A portable multi-channel passive millimeter wave radiation detector system

Abstract

The present invention discloses a portable multi-channel passive millimeter wave radiation detector system, which includes: a metal shell; a focusing lens antenna fixedly arranged at one end of the metal shell, the focusing lens antenna adopts a metasurface lens antenna; a feed antenna arranged opposite to the focusing lens antenna is arranged inside the metal shell, the feed antenna is connected to a radiometer receiver, the feed antenna adopts a conjugate linear gradient slot antenna with metamaterial units loaded on both sides, and is arranged in a two-dimensional N×N manner on the focal plane, N≥2; the electromagnetic waves radiated by the target scene to be measured are gathered to the feed antenna through the focusing lens antenna and received, and transmitted to the radiometer receiver; the voltage data output by the radiometer receiver is processed by a processing module to generate a target scene image, and is displayed. The overall size of the measuring instrument system is reduced, so that the detector system can be portable; the feed antenna array is arranged in a two-dimensional N×N manner, which improves the imaging speed and imaging quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of millimeter wave detection, and more specifically, relates to a portable multi-channel passive millimeter wave radiation detector system. Background Art

[0002] Millimeter waves refer to electromagnetic waves with wavelengths between 1mm and 10mm. Passive millimeter wave imaging systems form images by passively detecting naturally occurring thermal radiation energy from target scenes.

[0003] At present, focal plane imaging systems are widely used in the field of passive millimeter wave detection. The focal plane imaging system consists of a focusing antenna and a feed antenna. The focusing antenna of a traditional passive focal plane imaging system mostly uses a reflector antenna. The caliber and size of the reflector antenna are often large, and there is a feed shielding effect. The feed antenna mostly uses a horn antenna, which is large in size. There are constraints in the design of the array arrangement, and the processing cycle is long and the cost is high, making it difficult to promote it widely. The arrangement of the focal plane array is single, which affects the coverage field of the focal plane imaging system and slows the imaging speed.

[0004] Traditional focal plane imaging systems have some problems. For example, the system size is too large and requires the use of mechanical equipment such as a turntable and cannot be operated handheld. The small number of channels leads to slow imaging speed, low imaging resolution, and high system processing costs. Summary of the invention

[0005] In view of the defects of the related art, the purpose of the present invention is to provide a portable multi-channel passive millimeter-wave radiation detector system, aiming to solve the problems that the focusing antenna and the feed antenna are large in size, and there are constraints in the design of the array arrangement, which result in the imaging system being large in size, not portable, slow in imaging speed, low in imaging resolution and high in cost.

[0006] To achieve the above-mentioned object, the present invention provides a portable passive millimeter wave radiation detector system, comprising: a metal housing;

[0007] A focusing lens antenna fixedly arranged at one end of the metal shell, wherein the focusing lens antenna adopts a super-surface lens antenna;

[0008] A feed antenna arranged opposite to the focusing lens antenna is arranged inside the metal shell, and the feed antenna is connected to the radiometer receiver. The feed antenna adopts a conjugate linear gradient slot antenna with metamaterial units loaded on both sides, and is arranged in a two-dimensional N×N manner on the focal plane, where N≥2; the electromagnetic waves radiated by the target scene to be measured are gathered by the focusing lens antenna to the feed antenna and received, and transmitted to the radiometer receiver;

[0009] The voltage data output by the radiometer receiver is processed by the processing module to generate a target scene image, which is then displayed.

[0010] Optionally, the metasurface lens antenna is composed of three different metasurface units, and the metal layer structures of the three metasurface units are different; the aperture field of the metasurface unit is square, and the three metasurface units all include M+1 metal layers and M dielectric substrates arranged at intervals, and a metal inner circle is arranged at the center of each metal layer.

[0011] Beneficial effects: The metasurface lens has the characteristics of light weight, small size, low loss, good focusing effect, etc., which is conducive to the portable use of the equipment.

[0012] Optionally, the phase and amplitude of the transmitted electromagnetic wave are regulated by changing the metal inner circle radius of the metal layer of the metasurface unit.

[0013] Optionally, the phase of the metasurface lens antenna is designed by n bit discretization, dividing the 360° phase into two equal parts. n discrete phase values, according to the formula The phase value required for each position is calculated; where the lens center position coordinate is (0,0), (x, y) is the unit position coordinate in the metasurface lens, and λ 0 is the wavelength in free space, f is the focal length of the metasurface lens, is the reference phase of the central unit of the metasurface lens;

[0014] The metasurface unit with the highest transmittance among the three metasurface units corresponding to each discrete phase value is selected as the target metasurface unit corresponding to this discrete phase value; the phase value calculated according to each target position is compared with 2 n The target metasurface unit corresponding to the closest discrete phase value is selected and set at the target position to form a metasurface lens antenna.

