Portable plate-type microwave imaging device and method

Abstract

The invention provides a portable plate-type microwave imaging device and method. The portable plate-type microwave imaging device comprises a controller, a radio frequency switch and a detector, and the controller is connected with the detector through the radio frequency switch. Wherein the controller is provided with a display unit, an MCU module, a signal generator and a frequency mixing unit; the detector is provided with a bracket and a microwave antenna; the radio frequency switch is provided with a switch switching module, and the switch switching module is used for sequentially or disorderly switching the connection relation of the microwave antennas. The controller is also integrated with an analog-to-digital converter which is connected with the receiving end of the radio frequency switch. The device is simple in structure, low in cost, good in portability and easy to move; high-resolution imaging can be realized by combining multi-stage mixed signal processing, imaging is performed by relying on inverse scattering, and the microwave energy intensity is low, so that no heat effect is generated.

Description

Technical Field

[0001] The present invention relates to the technical field of general image data processing or generation, and particularly to a portable plate-type microwave imaging device and method. Background Art

[0002] Existing computed tomography (CT) and functional magnetic resonance imaging (fMRI) are generally large-scale devices, both of which are installed in specific institutions. Their equipment is complex to use, the detection process is lengthy, and the portability of the equipment is poor. Specifically: (1) The detection takes a long time. The time consumption includes, on the one hand, the time from discovering a problem to solving it. For example, since CT and fMRI are large in size and inconvenient to move, the detection needs to be carried out in a specific place, resulting in a long time for coming and going for detection; on the other hand, the detection process itself takes a long time. For example, the electrodes themselves need to be moistened and placed, resulting in a long detection time.

[0003] (2) The detection range is not extensive. For example, for volume impedance phase shift spectroscopy technology, the application scenarios are not extensive.

[0004] Therefore, the prior art research is on microwave detection imaging technology. Due to the characteristics of high frequency, short wavelength, and good directivity of microwaves, imaging can be performed by measuring the dielectric constant distribution of different objects through which they pass. However, there is a risk of secondary damage in the microwave detection imaging process. Therefore, in order to avoid the problem of multiple follow-up movements of the detection target, the devices of existing microwave detection methods are designed as annular structures. However, this structure is complex, which instead leads to inconvenient movement of the device, and even when performing full-angle detection, the target still needs to cooperate with the movement to complete the detection.

[0005] In summary, there is still a need to design a microwave detection imaging device with portability and boardability, and having advantages such as accurate scanning, wide application range, many resolution types, and low cost. Summary of the Invention

[0006] The present invention aims at the problems existing in the prior art, and provides a device with a simple structure and low cost, which can perform microwave detection imaging on a target, and realizes accurate imaging in combination with a specific method.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a portable plate-type microwave imaging device, mainly including a controller, a radio frequency switch, and a detector; the controller is connected to the detector through the radio frequency switch; The controller is configured with a display unit, an MCU module, a signal generator, and a mixing unit; the MCU module is used to generate signals, receive signals, calculate signals, and store signals; the display unit is connected to the MCU module, and the display unit is provided with a display screen and a human-machine interaction interface; the signal generator is respectively connected to the MCU module and the mixing unit; The detector is provided with a bracket and a microwave antenna; the bracket has a U-shaped splint structure, and a plurality of microwave antennas are evenly distributed on both sides of the splint; The RF switch is provided with a switch switching module, and the switch switching module is used to sequentially or disorderly switch the connection relationship of the microwave antennas; 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 RF switch, and the number of connected antennas is less than the number of microwave antennas on one side of the splint; In the second connection relationship, the microwave antenna is connected to the receiving end of the RF switch; The controller is also integrated with an analog-to-digital converter, and the analog-to-digital converter is connected to the receiving end of the RF switch.

[0008] Optionally, the main control chip of the MCU module is an embedded microcontroller chip; The signal generator is provided with a radio frequency chip; The mixing unit is provided with a mixer chip; The mixing unit is respectively connected to the MCU module and the signal generator.

