An ultra-high-precision underground cavity structure detection system, method and related equipment

Abstract

The present application discloses an ultra-high-precision underground cavity structure detection system, method and related equipment, which relate to the field of microwave photon technology. The system includes: an above-ground transmitting module, which is used to generate an optical sideband signal and divide the optical sideband signal into a transmitted optical signal and a local oscillator optical signal through a branching operation; an underground transmitting module, which is used to convert the transmitted optical signal into an electrical signal through a beat frequency, and amplify the electrical signal to obtain an amplified electrical signal, which is transmitted through an antenna; an underground receiving module, which is used to obtain an electromagnetic wave signal, amplify the electromagnetic wave signal and modulate it to a local oscillator optical signal to obtain a modulated signal, which is obtained by reflecting the amplified electrical signal from the target; and an above-ground receiving module, which is used to perform de-skewing receiving processing, filtering processing and signal processing on the modulated signal to obtain a target signal.

Description

Technical Field

[0001] The present application relates to the field of microwave photon technology, and in particular to an ultra-high precision underground cavity structure detection system, method and related equipment. Background Art

[0002] Currently, accurate understanding of the internal structure of underground cavities is crucial for high-quality geological exploration, engineering inspections, archaeological excavations, and other activities. Cavity detection radars transmit signals via waveguides, emit high-frequency electromagnetic waves via antennas, and receive reflected signals to analyze the structure, properties, and location of the underground medium. Radar range resolution is inversely proportional to signal bandwidth; a larger signal bandwidth yields better range resolution and more accurate cavity detection.

[0003] However, most existing ground-penetrating radars use antennas to transmit and receive high-frequency electromagnetic waves to detect the internal properties and distribution patterns of materials in a medium. By studying changes in the polarization of radar waves, information related to the physical properties of the subsurface medium can be obtained. However, existing ground-penetrating radars lack the capability to measure underground cavity structures. Existing radars capable of detecting underground cavity structures often generate signals using an electronics-based method that up-converts the signal generated by a reference source. This method is relatively simple and stable, but generating wide-bandwidth signals is a challenge that electronics cannot address. Therefore, the signal bandwidth of existing underground cavity detection radars is generally below 1 GHz. For applications requiring precise detection, the corresponding range resolution is far from sufficient. Furthermore, existing underground cavity detection radars transmit signals through waveguides, a structure that limits their scalability and prevents flexible adjustment for achieving optimal detection results in complex terrain. Furthermore, processing broadband signals requires enormous amounts of data, placing high demands on signal processing. Currently, no suitable method exists to address these issues. Therefore, it is necessary to develop an ultra-high-precision underground cavity detection system to at least partially address these issues. Summary of the Invention

[0004] The Summary of the Invention introduces a series of simplified concepts that will be further described in the Detailed Description of the Invention. The Summary of the Invention of this application is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] In a first aspect, an embodiment of the present application provides an ultra-high precision underground cavity structure detection system, the system comprising:

[0006] A ground transmitting module, the ground transmitting module is used to generate an optical sideband signal and split the optical sideband signal into a transmitting optical signal and a local oscillator optical signal through a branching operation;

[0007] An underground transmitting module, configured to convert the transmitted optical signal into an electrical signal by beat frequency conversion, amplify the electrical signal to obtain an amplified electrical signal, and transmit the amplified electrical signal through an antenna;

[0008] an underground receiving module, the underground receiving module being used to acquire an electromagnetic wave signal, amplify the electromagnetic wave signal, and modulate the electromagnetic wave signal onto the local oscillation optical signal to obtain a modulated signal, the electromagnetic wave signal being obtained by reflecting the amplified electrical signal from a target;

[0009] The ground receiving module is used to perform de-skewing receiving processing, filtering processing and signal processing on the modulated signal to obtain a target signal.

[0010] In one embodiment of the present invention, the ground transmitting module includes: a single-frequency laser, a reference source, a first electro-optical modulator, an optical combining filter and an optical coupler;

[0011] The single-frequency laser is used to generate an optical carrier;

[0012] The reference source is used to generate a linear frequency modulation signal;

[0013] The first electro-optical modulator is used to modulate the linear frequency modulation signal onto the optical carrier, adjust the bias voltage to a carrier suppression state, and adjust the amplitude of the linear frequency modulation signal to obtain an initial optical signal;

[0014] The optical combination filter is used to filter the initial optical signal to obtain an optical sideband signal;

[0015] The optical coupler is used to divide the optical sideband signal into a transmission optical signal and a local oscillator optical signal through a branching operation.

[0016] In one embodiment of the present invention, the underground transmission module includes: a first photodetector and a low noise amplifier;

[0017] The first photodetector is used to perform beat frequency processing on the emitted light signal to obtain an electrical signal;

[0018] The low noise amplifier is used to amplify the electrical signal to obtain an amplified electrical signal.

