Orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method
By employing orthogonal digital phase-sensitive detection and sliding integral methods, the instability problem of extracting the amplitude and phase of time-frequency electromagnetic signals in noisy environments is solved, enabling stable extraction of the complex response of the target frequency in a digital signal processing system, thereby enhancing the system's noise immunity and networking flexibility.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-04-03
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies struggle to reliably extract amplitude and phase information of time-frequency electromagnetic signals in complex noise environments. In particular, traditional phase-sensitive detection methods are susceptible to noise interference in digital signal processing systems.
An orthogonal digital phase-sensitive detection method is adopted. By generating in-phase and quadrature reference signals, performing multiplication operations, and then performing sliding integration, a complex response is constructed to extract amplitude and phase information.
It achieves stable extraction of the complex response amplitude and phase of the target frequency in a noisy environment, improves the stability and consistency of the extraction, and enhances the networking flexibility of the array-type TFEM system.
Smart Images
Figure CN122151236A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of geophysical electromagnetic exploration data processing technology, and in particular to a method for extracting time-frequency electromagnetic complex responses using orthogonal digital phase-sensitive detection. Background Technology
[0002] Time-frequency electromagnetic detection (TFD) technology is an important geophysical exploration method. It involves transmitting electromagnetic fields of a specific frequency at the Earth's surface or underground and measuring the electromagnetic response signal at the receiving end to obtain information about the electrical structure of the subsurface medium. In practical applications, the receiving system typically samples the entire waveform of the electromagnetic response signal and extracts the amplitude and phase information at the target frequency through subsequent signal processing, thereby obtaining the complex response characteristics of the subsurface medium to the electromagnetic field. However, in actual measurement environments, the received signal often contains multiple interference components, such as low-frequency drift, power frequency interference, environmental electromagnetic noise, and other asynchronous signals. These interferences significantly reduce the signal-to-noise ratio of the target frequency signal, making the extraction of complex response parameters difficult.
[0003] In existing technologies, a common approach is to perform a Fast Fourier Transform (FFT) on the sampled signal and obtain the amplitude and phase information of the target frequency through spectral analysis. This method achieves good results when the signal is stable and the signal-to-noise ratio is high. However, in the presence of strong noise or when the signal amplitude and phase change slowly, the spectral estimation results are easily affected by interference, thus reducing the stability of the complex response extraction. Another approach uses phase-locked loop (PLL) or phase-sensitive detection techniques, which extract the target frequency component by performing correlation operations between the received signal and a reference signal. These methods have been applied in analog circuit implementations, but in digital signal processing systems, directly using traditional phase-sensitive detection structures may still be affected by noise interference or improper parameter settings, leading to unstable extraction results.
[0004] Therefore, in the processing of time-frequency electromagnetic full waveform sampling data, how to stably extract the amplitude and phase information of the target frequency signal under complex noise environment remains a technical problem that needs to be solved. Summary of the Invention
[0005] The purpose of this invention is to solve the problem that existing technologies often fail to stably obtain the amplitude and phase information of the target frequency components when directly using spectrum analysis or conventional filtering methods to receive signals.
[0006] To achieve the above objectives, this invention provides a method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection, comprising the following steps: S1. Acquire Received Signal: Read the data file from the time-frequency electromagnetic instrument receiver; S2. Generate quadrature reference signals: Construct in-phase and quadrature reference signals based on the target frequency; S3, In-phase digital phase-sensitive detection: Multiply the received signal with the in-phase reference signal to obtain the in-phase multiplication output sequence; S4. Orthogonal digital phase-sensitive detection: Multiply the received signal with the orthogonal reference signal to obtain the orthogonal multiplication output sequence; S5. Coherent Integral: Sets a sliding integration window to calculate in-phase and quadrature components; S6. Calculate the complex response: Construct the complex response and calculate the amplitude and phase of the complex response.
[0007] Furthermore, step S1 specifically includes: Read the data file from the time-frequency electromagnetic instrument receiver to obtain the discrete sequence: ; in, For the first The received signal at each sampling point This represents the total number of sampling points; The sampling time is: ; in, The sampling interval; The sampling rate is: .
[0008] Furthermore, step S2 specifically includes: According to the target frequency Construct two orthogonal reference signals: ; ; in, For in-phase reference signal, This is an orthogonal reference signal.
[0009] Furthermore, step S3 specifically includes: Multiply the received signal by the in-phase reference signal: ; in, This is the output sequence for the in-phase multiplication method.
[0010] Furthermore, step S4 specifically includes: Multiply the received signal by the quadrature reference signal: ; in, This is the output sequence for orthogonal multiplication.