[0009] Optionally, the microwave antenna array is distributed on both sides of the splint of the bracket; The number of microwave antennas on both sides of the splint of the bracket is the same and symmetrically distributed.

[0010] Optionally, the microwave antennas on one side of the splint of the bracket form an n×n planar array antenna, where n is a natural number and .

[0011] Optionally, at least m antenna installation positions are left empty in the middle of the planar array antenna on one side of the splint of the bracket, where m is a natural number and .

[0012] Optionally, the RF switch is also provided with a power amplifier and a reflection bridge; The power amplifier is respectively connected to the mixing unit and the reflection bridge; The reflection bridge is also respectively connected to the controller and the switch switching module; An amplitude-phase detection chip is also connected in series between the analog-to-digital converter and the receiving end of the RF switch; The two input ends of the amplitude-phase detection chip are respectively connected to the output end of the reflection bridge and the receiving end of the RF switch; the output end of the amplitude-phase detection chip is connected to the analog-to-digital converter.

[0013] On the other hand, the present invention also provides a portable plate-type microwave imaging method for imaging by the above portable plate-type microwave imaging device, which mainly includes the following steps: Adjust the above device so that the object to be detected is located in the detection area; The controller generates a transmission signal after mixing a high-frequency signal and a low-frequency signal; The transmission signal is sequentially or randomly sent to at least one microwave antenna through the switch switching module in the RF switch; the microwave antenna in the non-transmission state receives the feedback signal and transmits the feedback signal to the RF switch; The feedback signal obtains a mixed signal after multi-stage mixing, and the mixed signal is converted into a mixed digital signal through the analog-to-digital converter; The MCU module processes the mixed digital signal based on the delay multiplication superposition summation algorithm and obtains a processed signal; Draw a heat map based on the processed signal and use the heat map as the target microwave imaging map.

[0014] Optionally, the MCU module in the controller generates a low-frequency signal, and the signal frequency range is less than 30 MHz; The signal generator in the controller generates a high-frequency signal, and the signal frequency range is 30 MHz - 6 GHz; The low-frequency signal and the high-frequency signal are mixed through a mixing unit to obtain the transmission signal, and the signal frequency range is 10 MHz - 6 GHz.

[0015] Optionally, the feedback signal obtains a mixed signal after multi-stage mixing, including the following steps: The reference clock signal outputs a first local oscillator signal through the phase-locked loop; the reference clock signal outputs a second local oscillator signal through the clock generator; Mix the transmission signal with the first local oscillator signal to respectively obtain a reference first mixing signal and a reflection first mixing signal, and mix the reference first mixing signal with the second local oscillator signal to obtain a reference second mixing signal; Mix the feedback signal with the first local oscillator signal to obtain a received first mixing signal; perform signal screening on the reflection first mixing signal and the received first mixing signal, and mix the screening result with the second local oscillator signal to obtain a received second mixing signal; Perform amplitude-phase comparison between the feedback signal and the transmission signal 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; Processing the mixed digital signal based on the delay multiplication superposition summation algorithm includes the following steps: Adjust the amplitude of the mixed digital signal to obtain an equivalent signal; Process the equivalent signal based on the autocorrelation function, and then obtain a beamforming signal through beamforming operations; Obtain the processed signal by performing logarithmic transformation and gamma transformation on the beamforming signal.

[0016] Optionally, the feedback signals are received in pairs, and the equivalent signal formula of the mixed digital signal is: ; In the formula, is the equivalent microwave signal of each pair of received signals and