[0019] In one embodiment of the present invention, the underground receiving module includes: an electrical amplifier group and a second electro-optical modulator;

[0020] The electric amplifier group is used to amplify the electromagnetic wave signal to obtain an amplified electromagnetic wave signal;

[0021] The second electro-optical modulator is used to modulate the amplified electromagnetic wave signal into the local oscillation optical signal to obtain a modulated signal.

[0022] In one embodiment of the present invention, the ground receiving module includes: an adjustable optical delay line, a second photodetector, an intermediate frequency filter, and a digital signal processor;

[0023] The adjustable optical delay line is used to perform a time delay operation on the local oscillator optical signal;

[0024] The second photodetector is used to perform de-skewing reception processing on the modulated signal to obtain an intermediate frequency electrical signal;

[0025] The intermediate frequency filter is used to filter the intermediate frequency electrical signal to obtain a filtered electrical signal;

[0026] The digital signal processor is used to perform signal processing on the filtered electrical signal to obtain a target signal.

[0027] In one embodiment of the present invention, the initial optical signal is expressed as:

[0028]

[0029] Among them, E l is the amplitude of the light wave from the laser, ω l is the angular frequency of the light wave from the laser, ω0 is the center frequency of the IF signal from the DDS, K0 is the chirp rate of the IF signal from the DDS, T is the time period of the IF signal from the direct digital frequency synthesizer, J 2n-1 (β1) is the first type (2n-1) nd Bessel function, β1 is the modulation index of the first electro-optic modulator, and t is time.

[0030] In one embodiment of the present invention, the modulated signal is expressed as:

[0031]

[0032] where Δφ represents the phase difference between the two arms of the second electro-optic modulator, V π2 is the half-wave voltage of the second EO modulator, V eco (t) represents the electromagnetic wave signal received by the receiving antenna, E l' (t) is the delayed optical signal.

[0033] In a second aspect, the present application proposes an ultra-high precision underground cavity structure detection method, the method comprising:

[0034] Acquire optical sideband signal;

[0035] Splitting the optical sideband signal into a transmitted optical signal and a local oscillator optical signal through a branching operation;

[0036] Converting the emitted light signal into an electrical signal by beat frequency, and amplifying the electrical signal to obtain an amplified electrical signal;

[0037] The amplified electrical signal is transmitted through an antenna, and a layer-by-layer scanning method is used for detection, and the transmitted electromagnetic wave signal is received by a receiving antenna;

[0038] amplifying the electromagnetic wave signal and modulating it into the local oscillator light signal to obtain a modulated signal;

[0039] The modulated signal is subjected to de-skewing receiving processing, filtering processing and signal processing to obtain a target signal.

[0040] In the third aspect, an electronic device includes: a memory, a processor, and a computer program stored in the above-mentioned memory and capable of running on the above-mentioned processor, wherein the above-mentioned processor is used to implement the steps of an ultra-high precision underground cavity structure detection method as described in the second aspect above when executing the computer program stored in the memory.

[0041] In a fourth aspect, the present application further proposes a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of an ultra-high-precision underground cavity structure detection method of the second aspect are implemented.

[0042] In summary, an ultra-high precision underground cavity structure detection system according to an embodiment of the present application includes: an above-ground transmitting module, the above-ground transmitting module is used to generate an optical sideband signal, and divide the optical sideband signal into a transmitted optical signal and a local oscillator optical signal through a branching operation; an underground transmitting module, the underground transmitting module is used to convert the transmitted optical signal into an electrical signal through a beat frequency, and amplify the electrical signal to obtain an amplified electrical signal, and the amplified electrical signal is transmitted through an antenna; an underground receiving module, the underground receiving module is used to obtain an electromagnetic wave signal, amplify the electromagnetic wave signal and modulate it to the local oscillator optical signal to obtain a modulated signal, and the electromagnetic wave signal is obtained after the amplified electrical signal is reflected by the target; an above-ground receiving module, the above-ground receiving module is used to perform de-skewing reception processing, filtering processing and signal processing on the modulated signal to obtain a target signal. By processing the electromagnetic wave signal with de-skewing reception technology, the amount of data processing is reduced, and the problem of the radar having a close-range blind spot is also solved by setting the delay of an adjustable optical delay line. The present application effectively combines the advantages of broadband signal generation of microwave photonic technology, flexible extension of optical fiber transmission signals and microwave photonic de-skewing reception technology.

