A portable plate microwave imaging device and method

Abstract

This invention provides a portable plate-type microwave imaging device and method, comprising a controller, an RF switch, and a detector; the controller is connected to the detector via the RF switch. The controller includes a display unit, an MCU module, a signal generator, and a mixer unit; the detector has a support and a microwave antenna; the RF switch has a switch switching module for sequentially or out-of-order switching of the microwave antenna connections; the controller also integrates an analog-to-digital converter (ADC), which is connected to the receiver of the RF switch. This invention features a simple structure, low cost, good portability, and ease of movement; combined with multi-stage mixed signal processing, it can achieve high-resolution imaging, relying on backscattering for imaging, and uses low-energy microwaves that do not produce thermal effects.

Description

Technical Field

[0001] This invention relates to the field of general image data processing or generation technology, and specifically to a portable plate-type microwave imaging device and method. Background Technology

[0002] Existing computed tomography (CT) and fMRI are generally large-scale devices, housed in specific institutions. These devices are complex to use, involve lengthy examination processes, and have poor portability. Specifically:

[0003] (1) Long detection time. The time spent includes the time from the discovery of the problem to the solution of the problem. For example, CT and fMRI are large and inconvenient to move, and the detection needs to be carried out in a specific location, resulting in long detection time. The time spent also refers to the long detection process itself. For example, the electrodes need to be moistened and placed, which leads to long detection time.

[0004] (2) The detection range is not wide. For example, volume impedance phase-shift spectroscopy has limited application scenarios.

[0005] Therefore, existing research focuses on microwave detection and imaging technology. Microwaves, due to their high frequency, short wavelength, and good directionality, can be used to create images by measuring the dielectric constant distribution of different objects they pass through. However, microwave detection and imaging carries the risk of secondary damage. Therefore, to avoid the problem of the target moving repeatedly during detection, existing microwave detection methods use a ring structure. However, this structure is complex and makes device movement inconvenient; even during full-angle detection, the target still needs to move to complete the detection.

[0006] In summary, there is still a need to design a microwave detection and imaging device that is portable and has advantages such as accurate scanning, wide applicability, ability to distinguish multiple types, and low cost. Summary of the Invention

[0007] This invention addresses the problems existing in the prior art by providing a device with a simple structure and low cost that can perform microwave detection and imaging of targets, and achieves accurate imaging by combining specific methods.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] On one hand, the present invention provides a portable plate-type microwave imaging device, which mainly includes a controller, a radio frequency switch and a detector; the controller is connected to the detector through the radio frequency switch;

[0010] The controller is configured with a display unit, an MCU module, a signal generator, and a mixer unit; the MCU module is used to generate, receive, calculate, and store signals; the display unit is connected to the MCU module and is equipped with a display screen and a human-machine interface; the signal generator is connected to both the MCU module and the mixer unit.

[0011] The detector is equipped with a bracket and a microwave antenna; the bracket has a U-shaped clamp structure, and multiple microwave antennas are evenly distributed on both sides of the clamp.

[0012] The radio frequency switch is equipped with a switch switching module, which is used to switch the connection relationship of the microwave antenna sequentially or out of order; the connection relationship includes a first connection relationship and a second connection relationship.

[0013] In the first connection relationship, at least one microwave antenna is connected to the transmitting end of the radio frequency switch, and the number of connected antennas is less than the number of microwave antennas on a single side plate.

[0014] In the second connection relationship, the microwave antenna is connected to the receiving end of the radio frequency switch;

[0015] The controller also integrates an analog-to-digital converter, which is connected to the receiver of the radio frequency switch.

[0016] Optionally, the main control chip of the MCU module is an embedded microcontroller chip;

[0017] The signal generator is equipped with an radio frequency chip;

[0018] The mixing unit is equipped with a mixer chip;

[0019] The mixing unit is connected to the MCU module and the signal generator respectively.

[0020] Optionally, the microwave antenna array is distributed on the two side plates of the bracket;

[0021] The number of microwave antennas on both sides of the bracket is the same and they are symmetrically distributed.

[0022] Optionally, the microwave antenna on one side of the bracket is an n×n planar array antenna, where n is a natural number and .

[0023] Optionally, at least m antenna mounting positions are left empty in the middle of the planar array antenna on one side of the bracket, where m is a natural number. .