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention has a simple structure and low cost. The device adopts a plate antenna device design, reducing the volume of the equipment to make it portable. It can move quickly according to imaging requirements. It only needs to clamp the transceiver antenna board on both sides of the target to perform scanning imaging, without the risk of secondary injury; it transmits and receives through the microwave antenna on the splint, and combines multi-stage mixed signal processing to obtain high-resolution images; the reason is that there is an obvious difference in the total distance between the detection parts of the front cycle and the rear cycle from the antenna, so the characteristics of the target can also be accurately distinguished through microwave technology. Further, the microwave energy does not directly generate current, but forms a composite electromagnetic field path. This device relies on its inverse scattering for imaging, and the microwave energy intensity used is low and does not produce a thermal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 is a schematic diagram of the device in a specific embodiment of the present invention; Figure 2 is a schematic diagram of the signal flow in a specific embodiment of the present invention; Figure 3 is a schematic diagram of the circuit in a specific embodiment of the present invention; Figure 4It is the simulation result diagram of the 5 cm model in the specific embodiment of the present invention; Figure 5 It is the simulation result diagram of the 3 cm model in the specific embodiment of the present invention.

[0020] In the figure: 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. Specific embodiments

[0021] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0023] In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0024] In the present invention, unless otherwise clearly defined and limited, terms such as "installation" and "connection" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal connection of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] It is worth noting that the methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products unless otherwise specified, and their sources are not specifically limited.

[0026] On the one hand, as Figure 1As shown in the figure, this embodiment provides a portable plate-type microwave imaging device, which mainly includes a controller, a radio frequency switch, and a detector. Among them, the controller 17 is connected to the radio frequency switch 18 through a coaxial cable, and the radio frequency switch 18 is also connected to the detector through a coaxial cable.

[0027] The controller 17 is configured with a display unit, an MCU module, a signal generator, and a mixing unit. Optionally, the MCU module is used to generate signals, receive signals, calculate signals, and store signals. Therefore, in this embodiment, a microcontroller is selected as the MCU module. Its base is a multi-interface electronic circuit board, configured with a typical circuit of an STM32 minimum system board, and has various functional components such as a processor, a memory, and a timer. In this embodiment, the main control chip (processor) of the MCU module is an embedded microcontroller chip, and an STM32 chip is optional. The display unit is connected to the MCU module. The display unit is a color touch screen display, which is used to display the target microwave imaging and provide a man-machine interaction interface for the convenience of operators.

[0028] The signal generator is respectively connected to the MCU module and the mixing unit; optionally, the signal generator is provided with a radio frequency chip, preferably a MAX2871 chip.

[0029] The mixing unit is provided with a mixer chip; preferably an LTC5510 chip, and the mixing unit is respectively connected to the MCU module and the signal generator.

[0030] The detector is provided with a bracket and microwave antennas. As Figure 1 shown, the bracket is in an inverted U-shaped splint structure, and a plurality of microwave antennas are evenly distributed on both side splints; the two side splints are symmetrically arranged, and the cubic three-dimensional space enclosed between the two splints is the detection area. Considering portability, in this embodiment, the length range of the upper connecting cross plate of the U-shaped splint is designed to be 25 cm - 50 cm (matching the size of common detection targets), and a step-by-step strategy can be adopted. Multiple specifications of cross plates with lengths of 25, 30, 35, 40, 45, 50, and 55 cm are pre-produced for selection, and it is designed that the two side splints are connected to the upper connecting cross plate through a detachable connection structure, and the width range of the supporting plate is 15 cm - 25 cm; the overall plate thickness range of the U-shaped splint is 3 cm - 6 cm. Optionally, the microwave antenna array is distributed on the two side splints of the bracket, and the number of microwave antennas on the two side splints of the bracket is the same and symmetrically distributed with respect to the midline of the U-shaped splint, that is, a microwave antenna is provided on the lateral opposite side of each microwave antenna.

[0031] Furthermore, in combination with the above settings, the microwave antennas on the single-side splint of the bracket are in an n×n planar array antenna, where n is a natural number and . Specifically, for the convenience of understanding, in this embodiment, as Figure 1As shown, n is selected as 3, and thus 3×3 (a total of 9) mounting positions are evenly distributed on the inner surface of each side splint. Further, different from the full paving of the conventional design, the antenna arrangement in this embodiment is further optimized and improved based on the following factors, that is, a blanking design is carried out in the middle area without installing microwave antennas. The main factors are: Near-field effect influence: When multiple antennas are closely arranged, the near-field effect will change the radiation characteristics and impedance of the antennas, thereby affecting the performance of the antennas and signal transmission. Blanking in the middle can reduce the influence of the near-field effect, keep the antennas stable in their respective operating frequency bands, reduce interference with other antennas, and improve the stability and reliability of the entire antenna system.