[0043] The ultra-high precision underground cavity structure detection system proposed in this application, and other advantages, objectives and features of this application will be reflected in part through the following description, and in part will also be understood by technical personnel in this field through research and practice of this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present description. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0045] Figure 1 A schematic diagram of the structure of an ultra-high precision underground cavity structure detection system provided in an embodiment of the present application;

[0046] Figure 2 This is a spectrum output after passing through an optical combination filter in an ultra-high-precision underground cavity structure detection system provided in an embodiment of the present application;

[0047] Figure 3 This is a spectrum diagram of the LFM signal generated in an ultra-high-precision underground cavity structure detection system provided in an embodiment of the present application;

[0048] Figure 4 A schematic diagram of a microwave photon de-skewing receiving technology in an ultra-high-precision underground cavity structure detection system provided in an embodiment of the present application;

[0049] Figure 5 This is a resolution test result diagram obtained by de-skewing the single-cycle echo signals of two adjacent targets in an ultra-high-precision underground cavity structure detection system provided in an embodiment of the present application;

[0050] Figure 6 A schematic diagram of the process of an ultra-high precision underground cavity structure detection method provided in an embodiment of the present application;

[0051] Figure 7 A schematic diagram of the structure of an ultra-high precision underground cavity structure detection electronic device provided in an embodiment of the present application.

[0052] in, Figure 1The correspondence between the reference numerals and the component names is: 101 ground transmitting module, 1011 single-frequency laser, 1012 reference source, 1013 first electro-optical modulator, 1014 optical combination filter, 1015 optical coupler, 201 underground transmitting module, 2011 first photodetector, 2012 low-noise amplifier, 301 underground receiving module, 3011 electric amplifier group, 3012 second electro-optical modulator, 401 ground receiving module, 4011 adjustable optical delay line, 4012 second photodetector, 4013 intermediate frequency filter, 4014 digital signal processor. DETAILED DESCRIPTION

[0053] In order to better understand the technical solutions provided by the embodiments of this specification, the technical solutions of the embodiments of this specification are described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of this specification and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this specification, rather than limitations on the technical solutions of this specification. In the absence of conflict, the embodiments of this specification and the technical features in the embodiments can be combined with each other.

[0054] In this article, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also include elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the statement "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or equipment comprising the elements. The term "two or more" includes two or more than two cases.

[0055] See also Figure 1 , which is a schematic diagram of the structure of an ultra-high-precision underground cavity structure detection system provided in an embodiment of the present application, which may specifically include:

[0056] A ground transmitting module 101, which is used to generate an optical sideband signal and split the optical sideband signal into a transmitting optical signal and a local oscillator optical signal through a branching operation;

[0057] An underground transmitting module 201 is configured to convert the transmitted optical signal into an electrical signal by using a beat frequency method, and amplify the electrical signal to obtain an amplified electrical signal, which is then transmitted via an antenna;

[0058] An underground receiving module 301 is used to obtain an electromagnetic wave signal, amplify the electromagnetic wave signal, and modulate it into the local oscillation optical signal to obtain a modulated signal. The electromagnetic wave signal is obtained by reflecting the amplified electrical signal from the target.

[0059] The ground receiving module 401 is used to perform de-skewing, filtering and signal processing on the modulated signal to obtain a target signal.

[0060] For example, the ground transmitter module 101 generates an optical sideband signal. This optical sideband signal may be an optical signal with specific frequency characteristics. This optical sideband signal is then split into two parts through a branching operation: a transmitted optical signal and a local oscillator optical signal. The transmitted optical signal is converted into an electrical signal and transmitted for target detection, while the local oscillator optical signal is used in subsequent processing.

[0061] The underground transmission module 201 receives the optical transmission signal from the aboveground transmission module 101. It converts the optical transmission signal into an electrical signal through beat frequency conversion. The resulting electrical signal is amplified to obtain an amplified electrical signal, which is then transmitted to enhance signal strength and detectability.

[0062] The underground receiving module 301 is responsible for acquiring an electromagnetic wave signal. This electromagnetic wave signal is generated by reflecting the amplified electrical signal off a target. Reflection of the amplified electrical signal by the target generates a new electromagnetic wave signal. After receiving this signal, the underground receiving module 301 amplifies the acquired electromagnetic wave signal to increase its intensity. The amplified electromagnetic wave signal is then modulated onto the local oscillator optical signal to produce a modulated signal.

[0063] The above-ground receiving module 401 receives the modulated signal from the underground receiving module 301 and then performs a de-skewing process on the modulated signal. The de-skewing process is to convert the position information of the detected cavity inner wall into a low-frequency intermediate frequency signal, reducing the subsequent data processing volume and achieving detection without close-range blind spots. Filtering is then performed to remove unnecessary frequency components and retain the useful signal part. Finally, signal processing is performed to obtain the target signal.

[0064] In summary, the ultra-high-precision underground cavity structure detection system proposed in the embodiments of this application reduces the amount of data processing by processing electromagnetic wave signals using a de-skewing reception technique. The delay of the adjustable optical delay line 4011 also solves the problem of radar blind spots at close range. This application effectively combines the advantages of microwave photonic technology for broadband signal generation, the flexible extension of optical fiber transmission signals, and microwave photonic de-skewing reception technology.

