An array antenna with radiation characteristics in a stable array

Abstract

The present application discloses an array antenna with radiation characteristics in a stable array, including: a transmitting array and a receiving array; the transmitting array includes waveguide ports arranged in a one-dimensional linear array for converting a guided wave into a space wave; the receiving array includes waveguide ports arranged in a one-dimensional linear array for converting a space wave into a guided wave; on both sides of the waveguide ports arranged in the one-dimensional linear array, metal ridges are configured in the same direction as the arrangement direction of the waveguide ports. The purpose of the present application is to optimize the radiation characteristics of the waveguide array antenna and improve the azimuth resolution of the system.

Description

Technical Field

[0001] This application relates to the field of antenna technology, and particularly to an array antenna with stable in-array radiation characteristics for a human body security inspection imaging system. Background Art

[0002] An array antenna is an antenna system composed of many identical antennas arranged according to a certain rule. Compared with a single antenna, an array antenna provides better performance, more functions, and greater design freedom. More and more communication, detection, and imaging systems rely on complex array antennas rather than independent antennas to work.

[0003] A human body security inspection imaging system usually operates in the millimeter wave or terahertz frequency band. Currently, the mainstream human body security inspection imaging systems adopt active imaging, which has complete signal transmission and reception channels, can provide higher signal-to-noise ratio and target contrast, and is essentially a millimeter wave coherent imaging radar, with imaging quality and accuracy significantly higher than passive imaging.

[0004] The particularity of the application scenarios of active imaging human body security inspection technology requires it to have as high detection accuracy as possible. In an active imaging human body security inspection system, parameters such as the bandwidth, radiation pattern, polarization characteristics, and gain of the antenna system will all have an important impact on the imaging effect of the system. There are two technical paths for existing active imaging human body security inspection systems. One uses purely electrically controlled scanning. The antenna array is a planar array sparsely arranged according to a certain rule, and realizes planar electrical scanning millimeter wave imaging based on digital beamforming technology. Due to the high cost of this type of system, only a few manufacturers currently adopt this technical route. The other uses a combination of electrical scanning and mechanical scanning. The transmitting and receiving antenna pairs are arranged in a one-dimensional linear array manner. The antenna pairs on the linear array are sequentially turned on by a switch control line for signal transmission and reception to achieve one-dimensional electrical scanning. At the same time, a mechanical structure drives the antenna arm to achieve two-dimensional mechanical scanning, and holographic imaging of the target is realized through synthetic aperture signal processing. This technical route is the mainstream technical route widely adopted at home and abroad.

[0005] Since the antenna element spacing of an electrically scanned linear array is usually very small, the transmitting and receiving antennas are arranged closely and highly integrated with the backend circuit. An increase in the lobe width will significantly increase the coupling of the antenna elements to the floor and adjacent elements, which will instead affect the in-array radiation characteristics of the antenna elements, resulting in dispersion and distortion of the radiation pattern, thereby deteriorating the azimuth resolution of the system. Summary of the Invention

[0006] The embodiments of this application provide an array antenna with stable in-array radiation characteristics, aiming to optimize the radiation characteristics of the waveguide array antenna, improve the azimuth resolution of the system, and is particularly applicable to the array antenna for human body security inspection imaging.

[0007] This application proposes a radiation characteristic array antenna in a stable array, including a transmitting array and a receiving array. The transmitting array includes waveguide ports arranged in a one-dimensional linear array for converting the guided wave into a space wave; the receiving array includes waveguide ports arranged in a one-dimensional linear array for converting the space wave into a guided wave; on both sides of the waveguide ports arranged in the one-dimensional linear array, metal ridges are configured in the same direction as the arrangement direction of the waveguide ports.

[0008] Preferably, around the waveguide port, a choke groove is configured. The mouth surface of the choke groove is flush with the mouth surface of the waveguide port, and the grooving direction of the choke groove is parallel to each side of the waveguide port.

[0009] Preferably, the configured size of the metal ridge is: the width of the metal ridge is 0.2λc to λc, and the distance from the center of the metal ridge to the center of the waveguide port is λc to 4λc.

[0010] Preferably, the size of the choke groove is: the depth is 0.05λc to 0.5λc, and the width is 0.1λc to 0.5λc.

