaped into a carrier signal g n (t); S3) convert the N-channel ultrasonic sensor envelope signal x n (t) Carrier signal g with different frequencies from N groups n (t) Modulate through the modulation circuit to generate N modulated signals y with different frequencies but the same phase as the original signal n (t); In step S3), the envelope signal x n (t) and the carrier signal g n (t) Modulate the signal through the multiplication circuit to generate the modulated frequency shift signal y n (t), Among them, A n is the carrier signal amplitude, β n is the envelope signal amplitude, α n is the form factor, t n is the echo arrival time, f n is the frequency of the carrier signal, is the initial phase of the carrier signal; S4) The modulated N-channel ultrasonic sensor signal y n (t) Add through the adding circuit to synthesize a signal y ∑ (t); S5) synthesize the signal y from the N ultrasonic sensors ∑ (t) Obtain the synthetic signal discrete digital sequence y through analog-to-digital conversion ∑ (k); Signal separation: In the host computer, the discrete sequence y of the digitized synthetic signal is ∑ (k) Perform wavelet packet decomposition and reconstruction to obtain each separated signal from The echo signal parameters are estimated.

2. The ultrasonic signal synthesis and separation method according to claim 1, wherein: In step S1), N ultrasonic sensors are used to perform ultrasonic testing on the material to be tested, and an echo signal u of each ultrasonic sensor is obtained. n (t), u n (t)=h n (t-t n )cos(2πf0(t-t n )),n=1,2,…N Among them, h n (t) is the envelope of each ultrasonic echo signal, f0 is the center frequency of the ultrasonic sensor, t n is the echo arrival time.

3. The ultrasonic signal synthesis and separation method according to claim 1, wherein: In step S1), each ultrasonic sensor element echo signal u n (t) Perform noise reduction and envelope preprocessing to obtain the processed envelope signal x n (t), Among them, β n is the amplitude, α n is the form factor, t n is the echo arrival time.

4. The ultrasonic signal synthesis and separation method according to claim 1, wherein: In step S2), the digital device CPU or FPGA generates a discrete sequence g n (n), generate different frequencies f through D / A shaping circuit n The carrier signal g n (t), Among them, A n is the carrier signal amplitude, is the initial phase of the carrier signal.

5. The ultrasonic signal synthesis and separation method according to claim 1, wherein: In step S4), the N frequency-shifted signals y n (t) Through the adding circuit, synthesize a signal y ∑ (t), 6. The ultrasonic signal synthesis and separation method according to claim 1, wherein: In step S5), the synthesized signal y ∑ (t) Perform A / D conversion to obtain the discrete digital sequence y of the synthetic signal ∑ (k), k=0,1,2,…,L-1, where L is the length of the sampled data, and the discrete digital sequence y ∑ (k) Transmit to the host computer.

7. The ultrasonic signal synthesis and separation method according to claim 1, wherein: In step S4), the first carrier frequency is the base frequency f1, and the maximum allowable bandwidth of the composite signal is B. The remaining carrier frequencies are Sure; The carrier frequency is f n The cosine signal of each channel is modulated, and the ultrasonic frequency bands in the synthetic signal overlap.

8. The ultrasonic signal synthesis and separation method according to claim 1, wherein: The synthetic signal discrete sequence y ∑ (k) Reconstruction includes: converting the synthetic sequence y ∑ (k) Decompose into N sub-bands, arrange the sub-bands from low to high according to frequency, and obtain the separated channel signal sequences in sequence from The time delay and amplitude of the echo signal are obtained.

Images