[0032] Adapt to subsequent algorithms: The blanking layout in the middle is more conducive to the subsequent algorithms to process and analyze microwave signals. Moreover, blanking can make the microwave signals more evenly cover the detection area during propagation, avoiding the over-concentration or mutual cancellation of signals in some areas due to overly dense antennas. This can make better use of microwave signals and improve the imaging quality and detection effect.

[0033] Reduce the number of antennas: Reducing the number of antennas can reduce costs on the premise of meeting the effective detection coverage.

[0034] Closer to the head area: The human head is approximately spherical. The antenna array with blanking in the middle can avoid the problem of excessive microwave intensity in the middle area, so that the distance between the U-shaped splints can be designed smaller, and then the distance between the outer-ring microwave antennas and the head surface can be closer, reducing signal attenuation and reflection differences caused by inconsistent distances, and improving signal transmission efficiency and detection accuracy.

[0035] Therefore, at least m antenna mounting positions are blanked in the middle of the planar array antenna on the single-side splint of the bracket in this embodiment, where m is a natural number and , to meet the conditions of the detection area covered by the microwave antennas, and multiple regular (square areas, such as 1, , …… ) empty positions can be left in the middle. In this embodiment, n is taken as 3, so m takes the value of 1; therefore, the distribution rule of the microwave antennas is a checkerboard distribution with one empty position left in the middle, such as Figure 1As shown, there are 8 microwave antennas successively distributed on the clamping plate on the left, namely 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, microwave antenna 8#8 (microwave antenna z#z represents the z-th microwave antenna, and the reference numeral is z). Similarly, there are also 8 microwave antennas successively distributed on the clamping plate on the right, namely 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, microwave antenna 16#16.

[0036] A total of 16 microwave antennas are all connected to the RF switch 18 through coaxial cables. The RF switch 18 is provided with a switch switching module, and the switch switching module is a switch switching circuit for sequentially or randomly switching the connection relationships of the microwave antennas; the connection relationships are provided with a first connection relationship and a second connection relationship.

[0037] Among them, in the first connection relationship, in this embodiment, a microwave antenna is connected to the transmitting end of the RF switch in a preset order; in the second connection relationship, the other non-transmitting state microwave antennas are connected to the receiving end of the RF switch.

[0038] Optionally, as shown in Figure 2 and Figure 3 , a power amplifier (PA block) and a reflection bridge are also provided in the RF switch 18; among them, the power amplifier is respectively connected to the mixing unit and the reflection bridge, and an adjustable attenuator RFSA3714 is connected in series in front of the power amplification device PA to play a role in adjusting the signal power; the reflection bridge is also respectively connected to the controller and the switch switching module (switch transmitting). The controller 17 in this embodiment integrates a reference clock, whose clock frequency is 27 MHz, and provides clock signals (PLL reference) for multiple phase-locked loops PLL to generate various required reference signals, that is, local oscillator signals. Among them, the phase-locked loops include phase-locked loop PLL1 (clock generator with integrated circuit model SI5351), phase-locked loop PLLA (integrated circuit model MAX2871), and phase-locked loop PLLB (integrated circuit model MAX2871). The phase-locked loop PLL1 and the phase-locked loop PLLA respectively provide a low-frequency reference signal (<30 MHz) and a high-frequency reference signal (30 MHz - 6 GHz), and screen them through a 1-of-2 selection circuit (an analog switch constructed by CMOS devices in this embodiment), and provide the selected signals to the adjustable attenuator for preprocessing the mixed signal. A 1-to-2 power divider is also connected in series after the power amplifier, that is, a circuit for realizing signal distribution, and the two divided paths are respectively connected to the reflection bridge and a mixer (X) connected to an output end of the phase-locked loop PLLB.