[0011] The transmitting array is composed of multiple transmitting modules, and each transmitting module includes a printed circuit board and a metal shell; the receiving array is composed of multiple receiving modules, and each receiving module includes a printed circuit board and a metal shell; the metal shell covers the printed circuit board, and the surface of the metal shell forms the waveguide port. Generally, each transmitting module or receiving module includes multiple waveguide ports arranged in a one-dimensional linear array.

[0012] Furthermore, an absorbing material is used for covering. For example, the surface of the metal shell on the side of the metal ridge away from the waveguide port is covered with the absorbing material, and / or the absorbing material is filled in the gap between the metal ridge and the waveguide port, and / or the absorbing material is filled in the choke groove.

[0013] The above at least one technical solution adopted in the embodiments of this application can achieve the following beneficial effects:

[0014] Improve the isolation between the transmitting and receiving antennas, reduce the deviation of the maximum radiation direction of the radiation pattern; suppress the floor effect and improve the distortion of the radiation pattern. Loading the choke groove can further reduce the sidelobe level and improve the system resolution. Description of the Drawings

[0015] The drawings described herein are used to provide a further understanding of this application and constitute a part of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0016] Figure 1 It is a structural diagram of the antenna transmitting module and receiving module;

[0017] Figure 2It is the structure diagram of the metal housing of the transmitting module and the receiving module;

[0018] Figure 3 It is the comparison of the isolation of the loaded and unloaded metal-ridge transceiver antennas;

[0019] Figure 4 It is the comparison of the maximum radiation directions of the loaded and unloaded metal-ridge antennas;

[0020] Figure 5 It is the surface current distribution of the aperture of the unloaded choke slot antenna;

[0021] Figure 6 It is the surface current distribution of the aperture of the loaded choke slot antenna;

[0022] Figure 7 It is the E-plane and H-plane lobe widths of the loaded and unloaded choke slots;

[0023] Figure 8 It is the H-plane sidelobe level of the loaded and unloaded choke slots.

[0024] Among them, 01 is the transmitting module; 102 is the receiving module; 103 is the oscillator of the transmitting antenna unit; 104 is the second-stage switch of the transmitting module; 105 is the first-stage switch of the transmitting module; 106 is the millimeter-wave signal input port; 107 is the oscillator of the receiving antenna unit; 108 is the second-stage switch of the receiving module; 109 is the low-noise amplifier; 110 is the first-stage switch of the receiving module; 111 is the millimeter-wave signal output port; 201 is the metal housing of the antenna; 202 is the printed circuit board of the antenna; 203 is the upper metal ridge; 204 is the lower metal ridge; 205 is the antenna radiation waveguide (horn) aperture; 206 is the choke slot below the waveguide (horn) aperture; 207 is the choke slot above the waveguide (horn) aperture; 208 is the choke slot on the side of the waveguide (horn) aperture; 209 is the absorbing material. Specific embodiments

[0025] To make the purpose, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0026] The following will describe in detail the technical solutions provided by each embodiment of the present application in conjunction with the drawings.

[0027] Figure 1 It is the structure diagram of the antenna transmitting module and the receiving module.

[0028] This application discloses an array antenna structure with a stable in-array radiation pattern, which takes into account both wide-beam characteristics and radiation pattern stability and is applicable to synthetic aperture imaging human body security inspection systems or other imaging and detection systems. Among them:

[0029] The antenna array is a two-column linear array, divided into a transmitting array and a receiving array. The transmitting array is composed of multiple transmitting modules, and each transmitting module includes a printed circuit board and a metal housing. The printed circuit board includes a switch for controlling the open / closed state of the channel, a signal transmission line, an antenna element, and a control circuit part. The metal housing covers the printed circuit board and is fixed by means such as screws or eutectic sintering. In addition to playing a protective role, it also has a waveguide port (or horn mouth) for converting the guided wave into a space wave and a structure for improving the radiation characteristics, etc.

[0030] The receiving array is composed of multiple receiving modules. The receiving array is composed of multiple receiving modules, and each receiving module includes a printed circuit board and a metal housing. The printed circuit board includes a switch for controlling the open / closed state of the channel, a low-noise amplifier, a signal transmission line, an antenna element, and a control circuit part. The metal housing covers the printed circuit board and is fixed by means such as screws or eutectic sintering. In addition to playing a protective role, it also has a waveguide port (or horn mouth) for converting the space wave into a guided wave and a structure for improving the radiation characteristics, etc.