[0015] Beneficial effects: The metasurface unit structure can control the phase and amplitude of the transmitted electromagnetic wave by changing the radius of the metal inner circle. It has the characteristics of wide bandwidth, polarization insensitivity and incident angle insensitivity, and can achieve 360° phase response characteristics.

[0016] Optionally, the metamaterial unit includes a three-layer structure, which is a dielectric substrate and a first metal layer and a second metal layer plated on both sides of the dielectric substrate.

[0017] Beneficial effects: The conjugate linear gradient slot antenna loaded with the metamaterial unit has the advantages of high gain, low sidelobe level, low return loss, low cost, easy processing, light weight, compact size, narrow beam width and relatively wide operating frequency band.

[0018] Optionally, the first metal layer comprises two metal square rings with opposite opening directions, the second metal layer is a long strip structure, and the two metal square rings form a "U"-shaped structure; the first metal layer and the second metal layer are both copper-plated.

[0019] Optionally, two rows of metallized through holes are provided on the radiating arm of the conjugate linear tapered slot antenna, and periodic rectangular slots are etched above the radiating arm.

[0020] Beneficial effects: Two rows of metallized through holes are added to extend the metallized through holes of SIW (substrate integrated waveguide) further toward the antenna radiation unit; the periodic rectangular gaps make the aperture field distribution more uniform.

[0021] Optionally, the feed antennas are arranged closely in sequence in the transverse direction, and the distance between adjacent feed antennas in the longitudinal direction is 15 mm.

[0022] Beneficial effects: The feed antenna array is compactly arranged, covers a large field of view, has a small empty area, and has a large number of arrays, so the radiation information of the target scene can be obtained more quickly during scanning.

[0023] Optionally, the radiometer receiver is arranged corresponding to the feed antenna, and the radiometer receiver is connected to the feed antenna in a one-to-one correspondence;

[0024] The radiometer receiver adopts a direct detection receiver.

[0025] Beneficial effects: Multi-channel acquisition of radiation information of the target scene; the use of a direct detection structure, without the need for a local oscillator and mixer, greatly reducing size and cost.

[0026] Optionally, the processing module includes: a data acquisition and signal conditioning module connected to the radiometer receiver, the data acquisition and signal conditioning module is connected to the image processing module and the main control module, and the main control module is also connected to the image processing module, the display module and the data storage module; the data acquisition and signal conditioning module and the image processing module are used to process the data received by the radiometer receiver and generate target scene image data; the display module is used to display the target scene image, and the main control module is used to control each module;

[0027] A power module is also provided inside the metal shell to connect the modules and supply power to the modules;

[0028] The metal shell is also provided with a handheld handle, a button and an angle sensor, and the button and the angle sensor are both connected to the main control module;

[0029] The angle sensor is used to record the corresponding relationship between the output voltage of the radiometer receiver and the detector posture, and transmit it to the image processing module through the main control module to correct the obtained data;

[0030] The main control module adopts a microprocessor, and the main control module is used to control each module according to the operation of the button.

[0031] Beneficial effects: The microcontroller reduces the size of the instrument; the receiver has a gear adjustment function and can detect a wide range of radiation brightness temperatures; the angle sensor is used to correct the scanned image to improve the image quality.

[0032] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0033] The technical solution of the present invention proposes a portable multi-channel passive millimeter wave radiation detector system, wherein a focusing lens antenna adopts a metasurface lens antenna, and a feed antenna adopts a conjugate linear gradient slot antenna loaded with metamaterial units on both sides. The metasurface lens has the advantages of light weight, small size, and good focusing effect, and the conjugate linear gradient slot antenna loaded with metamaterial units has the advantages of high gain, low sidelobe level, light weight, and compact size, which effectively reduces the size of the imaging system and the manufacturing cost, so that the detector system can be portable. The feed antenna is arranged in a two-dimensional N×N manner on the focal plane, N≥2, the array is compactly arranged, the coverage field is large, the coupling effect is low, the imaging resolution is high, and the imaging speed and imaging quality are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a portable multi-channel passive millimeter wave radiation detector system provided by an embodiment of the present invention;