[0024] Optionally, the RF switch may also include a power amplifier and a reflective bridge;

[0025] The power amplifier is connected to the mixer unit and the reflection bridge, respectively.

[0026] The reflective bridge is also connected to the controller and the switch switching module respectively;

[0027] An amplitude and phase detection chip is also connected in series between the analog-to-digital converter and the receiving end of the radio frequency switch.

[0028] The two input terminals of the amplitude and phase detection chip are respectively connected to the output terminal of the reflective bridge and the receiving terminal of the radio frequency switch; the output terminal of the amplitude and phase detection chip is connected to the analog-to-digital converter.

[0029] On the other hand, the present invention also provides a portable plate-type microwave imaging method for imaging with the aforementioned portable plate-type microwave imaging device, which mainly includes the following steps:

[0030] Adjust the above device so that the target to be inspected is located in the detection area;

[0031] The controller generates a transmission signal that is a mixture of high-frequency and low-frequency signals.

[0032] The transmitted signal is sent sequentially or out of order to at least one microwave antenna through a switching module in the radio frequency switch; the microwave antenna in the non-transmitting state receives the feedback signal and transmits the feedback signal to the radio frequency switch;

[0033] The feedback signal is mixed through multiple stages to obtain a mixed signal, and the mixed signal is converted into a mixed digital signal by an analog-to-digital converter.

[0034] The MCU module processes the hybrid digital signal based on a delay-multiplication-superposition summation algorithm and obtains the processed signal;

[0035] A heat map is drawn based on the processed signal, and the heat map is used as a target microwave imaging map.

[0036] Optionally, the MCU module in the controller generates a low-frequency signal with a frequency range of less than 30MHz;

[0037] The controller contains a signal generator that produces high-frequency signals, with a frequency range of 30MHz-6GHz.

[0038] The low-frequency signal and the high-frequency signal are mixed by a mixing unit to obtain the transmitted signal, and the signal frequency range is 10MHz-6GHz.

[0039] Optionally, the feedback signal is mixed through multiple stages of frequency mixing to obtain a mixed signal, including the following steps:

[0040] The reference clock signal outputs the first local oscillator signal through a phase-locked loop; the reference clock signal outputs the second local oscillator signal through a clock generator.

[0041] The transmitted signal is mixed with the first local oscillator signal to obtain a reference first mixed signal and a reflected first mixed signal, respectively. The reference first mixed signal is then mixed with the second local oscillator signal to obtain a reference second mixed signal.

[0042] The feedback signal is mixed with the first local oscillator signal to obtain a received first mixed signal; the reflected first mixed signal and the received first mixed signal are filtered, and the filtering result is mixed with the second local oscillator signal to obtain a received second mixed signal;

[0043] The feedback signal is compared with the transmitted signal in amplitude and phase to obtain amplitude-phase difference data;

[0044] The mixed signal includes the reference second mixing signal, the received second mixing signal, and the amplitude-phase difference data;

[0045] The hybrid digital signal processing based on the delayed multiplication and superposition algorithm includes the following steps:

[0046] The amplitude of the hybrid digital signal is adjusted to obtain an equivalent signal;

[0047] The equivalent signal is processed based on the autocorrelation function, and then the beamforming signal is obtained through beamforming operation.

[0048] The processed signal is obtained by performing logarithmic and gamma transformations on the beamforming signal.

[0049] Optionally, the feedback signals are received in pairs, and the equivalent signal formula of the mixed digital signal is:

[0050] ;

[0051] In the formula, For each pair of received signals and The equivalent microwave signal.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] This invention features a simple structure and low cost. The device employs a plate-type antenna design, reducing its size and making it portable. It can be quickly moved according to imaging needs; scanning and imaging can be performed simply by clamping the transceiver antenna plates to both sides of the target, eliminating the risk of secondary damage. High-resolution images can be achieved through microwave antenna transmission and reception on the clamp plate, combined with multi-stage hybrid signal processing. This is because the total distance from the antenna to the detection points in the front and rear loops differs significantly, allowing for accurate feature differentiation using microwave technology. Furthermore, microwave energy does not directly generate current but forms a composite electromagnetic field path. This device relies on backscattering for imaging, utilizing low-intensity microwave energy to avoid thermal effects. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the device in a specific embodiment of the present invention;

[0056] Figure 2 This is a schematic diagram of the signal flow in a specific embodiment of the present invention;

[0057] Figure 3 This is a circuit diagram in a specific embodiment of the present invention;

[0058] Figure 4 This is a simulation result diagram of the model at 5cm in a specific embodiment of the present invention;

[0059] Figure 5 This is a simulation result diagram of the 3cm model in a specific embodiment of the present invention.