[0039] The controller 17 is also integrated with an analog-to-digital converter for power detection and ADC acquisition. The analog-to-digital converter is connected to the receiving end of the RF switch, and an amplitude-phase detection chip (model AD8302) is connected in series between the analog-to-digital converter and the receiving end of the RF switch. The two input ends of the amplitude-phase detection chip are respectively connected to the output end of the reflection bridge and the receiving end of the RF switch; among them, the reflection bridge in this embodiment is provided with two output ends, one output end is divided into two paths through a 1-to-2 power divider and is respectively connected to the transmitting end, that is, port 1 (P1: transmitting, reflecting) and the amplitude-phase difference reference end of the amplitude-phase detection chip; the other output end is connected to the mixer (X) connected to an output end of the phase-locked loop PLLB. The output end of the amplitude-phase detection chip is connected to the analog-to-digital converter.

[0040] The analog-to-digital converter is also connected to the reflection bridge for collecting the transmitted signal as one of the reference signals. The connection structure is specifically as follows: the receiving end of the RF switch, that is, port 2 (P2: receiving) is connected to a two-stage 1-of-2 circuit composed of a direct connection channel and a low-noise amplifier (LNA), and is connected to the mixer (X) connected to an output end of the phase-locked loop PLLB, and then is connected to the reflection bridge and the phase-locked loop PLLB hybrid circuit and outputs to the receiving channel through 1-of-2; the receiving channel is connected to the PGA programmable amplifier through the mixer (X) of the output line of the phase-locked loop PLL1, and then is connected to the digital-to-analog converter. Among them, the phase-locked loop PLL1 also has an output line connected to the mixer (X) connected to the phase-locked loop PLLB and the reflection bridge through another mixer (X) and is connected to the digital-to-analog converter as an ADC drive reference signal of the digital-to-analog converter.

[0041] In this embodiment, based on the foregoing device, a portable plate-type microwave imaging method is also provided, which mainly includes the following steps: First, invert the foregoing device and adjust it so that the target is located in the detection area. It can be understood that after the position and posture of the target to be detected are determined appropriately, there is no need to move it anymore, and only the position of the device needs to be adjusted. The device can be placed flat or suspended by a multi-axis hanging bracket.

[0042] The MCU module in the controller 17 generates a low-frequency signal with a range less than 30 MHz; the MCU module also controls the signal generator to generate a high-frequency signal with a range of 30 MHz - 6 GHz; the two signals are mixed by the subsequent connected mixing unit to mix the high-frequency signal and the low-frequency signal and obtain a transmitted signal with a frequency range of 10 MHz - 6 GHz.

[0043] The transmitted signal enters the RF switch, passes through the power amplifier and the reflection bridge, and then enters the transmitting end. The switch switching module sequentially connects each microwave antenna, and the sequential connection means connecting the microwave antenna 1# - microwave antenna 16# in sequence at fixed time intervals. During this period, when each microwave antenna is not in the transmitting state, it is connected to the receiving end by the switch switching module and serves as a microwave receiver. In this embodiment, in order to simplify the switch switching module, it is designed that only all the microwave antennas on the opposite side are connected to the receiving end during the switching process. For example, when the microwave antenna 1# transmits, the microwave antennas 9# - microwave antenna 16# are connected to the receiving end, while the microwave antennas 2# - microwave antenna 8# do not participate in the operation.