[0035] Figure 2 is a schematic top view of a metasurface lens of a portable multi-channel passive millimeter wave radiation detector system provided by an embodiment of the present invention;

[0036] Figure 3 It is a schematic diagram of the first metasurface unit structure for a metasurface lens antenna provided by an embodiment of the present invention;

[0037] Figure 4 is a schematic diagram of a second metasurface unit structure for a metasurface lens antenna provided by an embodiment of the present invention;

[0038] Figure 5 is a schematic diagram of a third metasurface unit structure for a metasurface lens antenna provided in an embodiment of the present invention;

[0039] Fig. 6AIt is a structural schematic diagram of a feed antenna of a portable multi-channel passive millimeter wave radiation detector system provided by an embodiment of the present invention;

[0040] Figure 6B Schematic diagram of the structure of a metamaterial unit for a feed antenna provided by an embodiment of the present invention

[0041] Figure 6C is a structural schematic diagram of another feed antenna provided by an embodiment of the present invention;

[0042] Figure 7 It is a schematic diagram of the arrangement of the feed antenna provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] The contents involved in the above embodiment are described below in conjunction with a preferred embodiment.

[0045] like Figure 1 As shown, a portable passive millimeter wave radiation detector system comprises: a metal shell 1 and a handheld handle 2 fixed on the metal shell 1; a focusing lens antenna 3, a feed antenna 4, a radiometer receiver 5, a data acquisition and signal conditioning module 6, an image processing module 7, a main control module 8, a display module 9, a data storage module 10 and a power supply module 11 arranged inside the metal shell 1;

[0046] The focusing lens antenna 3 is fixedly arranged at one end of the metal housing 1, and the focusing lens antenna 3 adopts a super surface lens antenna;

[0047] A feed antenna 4 is arranged inside the metal housing 1 and is arranged opposite to the focusing lens antenna 3. The feed antenna 4 is connected to the radiometer receiver 5. The feed antenna 4 adopts a conjugate linear gradient slot antenna loaded with a metamaterial unit and is arranged in a two-dimensional N×N manner on the focal plane, where N≥2. The electromagnetic waves radiated by the target scene to be measured are gathered to the feed antenna 4 through the focusing lens antenna 3 and received, and then transmitted to the radiometer receiver 5.

[0048] The voltage data output by the radiometer receiver 5 is processed by the processing module to generate a target scene image, which is then displayed.

[0049] The processing module includes: a data acquisition and signal conditioning module 6 , an image processing module 7 , a main control module 8 , a display module 9 and a data storage module 10 .

[0050] The radiometer receiver 5 is connected to the data acquisition and signal conditioning module 6, the data acquisition and signal conditioning module 6 is connected to the image processing module 7 and the main control module 8, and the main control module 8 is also connected to the image processing module 7, the display module 9 and the data storage module 10; the data acquisition and signal conditioning module 6 and the image processing module 7 are used to process the voltage data output by the radiometer receiver 5 and generate a target scene image; the display module 9 is used to display the target scene image, and the main control module 8 is used to regulate each module; the power supply module 11 is connected to each module and is used to supply power to each module.

[0051] The metal shell 1 of the portable passive millimeter wave radiation detector system is cylindrical, with a focusing lens antenna 3 using a metasurface lens antenna fixed at one end, the center of the focal plane feed antenna 4 array fixed inside is located at the focus of the focusing lens antenna 3, and a display module 9 is fixed on the outside of the other end. A handheld handle 2 is fixed on the top of the metal shell 1, which can be held by one person for scanning imaging.

[0052] like Figure 2-Figure 5 As shown, optionally, the metasurface lens antenna 3 is composed of three different metasurface units 31, and the metal layer structures of the three metasurface units 31 are different; the three metasurface units 31 all include M+1 metal layers and M dielectric substrates arranged at intervals, and a metal inner circle is arranged at the center of each metal layer.

[0053] The material of the metal layer is copper, and the material model of the dielectric substrate is RT / duroid 5880.

[0054] The metasurface lens antenna 3 is obtained by combining three different stacked circular ring structures. Figure 2 As shown, the metasurface lens antenna 3 is composed of a plurality of three types of metasurface units 31 arranged compactly. Among them, the ring structure has been proven to help the structural unit achieve the requirements of polarization insensitivity and incident angle insensitivity, and the stacked structure with a locally induced resonant mode can not only expand the bandwidth but also help to enhance the transmission efficiency of the structural unit.