[0065] In some examples, the ground transmitting module 101 includes: a single-frequency laser 1011, a reference source 1012, a first electro-optical modulator 1013, an optical combining filter 1014, and an optical coupler 1015;

[0066] The single-frequency laser 1011 is used to generate an optical carrier;

[0067] The reference source 1012 is used to generate a linear frequency modulation signal;

[0068] The first electro-optical modulator 1013 is used to modulate the linear frequency modulation signal onto the optical carrier, adjust the bias voltage to a carrier suppression state, and adjust the amplitude of the linear frequency modulation signal to obtain an initial optical signal;

[0069] The optical combination filter 1014 is used to filter the initial optical signal to obtain an optical sideband signal;

[0070] The optical coupler 1015 is configured to split the optical sideband signal into a transmission optical signal and a local oscillator optical signal through a branching operation.

[0071] For example, the single-frequency laser 1011 generates an optical carrier with a frequency of f1. The reference source 1012 generates a linear frequency modulation signal with a center frequency of f0 and a bandwidth of B0. The first electro-optical modulator 1013 modulates the linear frequency modulation signal generated by the reference source 1012 onto the optical carrier generated by the single-frequency laser 1011. Electro-optical modulation can change certain characteristics of the optical carrier (such as amplitude and phase) so that it carries the information of the linear frequency modulation signal. By adjusting the bias voltage to a carrier suppression state, the amplitude of the optical carrier is suppressed to a lower level, thereby highlighting the modulated signal. By adjusting the amplitude of the linear frequency modulation signal, that is, adjusting the amplitude of the signal generated by the reference source 1012, the first-order optical sideband output by the first electro-optical modulator 1013 is suppressed, thereby obtaining the initial optical signal.

[0072] The optical combination filter 1014 is composed of a two-stage optical filter cascaded with an optical amplifier. The optical combination filter 1014 filters the initial optical signal obtained by the first electro-optical modulator 1013 to obtain an optical sideband signal. Its purpose is to select specific frequency components from the initial optical signal, that is, to select the positive and negative third-order sidebands output by the first electro-optical modulator 1013 through the optical combination filter 1014 to obtain the optical sideband signal. The optical combination filter 1014 can select a specific wavelength range or frequency range as needed to remove unnecessary signal components. The optical coupler 1015 divides the optical sideband signal into a transmitted optical signal and a local oscillator optical signal through a branching operation. The transmitted optical signal will be sent out for target detection, and the local oscillator optical signal will be used in the subsequent reception and processing process.

[0073] In some examples, the underground transmitting module 201 includes: a first photodetector 2011 and a low noise amplifier 2012;

[0074] The first photodetector 2011 is used to perform beat frequency processing on the emitted light signal to obtain an electrical signal;

[0075] The low noise amplifier 2012 is used to amplify the electrical signal to obtain an amplified electrical signal.

[0076] Exemplarily, the function of the first photodetector 2011 is to perform beat frequency processing on the transmitted optical signal from the ground transmitting module 101 to obtain an electrical signal. Beat frequency processing is a method of converting an optical signal into an electrical signal, usually by using the photoelectric effect to form an electric current. The low-noise amplifier 2012 amplifies the electrical signal output by the first photodetector 2011. Since the electrical signal may be attenuated or interfered with during transmission, the low-noise amplifier 2012 can enhance the signal strength and improve the signal-to-noise ratio. The characteristic of the low-noise amplifier 2012 is that while amplifying the signal, it minimizes the noise introduced by itself to ensure the quality of the signal. After amplification by the low-noise amplifier 2012, an amplified electrical signal is obtained. The low-noise amplifier 2012 then inputs the amplified electrical signal into the transmitting antenna, and the transmitting antenna transmits the amplified electrical signal into free space.

[0077] In some examples, the underground receiving module 301 includes: an electrical amplifier group 3011 and a second electro-optical modulator 3012;

[0078] The electric amplifier group 3011 is used to amplify the electromagnetic wave signal to obtain an amplified electromagnetic wave signal;

[0079] The second electro-optical modulator 3012 is used to modulate the amplified electromagnetic wave signal into the local oscillation optical signal to obtain a modulated signal.

[0080] Exemplarily, the electrical amplifier group 3011 amplifies the acquired electromagnetic wave signal to obtain an amplified electromagnetic wave signal. The purpose of amplification is to enhance the signal strength for subsequent processing. The electrical amplifier group 3011 is composed of a low-noise amplifier cascaded with an adjustable gain amplifier to enhance signal reception capabilities. The second electro-optical modulator 3012 modulates the electromagnetic wave signal amplified by the electrical amplifier group 3011 onto a local oscillator optical signal. Electro-optical modulation is a technology that uses an electric field to modulate the properties of light. Here, by modulating the electromagnetic wave signal onto the local oscillator optical signal, the information of the electromagnetic wave signal can be loaded into the optical signal for optical processing and transmission. After modulation, a modulated signal is obtained.