[0044] The feedback signal of the microwave received by the receiving end is mixed through multiple stages to obtain a mixed signal, and the mixed signal is converted into a mixed digital signal through an analog-to-digital converter. Among them, the steps for obtaining the mixed signal after the feedback signal is mixed through multiple stages are as follows: Reference Figure 3 As shown, the transmitted signal after the power divider divides 1 into 2 is used as a reference and mixed with the first local oscillator signal of the phase-locked loop PLLB to obtain a reference first mixed frequency signal; the signal of the reflection bridge is mixed with the first local oscillator signal of the phase-locked loop PLLB to obtain a reflection first mixed frequency signal; the reference first mixed frequency signal is mixed with the second local oscillator signal of the phase-locked loop PLL1 to obtain a reference second mixed frequency signal; The feedback signal continuously performs a 1-in-2 selection operation through the LNA low-noise amplifier, and then is divided into two paths. One path is mixed with the first local oscillator signal to obtain a received first mixed frequency signal, and signal screening is performed on the reflection first mixed frequency signal and the received first mixed frequency signal. Among them, when the reflection first mixed frequency is selected, a certain type of coefficient in the microwave propagation coefficient is obtained, and when the received first mixed frequency is selected, another type of coefficient is obtained; then, the above screening result is mixed with the second local oscillator signal to obtain a received second mixed frequency signal; the other path is compared in amplitude and phase with the transmitted signal to obtain amplitude and phase difference data; Thus, the mixed signal includes a reference second mixed frequency signal, a received second mixed frequency signal, and amplitude and phase difference data.

[0045] The MCU module processes the mixed digital signal based on the delay multiplication superposition summation algorithm and obtains a processed signal; among them, the steps for processing the mixed digital signal based on the delay multiplication superposition summation algorithm are as follows: Among them, the reference second mixing is the transmitted signal x, and the received second mixing 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 switch switching module of the device, only 8 antennas receive the same transmitted signal, which is the transmitted microwave signal, which is the received signal after experiencing Take the square root after taking the absolute value to obtain an equivalent microwave signal with the same dimension after scaling , and the formula is: ; Process the equivalent signal based on the autocorrelation function, and then obtain the beamforming signal through beamforming operation. Among them, the autocorrelation function obtains the beamforming signal The formula is: ; Finally, envelope detection can be performed on the beam signal. The envelope information can be extracted through the envelope function in Matlab. The processed signal is obtained by performing logarithmic transformation and gamma transformation on the beamforming signal. Logarithmic transformation refers to performing a log operation on the original signal, and gamma transformation refers to performing an exponential operation on the original signal. Envelope detection is used to draw the curves of the amplitudes of the transmitted signal and the received signal changing with time. By comparing the differences in their envelopes, the amplitude difference and phase difference between the transmitted signal and the received signal can be calculated, and they are used to compare or correct the aforementioned amplitude-phase difference data.

[0046] Based on the processed signal, draw a heat map. Divide the space between the antennas into finite elements of 1mm×1mm×1mm. Calculate the signal intensity on each finite element according to the processed signal and its delay above. Different intensity mappings correspond to the color values in the heat map, and the heat map is used as the target microwave imaging map. Among them, using the aforementioned amplitude-phase difference data, the signal time delay can be obtained by calculating the phase difference; the signal attenuation can be obtained by calculating the amplitude difference, and then by aligning and canceling the time delay, the intensity after superimposing different attenuation signals can be obtained, and this intensity is used to map the corresponding color value in the heat map.

[0047] Based on the above method, use the FEKO three-dimensional full-wave electromagnetic simulation software for simulation, and the results are as shown in Figure 4 、 5 . Perform simulation tests with FMCW waves of 1.8GHz. Adjust the size of the target to be measured in the FEKO software, such as 3cm and 5cm, and scan to obtain the amplitude-phase difference before and after the microwave signal penetrates the target. Use Matlab software to analyze the amplitude-phase difference according to the above 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 to be measured and can distinguish the size and orientation of the target to be measured.