[0055] The three metasurface units all contain M+1 identical metal layers A and M identical dielectric substrates B. The metal material is copper with a copper plating thickness of 0.035 mm, and the material model of the dielectric substrate is RT / duroid 5880 with a thickness of 0.508 mm.

[0056] The metasurface unit can be composed of at least 2 metal layers and 1 dielectric substrate layer. In this embodiment, the range of phase coverage can be expanded by increasing the number of metasurface layers. After simulation, a structure of 4 metal layers and 3 dielectric substrate layers is selected to meet 360° phase coverage.

[0057] Optionally, the aperture field of the metasurface unit is square, and the phase and amplitude of the transmitted electromagnetic wave are controlled by changing the metal inner circle radius of the metal layer of the metasurface unit.

[0058] like Figure 3 The figure shows the schematic diagram of the first metasurface unit structure. The aperture field of the first metasurface unit is square with a side length of 3.2 mm. The metal layer includes a square ring a1, a circular ring a2 and an inner circle R. The aperture size of the square ring a1 and the diameter of the circular ring a2 are both 3.2 mm. The widths of the square ring a1 and the circular ring a2 are both 0.1 mm. The radius of the metal inner circle R is smaller than that of the circular ring a2. By changing the radius of the metal inner circle R, the phase and amplitude of the transmitted electromagnetic wave can be controlled. The radius of the metal inner circle R varies from 0.4 to 1.45 mm. The copper plating thickness is 0.035 mm. The material model of the dielectric substrate B is RT / duroid 5880 with a thickness of 0.508 mm.

[0059] like Figure 4 The figure shows the schematic diagram of the second metasurface unit structure. The aperture field of the second metasurface unit is square with a side length of 3.2mm. The metal layer includes a square ring a1 and an inner circle R. The diameter of the square ring a1 is 3.2mm and the width is 0.1mm. The phase and amplitude of the transmitted electromagnetic wave are controlled by changing the radius of the metal inner circle R. The radius of the metal inner circle R varies from 0.4 to 1.45mm. The copper plating thickness is 0.035mm. The material model of the dielectric substrate B is RT / duroid 5880 with a thickness of 0.508mm.

[0060] like Figure 5 The figure shows the schematic diagram of the structure of the third metasurface unit. The aperture field of the third metasurface unit is square with a side length of 3.2mm. The metal layer is the first part c generated by the hollowed-out circle embedded in the square metal plate. The side length of the square metal plate and the diameter of the embedded circle are both 3.2mm. The metal layer also includes the second part of the metal inner circle R. By changing the radius of the metal inner circle R, the phase and amplitude of the transmitted electromagnetic wave can be controlled. The radius of the metal inner circle R varies from 0.4 to 1.45mm. The copper plating thickness is 0.035mm, and the material model of the dielectric substrate is RT / duroid 5880 with a thickness of 0.508mm.

[0061] The above three types of metasurface units all have the characteristics of broadband, polarization insensitivity and incident angle insensitivity. Metasurface lenses have the characteristics of light weight, small size, low loss and good focusing effect, which is conducive to the portable use of equipment.

[0062] The focusing lens antenna 3 adopts a metasurface lens antenna. In this embodiment, the spatial resolution of the imaging system depends on the 3dB beam width of the antenna. Usually, the 3dB beam width of the focal plane antenna is approximately θ3dB =1.22λ 0 / D, where D is the size of the lens antenna, λ 0 is the working wavelength, where λ 0 is the wavelength corresponding to 35GHz. Assuming that the spatial resolution of the detector is set to less than 4°, it can be calculated that the minimum exit diameter D should be 130mm. Taking into account the 3dB beam width and aperture size, the aperture of the metasurface lens antenna is set to 144mm, and the repetition period P of the metasurface unit is 3.2mm. By calculation, the metasurface lens antenna needs to be composed of 1597 metasurface units.

[0063] When the size of the metasurface lens is constant, the larger the focal length, the smoother the phase change that needs to be compensated on the metasurface lens antenna, but the cross-section of the lens antenna increases; the smaller the focal length, the sharper the phase change that needs to be compensated, but the cross-section of the lens antenna decreases. In order to optimize the imaging effect as much as possible, the focal diameter ratio f / D of the lens antenna is selected to be 1, that is, the focal length of the metasurface lens antenna is set to 144mm.