[0031] Since the radiation aperture surface of the waveguide port forms a protrusion on the metal housing, the height of the protrusion is, for example, 7.5 mm relative to the bottom plate of the metal housing.

[0032] The maximum radiation direction of the antenna module described in this patent is perpendicular to the printed circuit board, and the antenna radiation form is broadside. Also, in the human body security inspection imaging array, the transmitting and receiving antennas should be as close as possible to reduce the single-station imaging error. The transmitting and receiving array units can adopt working modes such as one transmit and one receive, one transmit and two receive, or one transmit and multiple receive. In any mode, the in-array units will be affected by the adjacent transmit (receive) units, resulting in pattern distortion.

[0033] The present invention proposes that on both sides of the waveguide ports arranged in the one-dimensional linear array, metal ridges are arranged in the same direction as the arrangement direction of the waveguide ports. For example, rectangular metal ridges are loaded on both sides of the unit radiation ports of the metal housings of the transmitting and receiving antenna modules. The height of the metal ridges is the same as or close to the height of the antenna waveguide port (horn mouth). The width of the metal ridges is 0.2λc to λc, and the center distance of the metal ridges from the center of the antenna horn mouth is λc to 4λc. To improve the isolation between the transmitting and receiving antennas and reduce the deviation of the maximum radiation direction of the pattern caused by the bottom plate asymmetry.

[0034] To further optimize the radiation characteristics, this patent proposes to add choke grooves at the antenna aperture. Since the radiation aperture of the waveguide opening forms a raised platform on the metal housing, around the waveguide opening, choke grooves are configured on the raised platform, so that metal walls surrounding the waveguide opening are formed on both sides of the choke grooves. The aperture surface of the choke groove is flush with the aperture surface of the waveguide, and the grooving direction of the choke groove is parallel to each side of the waveguide opening. The choke groove can limit the surface current of the excited unit to the vicinity of the antenna aperture and the choke groove, avoiding the influence of adjacent units. The position of the choke groove should be as close as possible to the edge of the antenna aperture on the basis of mechanical structure strength and engineering feasibility to achieve a better choking effect, with a depth of 0.05λc to 0.5λc and a width of 0.1λc to 0.5λc.

[0035] In the above-mentioned human body security inspection system using synthetic aperture imaging, the azimuth system resolution is determined by the following formula

[0036]

[0037] where λc is the wavelength corresponding to the system center frequency, and θ is the 3dB lobe width (HPBW) of the antenna element in the array. It can be seen that the wider the lobe width of the antenna element, the higher the system resolution.

[0038] Figure 2 It is a structural diagram of the metal housing of the transmitting module and the receiving module.

[0039] Furthermore, an absorbing material is used for covering. For example, an absorbing material is covered on the surface of the metal housing on the side of the metal ridge away from the waveguide opening, and / or an absorbing material is filled in the gap between the metal ridge and the waveguide opening, and / or an absorbing material is filled in the choke groove. 209 is an optional absorbing material. The absorbing material can further absorb the surface current of the housing, suppress the floor effect, and improve the pattern distortion. However, the introduction of the absorbing material has the side effect of reducing the antenna efficiency. Therefore, it should be decided whether to install it according to the actual situation.

[0040] For example, when the operating frequency is 32GHz - 39GHz. After the millimeter-wave signal is input to the port 106, it passes through the first-stage single-pole four-throw switch 105 and the second-stage single-pole four-throw switch 106, and is radiated into space by the transmitting antenna element oscillator 103. After being reflected by the target, the echo signal is received by the receiving antenna element oscillator 107, passes through the second-stage single-pole four-throw switch 108, the low-noise amplifier 109 and the first-stage single-pole four-throw switch 110, and is output from the millimeter-wave output port 111 to the signal processing system for analysis and imaging.