[0060] In the diagram: 1. Microwave antenna #1, 2. Microwave antenna #2, 3. Microwave antenna #3, 4. Microwave antenna #4, 5. Microwave antenna #5, 6. Microwave antenna #6, 7. Microwave antenna #7, 8. Microwave antenna #8, 9. Microwave antenna #9, 10. Microwave antenna #10, 11. Microwave antenna #11, 12. Microwave antenna #12, 13. Microwave antenna #13, 14. Microwave antenna #14, 15. Microwave antenna #15, 16. Microwave antenna #16, 17. MCU module, 18. RF switch. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0063] In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0064] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0065] It is worth noting that, unless otherwise specified, the methods used in this invention are all conventional methods; and the raw materials and equipment used are all conventional commercially available products, and their sources are not specifically limited.

[0066] On the one hand, such as Figure 1 As shown, this embodiment provides a portable plate-type microwave imaging device, which mainly includes a controller, an RF switch, and a detector. The controller 17 is connected to the RF switch 18 via a coaxial cable, and the RF switch 18 is also connected to the detector via a coaxial cable.

[0067] The controller 17 is equipped with a display unit, an MCU module, a signal generator, and a mixer unit. Optionally, the MCU module is used to generate, receive, calculate, and store signals. Therefore, this embodiment selects a microcontroller as the MCU module, whose base is a multi-interface electronic circuit board, configured with typical circuitry of an STM32 minimum system board, and includes various functional components such as a processor, memory, and timers. In this embodiment, the main control chip (processor) of the MCU module is an embedded microcontroller chip, optionally an STM32 chip. The display unit is connected to the MCU module and is a color touch screen used to display target microwave imaging and provide a human-machine interface for convenient operation.

[0068] The signal generator is connected to both the MCU module and the mixer unit; optionally, the signal generator is equipped with an RF chip, preferably the MAX2871 chip.

[0069] The mixing unit is equipped with a mixer chip; preferably an LTC5510 chip, and the mixing unit is connected to both the MCU module and the signal generator.

[0070] The detector is equipped with a support and a microwave antenna. For example... Figure 1 As shown, the bracket has an inverted U-shaped clamp structure, with multiple microwave antennas evenly distributed on both sides of the clamp. The two clamps are symmetrically arranged, and the three-dimensional cubic space enclosed between the two clamps serves as the detection area. For portability considerations, in this embodiment, the length of the upper connecting horizontal plate of the U-shaped clamp is designed to range from 25cm to 50cm (matching common target sizes). A step-by-step strategy can be adopted, with pre-producing horizontal plates of multiple specifications (25cm, 30cm, 35cm, 40cm, 45cm, 50cm, and 55cm) for selection. The two side clamps are connected to the upper connecting horizontal plate via a detachable connection structure, with the width of the matching sheet material ranging from 15cm to 25cm. The overall thickness of the U-shaped clamp ranges from 3cm to 6cm. Optionally, the microwave antenna array is distributed on both sides of the bracket, with the same number of microwave antennas on each side, symmetrically distributed along the center line of the U-shaped clamp, meaning that each microwave antenna has one antenna on its opposite side laterally.

[0071] Furthermore, based on the above settings, the microwave antenna on one side of the bracket is an n×n planar array antenna, where n is a natural number and Specifically, for ease of understanding, this embodiment is as follows: Figure 1 As shown, n is selected as 3, thus 3×3 (a total of 9) mounting positions are evenly distributed on the inner surface of each side plate. Furthermore, unlike the conventional full-coverage design, this embodiment further optimizes and improves the antenna arrangement based on the following factors: a blank space is left in the middle area, without installing a microwave antenna. The main factors are:

[0072] Near-field effect: When multiple antennas are closely arranged, the near-field effect can change the antenna's radiation characteristics and impedance, thus affecting its performance and signal transmission. Leaving gaps in between can reduce the impact of the near-field effect, allowing the antennas to maintain stable performance within their respective operating frequency bands, reducing interference to other antennas, and improving the stability and reliability of the entire antenna system.