[0064] The basic principle of the metasurface lens antenna is the same as that of the dielectric lens antenna, but the metasurface lens antenna achieves different phases through metasurface units to meet the phase compensation requirements. When designing the metasurface focusing lens antenna of the detector system, unless otherwise specified, the metasurface lens is located in the plane of z=0, with its center at the coordinate (0, 0, 0), and the polarization direction of the simulated incident plane wave is along the x-axis. According to the working principle of the metasurface lens antenna, the plane wave is incident toward the +Z axis, and after being focused by the metasurface lens, it converges to the focal point F. In order for the metasurface lens to achieve the focusing effect, its phase distribution needs to meet Where (x, y) is the position coordinate of the unit in the metasurface lens in the xoy plane; 0 is the wavelength in free space, and the wavelength corresponding to the working center frequency of 35 GHz is used in the design; f is the focal length of the metasurface lens, which is determined to be 144 mm; is the reference phase of the center unit of the metasurface lens, and its value is the phase of the unit at the center position of the metasurface lens.

[0065] The ideal metasurface lens phase compensation is to change continuously within the range of 0-360°. However, since it is difficult for the structural unit to provide all the calculated phase values, the phase of the metasurface lens is discretized. Optionally, an n-bit discrete design is used in the design, that is, the 360° phase is divided into 2 n Divide equally, select 2 n Each structural unit covers a 360° phase.

[0066] In this embodiment, the phase of the metasurface lens antenna adopts a 4-bit discretization design, and the 360° phase is equally divided into 16 discrete phase values, and the metasurface structure units with the highest transmittance corresponding to the 16 discrete phase values ​​are selected.

[0067] The metasurface lens antenna used in this embodiment contains a total of 1597 metasurface unit structures. The metasurface lens antenna is designed by combining three types of metasurface units. Since the three types of metasurface units can all achieve the required phase, the phase value calculated for each target position is compared with the 16 discrete phase values, and the closest discrete phase value is selected as the required phase value of the target position, and then the metal inner circle radius R of the three types of metasurface units at the discrete phase value is obtained, and the metasurface structure unit with the highest transmittance is screened out to finally form a metasurface lens antenna. The metasurface unit structure can achieve phase and amplitude control of the transmitted electromagnetic wave by changing the metal inner circle radius, and has the characteristics of satisfying wideband characteristics, polarization insensitivity and incident angle insensitivity, and can achieve 360° phase response characteristics.

[0068] The central unit of the metasurface lens antenna is selected as the third metasurface unit structure with an inner radius R of 1.19 mm, a phase of 180°, and a transmission amplitude of 0.99, which can ensure that the central transmission amplitude of the metasurface lens is high and reduce transmission loss. The phase of the unit structure at the center position is determined, that is, The phases that need to be satisfied at other positions (x′, y′) can be calculated according to the formula Calculated. Since the three metasurface unit structures can all achieve the required phase, when selecting the unit structure corresponding to each phase value, the structure with the highest corresponding transmittance among the three structures is used as the target metasurface unit for this phase value. Then, according to the phase value that needs to be met at each position, the corresponding target metasurface units are arranged to form a metasurface lens antenna composed of a combination of multiple metasurface unit structures.

[0069] In this embodiment, the designed metasurface lens antenna has an aperture of 144mm, an overall thickness of 1.664mm, and a focal length of 144mm; the metasurface lens has the advantages of light weight, small size, low loss, and good focusing effect, which is conducive to reducing the size of the detector system and facilitating portable use of the equipment.

[0070] like Fig. 6AAs shown, the feed antenna 4 adopts a conjugate linear gradient slot antenna with metamaterial units 41 periodically loaded on both sides, and the operating frequency band is 33-37GHz. The feed antenna 4 includes a dielectric substrate, a metal layer plated on both sides of the dielectric substrate, and metamaterial units (41a and 41b) loaded on the left and right sides of the dielectric substrate. The metal material is copper, and the copper plating thickness is 17.5um. The material model of the dielectric substrate is Rogers6002, and its thickness is 0.508mm. The metal layer structure on the front and back sides of the antenna is the same, symmetrical about the center of the dielectric substrate, forming a conjugate structure.

[0071] The metamaterial unit 41 is a left-handed material of a SRR / Wire structure, which has electromagnetic properties of negative magnetic permeability and negative dielectric constant. The unit behaves as a negative magnetic permeability material in 32-34 GHz and as a negative dielectric constant material in 34-36 GHz.