[0081] In some examples, the ground receiving module 401 includes: an adjustable optical delay line 4011, a second photodetector 4012, an intermediate frequency filter 4013, and a digital signal processor 4014;

[0082] The adjustable optical delay line 4011 is used to perform a time delay operation on the local oscillator optical signal;

[0083] The second photodetector 4012 is used to perform de-skewing reception processing on the modulated signal to obtain an intermediate frequency electrical signal;

[0084] The intermediate frequency filter 4013 is used to filter the intermediate frequency electrical signal to obtain a filtered electrical signal;

[0085] The digital signal processor 4014 is used to perform signal processing on the filtered electrical signal to obtain a target signal.

[0086] For example, adjustable optical delay line 4011 is used to delay the local oscillator (LO) optical signal. This delay can adjust the relative temporal relationship between the LO signal and the modulated signal. This is crucial for subsequent beat frequency and de-skew reception processing. By precisely adjusting the delay, the two signals can interact effectively at the appropriate time.

[0087] The second photodetector 4012 performs beat frequency and de-skewing processing on the modulated signal. Beat frequency processing mixes the signals to produce an electrical signal containing the frequency difference between the two. De-skewing converts the detected position information of the cavity inner wall into a low-frequency intermediate frequency signal, reducing the subsequent data processing workload and achieving close-range blind spot detection. Through de-skewing, the second photodetector 4012 converts the modulated signal in the optical domain into an intermediate frequency signal in the electrical domain.

[0088] IF filter 4013 filters the IF electrical signal, removing unwanted frequency components and noise. Based on the frequency characteristics of the target signal, IF filter 4013 selects appropriate passband and stopband to improve signal quality and signal-to-noise ratio. After filtering, the resulting filtered electrical signal is purer and more closely resembles the true characteristics of the target signal.

[0089] The digital signal processor 4014 performs further digital signal processing on the filtered electrical signal, including but not limited to amplification, digitization, demodulation, error correction and other operations to obtain the target signal.

[0090] In some examples, the initial optical signal is represented by:

[0091]

[0092] Among them, E lis the amplitude of the light wave from the laser, ω l is the angular frequency of the light wave from the laser, ω0 is the center frequency of the IF signal from the DDS, K0 is the chirp rate of the IF signal from the DDS, T is the time period of the IF signal from the direct digital frequency synthesizer, J 2n-1 (β1) is the first type (2n-1) nd Bessel function, β1 is the modulation index of the first electro-optical modulator 1013, and t is time.

[0093] Exemplarily, on the ground transmitter module 101, the optical signal generated by the reference source 1012 is modulated by the first electro-optical modulator 1013 (MZM1). The first electro-optical modulator 1013 is biased to zero by a potentiometer to suppress the optical carrier. A linear frequency modulation (LFM) signal at the intermediate frequency (IF) generated by a direct digital synthesizer (DDS) is applied to the radio frequency (RF) port of the first electro-optical modulator 1013 to modulate the intensity of the optical wave. The output signal of the first electro-optical modulator 1013, that is, the initial optical signal, is shown in Equation (1).

[0094] Among them, E l and ω l are the amplitude and angular frequency of the light wave from the single-frequency laser 1011; ω0, K0, and T are the center frequency, chirp rate, and time period of the IF signal from the DDS; J 2n-1 (β1) is the first type (2n-1) nd Bessel function, β1 is the modulation index of the first electro-optic modulator 1013, can be expressed as V π1 is the half-wave voltage of the electro-optic modulator (MZM), V RF is the amplitude of the IF signal from the DDS. When setting V RF The value of β1 satisfies β1≈3.8314, because J1(β1)=0, which means that the first-order optical sideband is suppressed. In this case, only ±3rd-order and higher-order sidebands exist at the output of the first electro-optical modulator 1013. By using the optical combining filter 1014 to eliminate the ±5th-order and higher-order sidebands, an optical sideband signal is obtained. The spectrum will only contain ±3rd-order sidebands, that is, the optical sideband signal is expressed as:

[0095]

[0096] Then, the optical signal is divided into two parts: one part is sent to the underground receiving module 301 as the local oscillator signal, and the other part is sent to the first photodetector 2011 to generate the beat frequency to obtain the electrical signal, that is, the radar detection signal, which can be given by the following formula:

[0097]