[0073] Adapting to subsequent algorithms: The layout with gaps in the middle is more conducive to the processing and analysis of microwave signals by subsequent algorithms. Furthermore, the gaps allow the microwave signal to cover the detection area more evenly during propagation, avoiding excessive concentration or cancellation of signals in certain areas due to overly dense antennas. This allows for better utilization of the microwave signal, improving imaging quality and detection effectiveness.

[0074] Reduce the number of antennas: While ensuring effective detection coverage, reducing the number of antennas can lower costs.

[0075] Closer to the head area: The human head is approximately spherical, and an antenna array with a gap in the middle can avoid the problem of excessive microwave intensity in the central area. This allows the spacing between the U-shaped plates to be designed to be smaller, which in turn brings the outer microwave antenna closer to the surface of the head. This reduces signal attenuation and reflection differences caused by inconsistent distances, thereby improving signal transmission efficiency and detection accuracy.

[0076] Therefore, in this embodiment, at least m antenna mounting positions are left empty in the middle of the planar array antenna on one side of the bracket, where m is a natural number. To ensure the detection area is covered by the microwave antenna, a regular (square) area, such as 1, can be reserved in the center. , ... Multiple empty spaces are left in the center. In this embodiment, n is 3, so m is 1; therefore, the microwave antenna distribution rule is a U-shaped distribution with one empty space in the middle, as shown below. Figure 1 As shown, eight microwave antennas are sequentially distributed on the left side of the clamp: microwave antenna 1#1, microwave antenna 2#2, microwave antenna 3#3, microwave antenna 4#4, microwave antenna 5#5, microwave antenna 6#6, microwave antenna 7#7, and microwave antenna 8#8 (microwave antenna z#z represents the z-th microwave antenna, and is labeled z in the attached diagram). Similarly, eight microwave antennas are also sequentially distributed on the right side of the clamp: microwave antenna 9#9, microwave antenna 10#10, microwave antenna 11#11, microwave antenna 12#12, microwave antenna 13#13, microwave antenna 14#14, microwave antenna 15#15, and microwave antenna 16#16.

[0077] A total of 16 microwave antennas are connected to RF switch 18 via coaxial cables. RF switch 18 is equipped with a switch switching module, which is a switch switching circuit used to switch the connection relationship of the microwave antennas sequentially or out of order; the connection relationship includes a first connection relationship and a second connection relationship.

[0078] In the first connection relationship, this embodiment connects a microwave antenna to the transmitting end of the RF switch in a preset order; in the second connection relationship, other non-transmitting microwave antennas are connected to the receiving end of the RF switch.

[0079] Optional, combined Figure 2 and Figure 3As shown, the RF switch 18 also includes a power amplifier (PA block) and a reflector bridge. The power amplifier is connected to both the mixer unit and the reflector bridge, and an adjustable attenuator RFSA3714 is connected in series before the power amplifier device PA to adjust the signal power. The reflector bridge is also connected to the controller and the switch switching module (switch transmitter). The controller 17 in this embodiment integrates a reference clock with a clock frequency of 27MHz, and provides clock signals (PLL references) to multiple phase-locked loops (PLLs) to generate various required reference signals, i.e., local oscillator signals. The PLLs include PLL1 (a clock generator with integrated circuit model SI5351), PLL PLLA (an integrated circuit model MAX2871), and PLL PLLB (an integrated circuit model MAX2871). Phase-locked loops (PLL1) and PLLA provide low-frequency reference signals (<30MHz) and high-frequency reference signals (30MHz-6GHz), respectively. These signals are filtered by a 2-to-1 selection circuit (an analog switch constructed from CMOS devices in this embodiment). The filtered signals are then provided to an adjustable attenuator for preprocessing the mixed signal. A 1-to-2 power divider is connected in series after the power amplifier to distribute the signal. The two distributed paths are then connected to a reflector bridge and a mixer (X) connected to one output of the PLL1.