[0072] like Figure 6B As shown, optionally, the metamaterial unit includes a three-layer structure, which is a dielectric substrate B and a first metal layer A1 and a second metal layer A2 plated on both sides of the dielectric substrate. The metal material is copper, and the copper thickness is 17.5um; the material model of the dielectric substrate of the metamaterial unit is Rogers6002, with a thickness of 0.508mm, a dielectric constant of 2.94, and a loss tangent of 0.0012. The conjugate linear gradient slot antenna loaded with the metamaterial unit has the advantages of high gain, low sidelobe level, low return loss, low cost, easy processing, light weight, compact size, narrow beam width and relatively wide working frequency band.

[0073] Optionally, the first metal layer A1 includes two metal square rings (T1 and T2) with opposite opening directions, the second metal layer A2 is a long strip structure, and the metal square rings T1 and T2 form a "U"-shaped structure; the first metal layer A1 and the second metal layer A2 are both copper-plated.

[0074] The metal square rings T1 and T2 are located on the top layer, forming a "U"-shaped structure, with the width of the ring strips being 0.077mm, the side length of the metal square ring T1 being 0.78mm, the side length of the metal square ring T2 being 0.703mm, and the ring spacing between the metal square rings T1 and T2 being 0.077mm. The opening size at the center of the upper side of the metal square ring T1 is 0.16mm×0.077mm, and the opening size at the center of the lower side of the metal square ring T2 is 0.16mm×0.077mm; the dielectric substrate B is located in the middle layer, with a square opening and a side length of 1mm; the second metal layer A2 is located in the bottom layer, with a size of 1mm×0.16mm.

[0075] like Figure 6CAs shown, optionally, two rows of metallized through holes 42 are provided on the radiating arm of the conjugate linear tapered slot antenna 4, and periodic rectangular slots 43 are etched above the radiating arm.

[0076] Two rows of metallized through holes 42 are added on the radiating arm to extend the metallized through holes of SIW (substrate integrated waveguide) further toward the antenna radiating unit; and periodic rectangular slots 43 are arranged on the radiating arm to make the aperture field distribution more uniform.

[0077] There are 28 metamaterial unit structures on the left and right sides of the feed antenna 4. When the metamaterial units on the left are arranged periodically, the "U" shape faces upward, and when the metamaterial units on the right are arranged periodically, the "U" shape faces downward. The metamaterial units on both sides are arranged symmetrically about the center of the dielectric substrate; the conjugate linear gradient slot antenna loaded with metamaterial units on both sides has the advantages of high gain, low sidelobe level, light weight, low return loss, low cost, easy processing, light weight, compact size, narrow beam width and relatively wide working frequency band. After loading the SRR / Wire left-handed material, the E-plane sidelobe of the antenna is reduced by 5dB on the original basis to -17.1dB, and the 3dB beamwidth of the E-plane is reduced by 6° to 26.4°. The antenna gain is increased by 2dB to 15.7dB. There is no obvious change in the H-plane performance. The 3dB beamwidth of the H-plane is 24.2°, the antenna gain is 15.6dB, and the sidelobe is -15dB.

[0078] The test standing wave ratio of feed antenna 4 in the working frequency band of 33-37GHz is within the range of 1.2 to 1.5, and the specific size is 38.25mm×17mm×0.508mm. At the center frequency of 35GHz, the metasurface lens antenna is located in front of the feed antenna, and the spacing is one focal length, that is, 144mm. After the feed antenna is focused at the center of the focal plane, the E-plane 3dB beam width test result is 2.79°, and the H-plane 3dB beam width test result is 3.73°. The feed antenna gain is increased by 17dB after loading the metasurface lens antenna.

[0079] The structural improvement of the focusing lens antenna 3 and the feed antenna 4 effectively reduces the size and weight of the imaging system, reduces the manufacturing cost, increases the gain, reduces the sidelobe level, narrows the beam, and improves the resolution.

[0080] Combination Figure 1 and Figure 7As shown, the array of feed antennas 4 in the focal plane is arranged in a two-dimensional N×N manner. In this embodiment, the number of feed antennas 4 included in the antenna array is 9, and a two-dimensional 3×3 arrangement is adopted. The feed antennas 4 are arranged closely in turn horizontally, and the distance between adjacent antennas in the vertical direction of the feed antenna 4 is 15mm. In this embodiment, the field of view that can be covered by the array of feed antennas 4 is 8.37°×11.19°, and the resolution is 2.79°×3.73°. The array of feed antennas 4 in this embodiment is compactly arranged, covers a large field of view, has a small empty area, and has a large number of arrays. The radiation information of the target scene can be obtained faster during scanning.