[0098] In the underground receiving module 301, the local oscillator signal is modulated by the input echo reflected from the measurement target through the second electro-optical modulator 3012, also known as the quadrature-point biased electro-optical modulator (MZM2). The received electromagnetic wave signal, i.e., the echo, is collected by the receiving antenna and amplified by the electrical amplifier group 3011 before being input into the second electro-optical modulator 3012. To address the conflict between the detection range and bandwidth of the high-effective-bit-number analog-to-digital converter (ADC), an adjustable optical delay line 4011 (OTD) is used to delay the optical local oscillator signal. The delayed optical signal can be expressed as:

[0099]

[0100] Among them, E l' and τ are the electric field strength of the optical local oscillator signal and the time delay of OTD respectively. The echo received by the receiving antenna can be expressed as:

[0101]

[0102] Among them, t R is the time delay experienced by the input echo in free space, V evo is the amplitude of the input echo.

[0103] In some examples, the modulated signal is represented by:

[0104]

[0105] Where Δφ represents the phase difference between the two arms of the second electro-optic modulator 3012, V π2 is the half-wave voltage of the second electro-optic modulator 3012, V eco (t) represents the electromagnetic wave signal received by the receiving antenna, E l' (t) is the delayed optical signal.

[0106] Exemplarily, after being modulated by the input echo, the optical signal at the output of the second electro-optical modulator 3012 (MZM2) is as shown in equation (6), where Δφ represents the phase difference between the two arms of the second electro-optical modulator 3012. When When , the second electro-optic modulator 3012 is in quadrature point bias. t1=t-τ, t2=tt R , assuming that the input echo is a small signal, the above equation can be expanded according to the first-kind Bessel function:

[0107]

[0108] The optical sideband represented by the first term is close to the optical sideband represented by the fifth term in the frequency domain, and the optical sideband represented by the third term is close to the optical sideband represented by the fourth term in the frequency domain. Therefore, after being beat by the second electro-optical modulator 3012, the beat frequencies of the two sets of optical sidebands are low, while the beat frequencies of the other optical sidebands are high. After filtering by the intermediate frequency filter 4013, the electrical signal can be expressed as:

[0109]

[0110] It can be seen that the frequency of the final electrical signal is f0=6K0(τ-t R ) is proportional to the difference between the delay generated by the echo signal and the delay generated by the target. Due to the limited bandwidth of the low-pass filter (LPF), the target delay t R , through OTD conversion, to ensure that the final signal frequency f0 is within the bandwidth of LPF.

[0111] The above theory was experimentally verified. The instruments used in the designed experiment include: CoBriteDX1 semiconductor laser, PSS5R8B frequency source, electro-optic modulator (AX-0MSS-20-PFA-PFA-LV, EOSPACE), Waveshaper16000A programmable optical filter, optical amplifier, low-noise amplifier, adjustable gain amplifier, Teraxion bandpass filter, photodetector (Finisar, XPDV2120RA), adjustable optical delay, AQ6370D optical spectrum analyzer, and spectrum analyzer (Keysight, N9030A).

[0112] Set the tunable laser center wavelength to 1550nm and the frequency to 193.4144THz; set the PSS5R8B reference source signal duration to 150μs, the emission bandwidth to 1GHz, and the center frequency to 5.83333GHz; adjust the potentiometer to make the electro-optical modulator work at the minimum bias point; set the optical band-stop filter parameters to have a center wavelength of 1550.028nm and a stopband width of 0.163nm; set the tunable optical bandpass filter frequency to 193.4109THz and a bandwidth of 10GHz. The spectrum output after the filter is as follows: Figure 2 As shown, this is a spectrum diagram output after passing through an optical combination filter in an ultra-high precision underground cavity structure detection system provided by this application; the optical amplifier amplification factor is set to 18.4dB; and instructions are sent through a computer to specify the delay of the tunable delay device to be 1.5km.

[0113] A 50:50 optical coupler 1015 is used to split the optical sideband into two parts: one part is used as the local oscillator signal to enter the receiving part, and the other part is used in the transmitting part to generate the LFM signal through the high-frequency PD beat frequency. The amplifier increases the power of the LFM signal to 47dBm for long-range target detection. Figure 3 As shown in the figure, it is a spectrum diagram of the LFM signal generated in the ultra-high precision underground cavity structure detection system provided by the present application. The spectrum of the final LFM signal measured by the spectrum analyzer (Keysight, N9030A) is shown. The center frequency of the broadband signal is 5.83333 GHz and the bandwidth is 1.6667 GHz. After frequency multiplication, the theoretical value of the center frequency is 34.99998 GHz and the bandwidth is 10 GHz; the actual value is a center frequency of 35 GHz and a bandwidth of 10 GHz, which is consistent with the theory. The time-width-bandwidth product (TBWP) of the generated radar waveform is 1,503,000.