[0080] The controller 17 also integrates an analog-to-digital converter (ADC) for power detection and ADC acquisition. The ADC is connected to the receiver of the RF switch, and an amplitude-phase detection chip (model AD8302) is connected in series between the ADC and the receiver of the RF switch. The two inputs of the amplitude-phase detection chip are connected to the output of the reflector bridge and the receiver of the RF switch, respectively. In this embodiment, the reflector bridge has two outputs: one output is split into two paths by a 1-to-2 power divider, connected to the transmitter (port 1, P1: transmit, reflect) and the amplitude-phase difference reference of the amplitude-phase detection chip, respectively; the other output is connected to a mixer (X) connected to one output of the phase-locked loop (PLLB). The output of the amplitude-phase detection chip is connected to the ADC.

[0081] The analog-to-digital converter (ADC) is also connected to a reflector bridge to acquire the transmitted signal as one of the reference signals. The connection structure is as follows: the receiver end of the RF switch, i.e., port 2 (P2: receive), is connected to a two-stage 2-to-1 multiplexer consisting of a direct-connect channel and a low-noise amplifier (LNA), and then connected to a mixer (X) connected to one output of the phase-locked loop (PLL1). This mixer, along with the reflector bridge and the PLL1, is then output to the receiver channel via a 2-to-1 multiplexer. The receiver channel and the output of the PLL1 are connected to a programmable gate amplifier (PGA) via mixer (X), and then to the ADC. Additionally, the PLL1 has another output line connected to mixer (X) that connects to the PLL1 and the reflector bridge. This mixer (X) is then connected to the ADC via another mixer (X) and serves as a drive reference signal for the ADC's ADC.

[0082] In this embodiment, a portable plate-type microwave imaging method is also provided based on the aforementioned device, which mainly includes the following steps:

[0083] First, invert and adjust the aforementioned device so that the target is located within the detection area. It is understood that once the target to be detected is in a suitable position and orientation, it does not need to be moved; only the device position needs adjustment. The device can be placed flat or suspended by a multi-axis hanger.

[0084] The MCU module in controller 17 generates a low-frequency signal with a range of less than 30MHz; the MCU module also controls the signal generator to generate a high-frequency signal with a range of 30MHz-6GHz; the two signals are mixed by a subsequently connected mixing unit to obtain a transmission signal with a frequency range of 10MHz-6GHz.

[0085] The transmitted signal enters the RF switch, passes through the power amplifier and the reflector bridge, and then enters the transmitting end. The switching module sequentially connects each microwave antenna, meaning that microwave antennas 1# through 16# are connected at fixed time intervals. During this period, when each microwave antenna is not transmitting, it is connected to the receiving end by the switching module and acts as a microwave receiver. However, in this embodiment, to simplify the switching module, the design only connects all microwave antennas on the opposite side to the receiving end during the switching process. For example, when microwave antenna 1# is transmitting, microwave antennas 9# through 16# are connected to the receiving end, while microwave antennas 2# through 8# are not involved in operation.

[0086] The feedback signal received by the receiver from the microwave is mixed through multiple stages of frequency mixing to obtain a mixed signal, which is then converted into a mixed digital signal by an analog-to-digital converter. The process of obtaining the mixed signal from the feedback signal through multiple stages of frequency mixing includes the following steps:

[0087] refer to Figure 3As shown, the transmit signal after the power divider 1 is split into 2 is used as a reference and mixed with the first local oscillator signal of the phase-locked loop PLLB to obtain the reference first mixer signal; the signal of the reflection bridge is mixed with the first local oscillator signal of the phase-locked loop PLLB to obtain the reflection first mixer signal; the reference first mixer signal is mixed with the second local oscillator signal of the phase-locked loop PLL1 to obtain the reference second mixer signal;

[0088] The feedback signal is repeatedly selected from two by an LNA low-noise amplifier, and then split into two paths. One path is mixed with the first local oscillator signal to obtain the received first mixed signal. The reflected first mixed signal and the received first mixed signal are then filtered. When the reflected first mixed signal is selected, one type of coefficient of microwave propagation coefficient is obtained, and when the received first mixed signal is selected, another type of coefficient is obtained. Then, the above filtering result is mixed with the second local oscillator signal to obtain the received second mixed signal. The other path is compared with the transmitted signal in amplitude and phase to obtain amplitude and phase difference data.