[0081] like Figure 1 As shown, the radiometer receiver 5 is set corresponding to the feed antenna 4, and the radiometer receiver 5 is also arranged in a two-dimensional 3×3 manner. The radiometer receiver 5 is connected to the feed antenna 4 one by one; when scanning the target scene, the radiation information of the target scene can be obtained through multiple channels to improve the scanning speed and imaging speed.

[0082] Furthermore, the radiometer receiver 5 adopts a direct detection receiver, illustratively, with a size of 15 mm×15 mm×100 mm, and adopts a direct detection structure, without the need for a local oscillator and a mixer, thereby greatly reducing the size and cost.

[0083] The structure of the radiometer receiver 5 includes a digitally controlled attenuator with a gain control function; the main control module 8 sends an attenuation control signal to the control circuit of the radiometer receiver 5 through SPI communication to adjust the dynamic range of the radiometer receiver 5. Furthermore, the portable passive millimeter wave radiation detector system provided in this embodiment can be specially prepared as an 8 mm band passive focal plane imaging system.

[0084] The data acquisition and signal conditioning module 6 is provided with an acquisition port protection circuit to ensure that the output voltage range is within a safe acquisition range; the output voltage of the radiometer receiver 5 is acquired, and the voltage of multiple channels is pre-processed.

[0085] The image processing module 7 performs imaging and denoising on the pre-processed voltage data, and then performs image enhancement, and performs super-resolution reconstruction on the enhanced image to obtain a high-resolution image.

[0086] The display module 9 displays the high-resolution microwave image after the final processing.

[0087] The data storage module 10 stores the processed high-resolution microwave image data.

[0088] The power module 11 is powered by a lithium battery pack and is connected to each module through a power conversion circuit to provide each module with the required voltage so that each module maintains a normal working state.

[0089] Optionally, the metal housing is further provided with a button and an angle sensor (not shown), and both the button and the angle sensor are connected to the main control module;

[0090] An angle sensor is used to record the corresponding relationship between the output voltage of the radiometer receiver and the detector posture, and transmit it to the image processing module through the main control module. The image processing module uses the posture angle information obtained by the angle sensor during the handheld scanning imaging process to correct the pre-processed voltage data and then perform image processing;

[0091] The main control module 8 uses a microprocessor, and the main control module is used to control each module according to the operation of the keys.

[0092] By clicking different buttons on the metal shell, the main control module 8 adjusts each module in the portable passive millimeter wave radiation detector system. For example, the gain of the radiometer receiver 5 can be adjusted by buttons. In this embodiment, the main control module 8 can be FPGA, ARM, etc.

[0093] The main control module 8 adopts a microprocessor to reduce the size of the instrument; the receiver has a gear adjustment function and can detect a wide range of radiation brightness temperatures.

[0094] The technical solution of the embodiment of the present invention improves the structure of the focusing lens antenna and the feed antenna. The focusing lens antenna adopts a metasurface lens antenna, and the feed antenna adopts a conjugate linear gradient slot antenna loaded with metamaterial units on both sides, which reduces the size of the antenna and reduces the weight. At the same time, the feed antenna adopts a two-dimensional N×N arrangement method, which increases the number of antenna receiver channels, speeds up the scanning speed, improves the image quality, and increases the diversity of array arrangement; the main control module adopts a microprocessor, which can process the collected data in real time, and is small in size and low in cost. The image is corrected by an angle sensor, which improves the image quality and the feasibility of handheld scanning, and enhances the portability of the instrument. The portable multi-channel passive millimeter wave radiation detector system achieves small size, low cost, fast imaging speed, high imaging resolution, and has the beneficial effect of portable use.

[0095] On the basis of the above embodiment, further, a method for using a portable passive millimeter wave radiation detector system includes:

[0096] S1: Start the portable passive millimeter wave radiation detector, and adjust the radiometer receiver position by pressing buttons according to the target scene to select the appropriate dynamic range;

[0097] S2: Calibrate the radiometer receiver of the multi-channel antenna array;

[0098] S3: Perform inconsistency correction on the radiometer receiver of the multi-channel antenna array;

[0099] S4: A handheld portable passive millimeter wave radiation detector scans the target scene, collects voltage data corresponding to the radiation information of the target scene and performs preprocessing;

[0100] S5: The image processing module uses the posture angle information obtained by the angle sensor during the handheld scanning imaging process to correct the pre-processed voltage data, and then performs image denoising, image enhancement and super-resolution reconstruction operations;

[0101] S6: The screen of the portable passive millimeter wave radiation detector displays the final high-resolution image of the scene and stores the data.