[0048] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than a limitation on the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art does 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, a radio frequency switch and a detector; the controller is connected to the detector through the radio frequency switch; The controller is configured with a display unit, an MCU module, a signal generator and a mixing unit; the MCU module is used to generate signals, receive signals, calculate signals and store signals; the display unit is connected to the MCU module, and the display unit is provided with a display screen and a human-computer interaction interface; the signal generator is respectively connected to the MCU module and the mixing unit; The detector is provided with a bracket and a microwave antenna; the bracket is a U-shaped clamping plate structure, and multiple microwave antennas are evenly distributed on the clamping plates on both sides; the empty area between the clamping plates on both sides is the detection area; The radio frequency switch is provided with a switch switching module, and the switch switching module is used to switch the connection relationship of the microwave antenna in sequence or disorderly; the connection relationship is provided with 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 microwave antennas is less than the number of microwave antennas on the single-side clamping plate; In the second connection relationship, the microwave antenna is connected to the receiving end of the radio frequency switch; The controller is also integrated with an analog-to-digital converter, and the analog-to-digital converter is connected to the receiving end 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 provided with a radio frequency chip; The frequency mixing unit is provided with a mixer chip; The frequency 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 the two side clamping plates of the bracket; The number of microwave antennas on the clamping plates 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 the single side clamping plate 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: At least m antenna installation positions are left empty in the middle of the planar array antenna on the single-side clamping plate of the bracket, where m is a natural number and .

6. The portable plate-type microwave imaging device according to claim 1, characterized in that: The radio frequency switch is also provided with a power amplifier and a reflection bridge; The power amplifier is connected to the frequency mixing unit and the reflection bridge respectively; The reflective bridge is also connected to the controller and the switch 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 ends of the amplitude and phase detection chip are respectively connected to the output end of the reflection bridge and the receiving end of the radio frequency switch; the output end 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: The portable plate-type microwave imaging device for imaging according to any one of claims 1 to 6 comprises the following steps: Adjusting the portable plate-type microwave imaging device according to any one of claims 1 to 6 so that the target to be inspected is located in the inspection area; The controller generates a transmission signal which is a mixture of a high frequency signal and a low frequency signal; The transmission signal is sent to at least one microwave antenna in sequence or disorderly through a switch switching module in a radio frequency switch; The microwave antenna in a non-transmitting state receives the feedback signal and transmits the feedback signal to the radio frequency switch; The feedback signal is subjected to multi-stage mixing to obtain a mixed signal, and the mixed signal is converted into a mixed digital signal through an analog-to-digital converter; The MCU module processes the mixed digital signal based on a delayed multiplication and addition algorithm to obtain a processed signal; A thermal map is drawn based on the processed signal, and the thermal 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, and the signal frequency range is less than 30MHz; The signal generator in the controller generates a high-frequency signal, and the signal frequency range is 30MHz-6GHz; The low-frequency signal and the high-frequency signal are mixed by a frequency mixing unit to obtain the transmission signal, and the signal frequency range is 10 MHz-6 GHz.

9. The portable plate-type microwave imaging method according to claim 8, characterized in that: The feedback signal is subjected to multi-stage mixing to obtain a mixed signal, comprising the following steps: The reference clock signal outputs a first local oscillator signal through a phase-locked loop; the reference clock signal outputs a second local oscillator signal through a clock generator; The transmit signal is mixed with the first local oscillator signal to obtain a reference first mixing signal and a reflected first mixing signal respectively, and the reference first mixing signal is mixed with the second local oscillator signal to obtain a reference second mixing signal; Mixing the feedback signal with the first local oscillator signal to obtain a received first mixed signal; Performing signal screening on the reflected first mixing signal and the received first mixing signal, and mixing the screening result with the second local oscillator signal to obtain a received second mixing signal; Comparing the feedback signal with the transmitted signal in amplitude and phase to obtain amplitude and phase difference data; The mixed signal includes the reference second mixed signal, the received second mixed signal and the amplitude and phase difference data; The mixed digital signal processing based on the delayed multiplication and addition algorithm includes the following steps: Performing amplitude adjustment on the mixed digital signal to obtain an equivalent signal; Processing the equivalent signal based on the autocorrelation function, and then obtaining a beamforming signal through a beamforming operation; The processed signal is obtained by performing logarithmic transformation and gamma transformation 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 of the mixed digital signal is: ； In the formula, For each pair of received signals and The equivalent microwave signal.

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