[0089] Therefore, the mixed signal includes a reference second mixing signal, a received second mixing signal, and amplitude-phase difference data.

[0090] The MCU module processes the mixed digital signal based on a delay-multiplication-superposition algorithm to obtain the processed signal; the processing of the mixed digital signal based on the delay-multiplication-superposition algorithm includes the following steps:

[0091] In this embodiment, the reference second mixer is the transmitted signal x, and the received second mixer is the received signal s. The amplitude of the mixed digital signal is adjusted to obtain an equivalent signal. Specifically, in this embodiment, due to the control of the device's switching module, only eight antennas receive the same transmitted signal. That is, the transmitted microwave signal. That is, experience The received signal after a delay. Therefore, the amplitude adjustment is: calculate the received signal for each pair. The square root of the absolute value yields the equivalent microwave signal with the same dimension after scaling. The formula is:

[0092] ;

[0093] The equivalent signal is processed based on the autocorrelation function, and then the beamforming signal is obtained through beamforming operations. Specifically, the beamforming signal is obtained through the autocorrelation function. The formula is:

[0094] ;

[0095] Finally, envelope detection can be performed on the beamforming signal. Envelope information can be extracted using the `envelope` function in MATLAB. The processed signal is obtained by performing logarithmic and gamma transformations on the beamforming signal. Logarithmic transformation involves applying a log operation to the original signal, while gamma transformation involves applying an exponential operation. Envelope detection is used to plot the amplitude changes of the transmitted and received signals over time. By comparing the differences in their envelopes, the amplitude and phase differences between the transmitted and received signals can be calculated and used to compare or correct the aforementioned amplitude and phase difference data.

[0096] A heatmap is generated based on the processed signal. The space between the antennas is divided into 1mm×1mm×1mm finite elements. The signal strength at each finite element is calculated based on the processed signal and its delay. Different intensities are mapped to color values ​​in the heatmap, and the heatmap serves as the target microwave imaging map. Specifically, the signal delay can be obtained by calculating the phase difference using the aforementioned amplitude and phase difference data; the signal attenuation can be obtained by calculating the amplitude difference; and the intensity of the superimposed signals with different attenuations can be obtained by aligning and canceling the delay. This intensity is then mapped to the color values ​​in the heatmap.

[0097] Based on the above method, simulations were performed using FEKO three-dimensional full-wave electromagnetic simulation software, and the results are as follows. Figure 4 , 5 As shown in the figure, a simulation test was conducted using a 1.8 GHz FMCW wave. The size of the target was adjusted in the FEKO software, such as to 3 cm and 5 cm, and the amplitude and phase difference before and after the microwave signal penetrated the target was obtained. The amplitude and phase difference were analyzed using Matlab software according to the aforementioned imaging detection algorithm to obtain the final imaging result. As can be seen from the figure, the device in this embodiment can detect the target and distinguish its size and orientation.

[0098] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A portable plate-type microwave imaging device, characterized in that: It includes a controller, an RF switch, and a detector; the controller is connected to the detector via the RF switch; The controller is configured with a display unit, an MCU module, a signal generator, and a mixer unit; the MCU module is used to generate, receive, calculate, and store signals; the display unit is connected to the MCU module and is equipped with a display screen and a human-machine interface; the signal generator is connected to both the MCU module and the mixer unit. The detector is equipped with a support and microwave antennas; the support has a U-shaped clamp structure, and multiple microwave antennas are evenly distributed on both sides of the clamp; the empty area between the two sides of the clamp is the detection area; The radio frequency switch is equipped with a switch switching module, which is used to switch the connection relationship of the microwave antenna sequentially or out of order; the connection relationship includes a first connection relationship and a second connection relationship. In the first connection relationship, at least one microwave antenna is connected to the transmitting end of the radio frequency switch, and the number of connected antennas is less than the number of microwave antennas on a single side plate. In the second connection relationship, the microwave antenna is connected to the receiving end of the radio frequency switch; The controller also integrates an analog-to-digital converter, which is connected to the receiver of the radio frequency switch.