[0011] Furthermore, step S5 specifically includes: Suppose that the sliding integral window contains a set of sample points. The number of sample points in the window is ; Calculate the in-phase components: ; in, For the first The in-phase components of a time window; Calculate orthogonal components: ; in, For the first The orthogonal components of a time window.
[0012] Furthermore, step S6 specifically includes: Constructing complex responses: ; in, The imaginary unit; The complex response amplitude is: ; The complex response phase is: ; in, It is the arctangent function in the four quadrants; The amplitude and phase are the target frequency complex response.
[0013] The present invention employs the above-mentioned orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method, and its beneficial effects are as follows: (1) The present invention has strong anti-noise performance. Through orthogonal digital phase-sensitive detection and coherent integration, only the synchronous component with the same frequency as the reference signal is retained, and the other asynchronous interference is effectively suppressed during the integration process. (2) The complex response extraction of the present invention is stable and can simultaneously obtain the amplitude and phase information of the target frequency component, thereby improving the stability and consistency of complex response parameter extraction; (3) The present invention can be directly applied to the full waveform sampling data of the receiver, and supports the post-processing of multi-channel / multi-node data on the computer; there is no need to transmit the transmitter current waveform to the receiver in real time to realize hardware phase-sensitive detection, which enhances the networking flexibility of the array-type TFEM system. Attached Figure Description
[0014] Figure 1 This is a flowchart of an orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method according to an embodiment of the present invention; Figure 2This is a time-domain waveform diagram of the received signal (including harmonics and noise) and the true fundamental frequency of an orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method according to an embodiment of the present invention; Figure 3 This is a time-domain waveform diagram of the orthogonal reference signal in an orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method according to an embodiment of the present invention; Figure 4 This is a time-domain waveform diagram of the phase-sensitive multiplication output of an orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method according to an embodiment of the present invention; Figure 5 This is a time-domain waveform diagram of the coherent integral output of an orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method according to an embodiment of the present invention; Figure 6 This is a time-domain waveform diagram of the amplitude extraction result of an orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method according to an embodiment of the present invention; Figure 7 This is a time-domain waveform diagram of the phase extraction result of an orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method according to an embodiment of the present invention; Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.
[0016] like Figure 1 As shown in the figure, this invention provides a method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection. The data used is the actual measured full waveform sampling data of the receiver, or it can be the simulation data used for algorithm verification. The two are equivalent in the processing link.
[0017] In this embodiment, the sampling rate is set to ; Target frequency is ; Sampling time is ; Therefore, the number of sampling points is ; For ease of demonstration, the following... Figure 2 , Figure 3 , Figure 4 Only the time-domain waveform segments of the first 5 cycles are displayed.
[0018] S1. The sampling sequence of a certain channel of the receiver is denoted as: ; in, For the first The received signal at each sampling point This represents the total number of sampling points; Received signal It typically includes the target frequency response as well as strong noise such as low-frequency drift, power frequency interference, random noise, and transient pulses. The true fundamental frequency component is submerged by noise (e.g., Figure 2 (As shown). Figure 2 In the diagram, the solid blue line represents the original received signal containing the fundamental frequency signal, harmonic signals, and strong noise components, while the dashed red line represents the fundamental frequency signal at 1 Hz. Subsequent orthogonal digital phase-sensitive detection extracts the amplitude and phase of the true fundamental frequency from the original received signal.
[0019] S2. In this embodiment, the target frequency Sampling time interval Sampling time is ; Construct two orthogonal reference signals (e.g.) Figure 3 (as shown); Figure 3 In the middle, the solid blue line The in-phase reference signal is represented by the red dashed line. This is an orthogonal reference signal.
[0020] S3, receive signal With two orthogonal reference signals respectively , Multiplying them, we achieve in-phase digital phase-sensitive detection (DPSDI) and quadrature digital phase-sensitive detection (DPSDQ) respectively, to obtain the following: Figure 4 The results are shown. Figure 4 In the middle, the solid blue line For phase-sensitive detection of in-phase output, the red dashed line represents... This is for phase-sensitive detection with orthogonal output. The same method can be used to obtain... Figure 2 The true fundamental frequency is shown in both in-phase and quadrature outputs.
[0021] S4. In order to suppress noise and asynchronous interference, Figure 4 The phase-sensitive multiplication output shown is processed by sliding coherent integration (DLPF).