[0114] The transmission and reception of RF signals are accomplished by two conical horn antennas. The amplifier group in the receiver consists of a low-noise amplifier and an adjustable-gain amplifier, both with a maximum gain of 40dB. The bandwidth of the MZM2 is 65GHz, and its operation is controlled by a bias controller (YYLabs, mini-MBC3). In order to ensure that the received signal still has a small frequency after the de-skewed photon signal is received, a section of low-loss optical fiber of known length can be added before the electro-optical modulator in the radar receiver. The time delay introduced by the optical fiber can be used to compensate for the time delay of the radar signal propagating in the environment, thereby reducing the de-skew frequency. The principle of de-skewed reception is as follows: Figure 4 The figure shows the principle diagram of the microwave photon de-skewing receiving technology used in the ultra-high-precision underground cavity structure detection system provided by this application. The signal is then modulated onto an optical carrier and de-skewing is performed at the beat frequency of the echo signal at PD2. The signal is then filtered by an intermediate frequency bandpass filter (2MHz-200MHz, BJQX, PSIPA1733001), and the filtered signal is processed by a 500MSa / s 12-bit ADC.

[0115] The performance of the ultra-high precision underground cavity structure detection radar based on microwave photon technology was then tested. The radar's distance resolution was tested using two metal reflectors at a distance of 2 cm between them. Figure 5 Figure 2 shows the resolution test results obtained by de-skewing single-cycle echo signals from two adjacent targets in an ultra-high-precision underground cavity structure detection system provided by this application. The figure shows the resolution test results obtained after de-skewing single-cycle echo signals from the reflector. The calculated distance between the two highest peaks is 1.8 cm, which is close to the actual value and theoretical resolution (1.5 cm) of the demonstrator.

[0116] In the process of scanning and detecting the cavity layer by layer, the echo signal of each scan is first processed to obtain the surrounding structure of the cavity layer at this height, and then a three-dimensional model of this height layer is constructed. Then, the three-dimensional models of each scan are accumulated. After scanning the last height layer, the three-dimensional structure of the entire cavity can be obtained, the volume of the cavity can be calculated, and other required geometric parameters can be obtained.

[0117] like Figure 6 FIG. 1 is a flow chart of an ultra-high-precision underground cavity structure detection method proposed in this application, and the method includes:

[0118] S110, obtaining an optical sideband signal;

[0119] S120, dividing the optical sideband signal into a transmission optical signal and a local oscillator optical signal through a branching operation;

[0120] S130, converting the transmitted optical signal into an electrical signal by beat frequency, and amplifying the electrical signal to obtain an amplified electrical signal;

[0121] S140, transmitting the amplified electrical signal through an antenna, detecting the signal using a layer-by-layer scanning method, and receiving the transmitted electromagnetic wave signal using a receiving antenna;

[0122] S150, amplifying the electromagnetic wave signal and modulating it into the local oscillation light signal to obtain a modulated signal;

[0123] S160: Perform de-skewing, filtering, and signal processing on the modulated signal to obtain a target signal.

[0124] The effects of the above method when applying the above system can be found in the description of the above system embodiment, which will not be repeated here.

[0125] like Figure 7 As shown, an embodiment of the present application also provides an electronic device 300, including a memory 310, a processor 320, and a computer program 311 stored in the memory 310 and executable on the processor. When the processor 320 executes the computer program 311, the steps of any of the above-mentioned methods for ultra-high precision underground cavity structure detection are implemented.

[0126] Since the electronic device introduced in this embodiment is a device used to implement an ultra-high precision underground cavity structure detection device in the embodiment of this application, based on the method introduced in the embodiment of this application, technical personnel in this field can understand the specific implementation of the electronic device of this embodiment and its various variations. Therefore, how the electronic device implements the method in the embodiment of this application will not be introduced in detail here. As long as the equipment used by technical personnel in this field to implement the method in the embodiment of this application falls within the scope of protection of this application.

[0127] In the specific implementation process, the computer program 311 can be implemented when executed by the processor Figure 1 Any implementation manner in the corresponding embodiments.

[0128] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0129] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-readable program code.

[0130] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0131] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0132] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0133] An embodiment of the present application further provides a computer program product, which includes computer software instructions. When the computer software instructions are executed on a processing device, the processing device executes the process of the LDPC decoding method of the solid-state drive controller.

[0134] A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function according to the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that a computer can store or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid state drive (SSD)).

[0135] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0136] In the several embodiments provided in this application, it should be understood that the disclosed devices, apparatuses and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0137] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0138] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0139] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the various embodiments of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0140] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

[0141] Although the preferred embodiments of this specification have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of this specification.

[0142] Obviously, those skilled in the art may make various changes and modifications to this specification without departing from the spirit and scope of this specification. Thus, if such changes and modifications fall within the scope of the claims of this specification and their equivalents, this specification is intended to include such changes and modifications.