[0102] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A portable multi-channel passive millimeter wave radiation detector system, characterized in that: include: Metal housing; A focusing lens antenna fixedly arranged at one end of the metal shell, wherein the focusing lens antenna adopts a super-surface lens antenna; A feed antenna arranged opposite to the focusing lens antenna is arranged inside the metal shell, the feed antenna is connected to the radiometer receiver, and the feed antenna adopts a conjugate linear gradient slot antenna with metamaterial units loaded on both sides, and is arranged in a two-dimensional N×N manner on the focal plane, N≥2; The electromagnetic waves radiated by the target scene to be measured are gathered by the focusing lens antenna to be received by the feed antenna and transmitted to the radiometer receiver; The voltage data output by the radiometer receiver is processed by the processing module to generate a target scene image and display it; Among them, the metasurface lens antenna is composed of three different metasurface units, and the metal layer structures of the three metasurface units are different; the aperture field of the metasurface unit is square, and the three metasurface units all include M+1 metal layers and M dielectric substrates arranged at intervals, and a metal inner circle is arranged at the center of each metal layer; the aperture field of the first metasurface unit is square, and the metal layer includes a square ring a1, a circular ring a2 and an inner circle R, and the radius of the metal inner circle R is smaller than the radius of the circular ring a2; the aperture field of the second metasurface unit is square, and the metal layer includes a square ring a1 and an inner circle R; the aperture field of the third metasurface unit is square, and the metal layer is the first part c generated by the hollowed-out embedded circle on the square metal plate; The phase of the metasurface lens antenna is designed with n bit discretization, which divides the 360° phase into 2 n discrete phase values, according to the formula The phase value required for each position is calculated; where the lens center position coordinates are (0,0), (x, y) are the unit position coordinates in the metasurface lens, λ0 is the wavelength in free space, and f is the focal length of the metasurface lens. is the reference phase of the central unit of the metasurface lens; The metasurface unit with the highest transmittance among the three metasurface units corresponding to each discrete phase value is selected as the target metasurface unit corresponding to this discrete phase value; the phase value calculated according to each target position is compared with 2 n The target metasurface unit corresponding to the closest discrete phase value is selected and set at the target position to form a metasurface lens antenna.

2. The system according to claim 1, characterized in that The phase and amplitude of the transmitted electromagnetic wave are regulated by changing the metal inner circle radius of the metal layer of the metasurface unit.

3. The system according to claim 1, characterized in that The metamaterial unit comprises a three-layer structure, which is a dielectric substrate, a first metal layer and a second metal layer plated on both sides of the dielectric substrate.

4. The system according to claim 3, characterized in that The first metal layer comprises two metal square rings with opening directions opposite to each other, the second metal layer is a long strip structure, and the two metal square rings form a "U"-shaped structure; the first metal layer and the second metal layer are both copper-plated.

5. The system according to claim 3, characterized in that Two rows of metallized through holes are arranged on the radiation arm of the conjugate linear gradient slot antenna, and a periodic rectangular slot is etched above the radiation arm.

6. The system according to claim 1, characterized in that The feed antennas are arranged closely in sequence laterally.

7. The system according to claim 6, characterized in that The radiometer receiver is arranged corresponding to the feed antenna, and the radiometer receiver is connected to the feed antenna in a one-to-one correspondence; The radiometer receiver adopts a direct detection receiver.

8. The system according to claim 1, characterized in that The processing module includes: a data acquisition and signal conditioning module connected to the radiometer receiver, the data acquisition and signal conditioning module is connected to the image processing module and the main control module, and the main control module is also connected to the image processing module, the display module and the data storage module; the data acquisition and signal conditioning module and the image processing module are used to process the voltage data output by the radiometer receiver and generate target scene image data; the display module is used to display the target scene image, and the main control module is used to control each module; A power module is also provided inside the metal shell to connect the modules and supply power to the modules; The metal shell is also provided with a handheld handle, buttons and an angle sensor, and the buttons and the angle sensor are connected to the main control module; The angle sensor is used to record the corresponding relationship between the output voltage of the radiometer receiver and the detector posture, and transmit it to the image processing module through the main control module to correct the obtained data; The main control module adopts a microprocessor, and the main control module is used to control each module according to the operation of the key.

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