2. The portable plate-type microwave imaging device according to claim 1, characterized in that: The main control chip of the MCU module is an embedded microcontroller chip; The signal generator is equipped with an radio frequency chip; The mixing unit is equipped with a mixer chip; The mixing unit is connected to the MCU module and the signal generator respectively.

3. The portable plate-type microwave imaging device according to claim 1, characterized in that: The microwave antenna array is distributed on both sides of the bracket; The number of microwave antennas on both sides of the bracket is the same and they are symmetrically distributed.

4. The portable plate-type microwave imaging device according to claim 3, characterized in that: The microwave antenna on one side of the bracket is an n×n planar array antenna, where n is a natural number and .

5. The portable plate-type microwave imaging device according to claim 4, characterized in that: The planar array antenna on one side of the bracket has at least m antenna mounting positions left in the middle, where m is a natural number. .

6. The portable plate-type microwave imaging device according to claim 1, characterized in that: The radio frequency switch also includes a power amplifier and a reflector bridge; The power amplifier is connected to the mixer unit and the reflection bridge, respectively. The reflective bridge is also connected to the controller and the switch switching module respectively; An amplitude and phase detection chip is also connected in series between the analog-to-digital converter and the receiving end of the radio frequency switch. The two input terminals of the amplitude and phase detection chip are respectively connected to the output terminal of the reflective bridge and the receiving terminal of the radio frequency switch; the output terminal of the amplitude and phase detection chip is connected to the analog-to-digital converter.

7. A portable plate-type microwave imaging method, characterized in that: Imaging using the portable plate-type microwave imaging device according to any one of claims 1-6, comprising the following steps: Adjust the portable plate-type microwave imaging device according to any one of claims 1-6 so that the target to be inspected is located in the detection area; The controller generates a transmission signal that is a mixture of high-frequency and low-frequency signals. The transmitted signal is sent sequentially or out of order to at least one microwave antenna via a switching module in a radio frequency switch. The microwave antenna in the non-transmitting state receives the feedback signal and transmits the feedback signal to the radio frequency switch; The feedback signal is mixed through multiple stages to obtain a mixed signal, and the mixed signal is converted into a mixed digital signal by an analog-to-digital converter. The MCU module processes the hybrid digital signal based on a delay-multiplication-superposition summation algorithm and obtains the processed signal; A heat map is drawn based on the processed signal, and the heat map is used as a target microwave imaging map.

8. The portable plate-type microwave imaging method according to claim 7, characterized in that: The MCU module in the controller generates a low-frequency signal with a frequency range of less than 30MHz. The controller contains a signal generator that produces high-frequency signals, with a frequency range of 30MHz-6GHz. The low-frequency signal and the high-frequency signal are mixed by a mixing unit to obtain the transmitted signal, and the signal frequency range is 10MHz-6GHz.

9. The portable plate-type microwave imaging method according to claim 8, characterized in that: The feedback signal is mixed through multiple stages of frequency mixing to obtain a mixed signal, including the following steps: The reference clock signal outputs the first local oscillator signal through a phase-locked loop; the reference clock signal outputs the second local oscillator signal through a clock generator. The transmitted signal is mixed with the first local oscillator signal to obtain a reference first mixed signal and a reflected first mixed signal, respectively. The reference first mixed signal is then mixed with the second local oscillator signal to obtain a reference second mixed signal. The feedback signal is mixed with the first local oscillator signal to obtain the received first mixed signal; The reflected first mixing signal and the received first mixing signal are filtered, and the filtering result is mixed with the second local oscillator signal to obtain the received second mixing signal; The feedback signal is compared with the transmitted signal in amplitude and phase to obtain amplitude-phase difference data; The mixed signal includes the reference second mixing signal, the received second mixing signal, and the amplitude-phase difference data; The hybrid digital signal processing based on the delayed multiplication and superposition algorithm includes the following steps: The amplitude of the hybrid digital signal is adjusted to obtain an equivalent signal; The equivalent signal is processed based on the autocorrelation function, and then the beamforming signal is obtained through beamforming operation. The processed signal is obtained by performing logarithmic and gamma transformations on the beamforming signal.

10. The portable plate-type microwave imaging method according to claim 9, characterized in that: The feedback signals are received in pairs, and the equivalent signal formula for the mixed digital signal is: ； In the formula, For each pair of received signals and The equivalent microwave signal.

Images