[0022] Let the integration window contain One signal cycle, take Then the integration window length is: ; The sliding coherent integral accumulates and enhances the target frequency component synchronized with the reference signal, while simultaneously canceling out various noises during the integration process, thus obtaining the target frequency in the received signal. The complex response in-phase component I and quadrature component Q (e.g.) Figure 5 (As shown).
[0023] S5. Construct a complex response from the in-phase component I and the quadrature component Q, and extract the amplitude of the target frequency signal. and phase information This is the final result of orthogonal digital phase-sensitive detection, the ODPSD amplitude (e.g. Figure 6 (as shown) and ODPSD phase (as shown) Figure 7 (As shown).
[0024] To verify the processing accuracy, Figure 1 By performing the same orthogonal digital phase-sensitive detection on the "true fundamental frequency" signal, the "true amplitude" (e.g.) can be obtained. Figure 6 (as shown) and "truth phase" (such as) Figure 7 (As shown). Figure 6 The ODPSD amplitude, indicated by the red circle, largely coincides with the true amplitude, indicated by the blue solid line. Figure 7 The ODPSD phase, indicated by the red circle, is almost identical to the true phase, indicated by the blue solid line, effectively suppressing the received signal. Various noises.
[0025] The results show that the processing link based on orthogonal digital phase-sensitive detection and coherent integration can stably extract the complex response amplitude and phase at the target frequency, and can be used for post-processing of full waveform sampling data of array-type TFEM receivers.
[0026] Therefore, the present invention adopts the above-mentioned orthogonal digital phase-sensitive detection time-frequency electromagnetic complex response extraction method, which has the following advantages: 1) Strong noise resistance: Through orthogonal digital phase-sensitive detection and coherent integration, only the synchronous component with the same frequency as the reference signal is retained, and other asynchronous interferences are effectively suppressed during the integration process; 2) Stable complex response extraction: The amplitude and phase information of the target frequency component can be obtained simultaneously, improving the stability and consistency of complex response parameter extraction; 3) It can be directly applied to the full waveform sampling data of the receiver, supporting post-processing of multi-channel / multi-node data on the computer; there is no need to transmit the transmitter current waveform to the receiver in real time to realize hardware phase-sensitive detection, enhancing the networking flexibility of the array-type TFEM system.
[0027] It is worth noting that all contents not described in detail in this invention are existing technologies and are well known to those skilled in the art.
[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection, characterized in that, Includes the following steps: S1. Acquire Received Signal: Read the data file from the time-frequency electromagnetic instrument receiver; S2. Generate quadrature reference signals: Construct in-phase and quadrature reference signals based on the target frequency; S3, Digital Phase Sensitive Detection (DPSDI): Multiply the received signal with the in-phase reference signal to obtain the in-phase multiplication output sequence; S4, Orthogonal Digital Phase Sensitive Detection (DPSDQ): Multiply the received signal with the orthogonal reference signal to obtain the orthogonal multiplication output sequence; S5, Coherent Integral DLPF: Sets the sliding integration window to calculate in-phase and quadrature components; S6. Calculate the complex response: Construct the complex response and calculate the amplitude and phase of the complex response.
2. The method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection according to claim 1, characterized in that, Step S1 specifically involves: Read the data file from the time-frequency electromagnetic instrument receiver to obtain the discrete sequence: ； in, For the first The received signal at each sampling point This represents the total number of sampling points; The sampling time is: ； in, The sampling interval; The sampling rate is: 。 3. The method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection according to claim 2, characterized in that, Step S2 specifically involves: According to the target frequency Construct two orthogonal reference signals: ； ； in, For in-phase reference signal, This is an orthogonal reference signal.
4. The method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection according to claim 3, characterized in that, Step S3 specifically involves: Multiply the received signal by the in-phase reference signal: ； in, This is the output sequence for the in-phase multiplication method.
5. The method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection according to claim 4, characterized in that, Step S4 specifically involves: Multiply the received signal by the quadrature reference signal: ； in, This is the output sequence for orthogonal multiplication.
6. The method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection according to claim 5, characterized in that, Step S5 specifically involves: Suppose that the sliding integral window contains a set of sample points. The number of sample points in the window is ; Calculate the in-phase components: ； in, For the first The in-phase components of a time window; Calculate orthogonal components: ； in, For the first The orthogonal components of a time window.
7. The method for extracting the time-frequency electromagnetic complex response of orthogonal digital phase-sensitive detection according to claim 6, characterized in that, Step S6 specifically involves: Constructing complex responses: ； in, The imaginary unit; The complex response amplitude is: ； The complex response phase is: ； in, It is the arctangent function in the four quadrants; The amplitude and phase are the target frequency complex response.