Claims

1. An ultra-high precision underground cavity structure detection system, characterized in that: The system comprises: A ground transmitting module, the ground transmitting module is used to generate an optical sideband signal and split the optical sideband signal into a transmitting optical signal and a local oscillator optical signal through a branching operation; An underground transmitting module, configured to convert the transmitted optical signal into an electrical signal by beat frequency conversion, amplify the electrical signal to obtain an amplified electrical signal, and transmit the amplified electrical signal through an antenna; an underground receiving module, the underground receiving module being used to acquire an electromagnetic wave signal, amplify the electromagnetic wave signal, and modulate the electromagnetic wave signal onto the local oscillation optical signal to obtain a modulated signal, the electromagnetic wave signal being obtained by reflecting the amplified electrical signal from a target; The ground receiving module is used to perform de-skewing receiving processing, filtering processing and signal processing on the modulated signal to obtain a target signal.

2. The ultra-high precision underground cavity structure detection system according to claim 1, characterized in that: The ground transmission module includes: a single-frequency laser, a reference source, a first electro-optical modulator, an optical combination filter and an optical coupler; The single-frequency laser is used to generate an optical carrier; The reference source is used to generate a linear frequency modulation signal; The first electro-optical modulator is used to modulate the linear frequency modulation signal onto the optical carrier, adjust the bias voltage to a carrier suppression state, and adjust the amplitude of the linear frequency modulation signal to obtain an initial optical signal; The optical combination filter is used to filter the initial optical signal to obtain an optical sideband signal; The optical coupler is used to divide the optical sideband signal into a transmission optical signal and a local oscillator optical signal through a branching operation.

3. The ultra-high precision underground cavity structure detection system according to claim 1, characterized in that: The underground transmission module includes: a first photodetector and a low noise amplifier; The first photodetector is used to perform beat frequency processing on the emitted light signal to obtain an electrical signal; The low noise amplifier is used to amplify the electrical signal to obtain an amplified electrical signal.

4. The ultra-high precision underground cavity structure detection system according to claim 1, characterized in that: The underground receiving module includes: an electrical amplifier group and a second electro-optical modulator; The electric amplifier group is used to amplify the electromagnetic wave signal to obtain an amplified electromagnetic wave signal; The second electro-optical modulator is used to modulate the amplified electromagnetic wave signal into the local oscillation optical signal to obtain a modulated signal.

5. The ultra-high precision underground cavity structure detection system according to claim 1, characterized in that: The ground receiving module includes: an adjustable optical delay line, a second photodetector, an intermediate frequency filter and a digital signal processor; The adjustable optical delay line is used to perform a time delay operation on the local oscillator optical signal; The second photodetector is used to perform de-skewing reception processing on the modulated signal to obtain an intermediate frequency electrical signal; The intermediate frequency filter is used to filter the intermediate frequency electrical signal to obtain a filtered electrical signal; The digital signal processor is used to perform signal processing on the filtered electrical signal to obtain a target signal.

6. The ultra-high precision underground cavity structure detection system according to claim 2, characterized in that: The initial optical signal is expressed as: Among them, E l is the amplitude of the light wave from the laser, ω l is the angular frequency of the light wave from the laser, ω0 is the center frequency of the IF signal from the DDS, K0 is the chirp rate of the IF signal from the DDS, T is the time period of the IF signal from the direct digital frequency synthesizer, J 2n-1 (β1) is the first type (2n-1) nd Bessel function, β1 is the modulation index of the first electro-optic modulator, and t is time.

7. The ultra-high precision underground cavity structure detection system according to claim 3, characterized in that: The modulated signal is expressed as: where ΔΦ represents the phase difference between the two arms of the second electro-optic modulator, V π2 is the half-wave voltage of the second EO modulator, V eco (t) represents the electromagnetic wave signal received by the receiving antenna, E l , (t) is the delayed optical signal.

8. An ultra-high precision underground cavity structure detection method, characterized in that: The method comprises: Acquire optical sideband signal; Splitting the optical sideband signal into a transmitted optical signal and a local oscillator optical signal through a branching operation; Converting the emitted light signal into an electrical signal by beat frequency, and amplifying the electrical signal to obtain an amplified electrical signal; The amplified electrical signal is transmitted through an antenna, and a layer-by-layer scanning method is used for detection, and the transmitted electromagnetic wave signal is received by a receiving antenna; amplifying the electromagnetic wave signal and modulating it into the local oscillator light signal to obtain a modulated signal; The modulated signal is subjected to de-skewing receiving processing, filtering processing and signal processing to obtain a target signal.

9. An electronic device comprising: A memory and a processor, characterized in that the processor is used to implement the steps of an ultra-high precision underground cavity structure detection method as described in claim 8 when executing the computer program stored in the memory.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the ultra-high precision underground cavity structure detection method as described in claim 8 are implemented.

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