[0041] According to the reciprocity theorem of antennas, passive antennas are reversible, that is, the same antenna can be used as both a transmitting antenna and a receiving antenna. The basic characteristic parameters of the same antenna as a transmitter or receiver are the same. For design convenience, the transmitting and receiving antenna elements are usually designed in the same form. In this implementation, the antenna element uses a back-cavity reflector horn antenna fed by a microstrip monopole, and the antenna polarization form is vertical linear polarization. It should be noted that the antenna radiation element can adopt other antenna forms, including but not limited to slot antennas, horn antennas, dielectric column antennas, double-ridge antennas, etc., or adopt other polarization methods, such as horizontal linear polarization, circular polarization, etc. In this specific implementation, the improvement and optimization of the antenna radiation characteristics are mainly achieved on the metal shell of the antenna module. Specifically, two rows of metal ridges 203 and 204 are loaded on the upper and lower sides of the antenna radiation port 205. The height of the loaded metal ridge is 7.5 mm, the width is 2 mm, and the distance from the center of the antenna horn mouth is 8 mm. This structure can improve the isolation between the transmitting and receiving antennas and suppress the deviation of the maximum radiation direction of the antenna E-plane pattern caused by the asymmetry of the physical structure of the antenna module.

[0042] Figure 3 Comparison of the isolation between the transmitting and receiving antennas with and without the loaded metal ridge. It can be seen that introducing the metal ridge can increase the isolation between the transmitting and receiving antennas by about 6 dB.

[0043] Figure 4 Comparison of the maximum radiation direction of the antenna with and without the loaded metal ridge. It can be seen that introducing the metal ridge significantly improves the main lobe deviation problem at the high-frequency end.

[0044] Different from isolated antennas, antennas located in an array will be affected by the coupling of adjacent elements. In this implementation case, under the control of the first and second stage switches, only one pair of transmitting and receiving antennas is in the open state at the same time. However, the antennas in the off state still have a non-negligible impact on the open antennas. Taking the transmitting antenna in this implementation case as an example, the near-field energy near the aperture of the open antenna will be coupled to the nearby antennas, exciting surface currents, which makes the equivalent aperture of the antenna larger, the HPBW narrower, and the sidelobe level increase. And the narrower HPBW will reduce the resolution of the system, and the receiving antenna is the same. In this implementation case, in order to alleviate or eliminate this impact, choke grooves 206, 207, and 208 are loaded near the antenna aperture. The width of the loaded choke groove is 0.5 mm, and the depth is 2 mm. This choke groove can limit the surface current of the antenna aperture near the aperture and reduce the equivalent antenna aperture.

[0045] Figure 5 Surface current distribution on the antenna aperture without the loaded choke groove Figure 6For loading the surface current distribution of the choke groove antenna aperture. It can be seen that the choke groove effectively confines the surface current excited by the antenna radiation to the vicinity of the antenna aperture and the choke groove.

[0046] Figure 7 For the E-plane and H-plane lobe widths of the loaded and unloaded choke grooves. It can be seen that loading the choke groove can broaden the lobe width, thereby improving the system resolution.

[0047] Figure 8 For the H-plane sidelobe levels of the loaded and unloaded choke grooves. It can be seen from the figure that loading the choke groove can reduce the sidelobe level at the low-frequency end.

[0048] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, commodity or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "including a..." does not exclude the presence of additional identical elements in the process, method, commodity or device comprising the said element.

[0049] The above are only embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A radiation characteristic array antenna in a stable array, characterized in that, Including: A transmitting array and a receiving array; The transmitting array includes waveguide ports arranged in a one-dimensional linear array for converting a guided wave into a space wave; the receiving array includes waveguide ports arranged in a one-dimensional linear array for converting a space wave into a guided wave; on both sides of the waveguide ports arranged in the one-dimensional linear array, metal ridges are configured in the same direction as the arrangement direction of the waveguide ports; in the gap between the metal ridges and the waveguide ports, an absorbing material is filled.

2. The array antenna with radiation characteristics in the stable array according to claim 1, wherein A choke groove is configured around the waveguide port; The mouth surface of the choke groove is flush with the mouth surface of the waveguide port, and the grooving direction of the choke groove is parallel to each side of the waveguide port.

3. The array antenna with radiation characteristics in the stable array according to claim 1, wherein For the configured size of the metal ridge, the width of the metal ridge is 0.2λc to λc, and the distance from the center of the metal ridge to the center of the waveguide port is λc to 4λc.

4. The array antenna with radiation characteristics in the stable array according to claim 2, wherein For the size of the choke groove, the depth is 0.05λc to 0.5λc, and the width is 0.1λc to 0.5λc.

5. The array antenna with radiation characteristics in the stable array according to claim 1, wherein The transmitting array is composed of multiple transmitting modules, and each transmitting module includes a printed circuit board and a metal housing; the receiving array is composed of multiple receiving modules, and each receiving module includes a printed circuit board and a metal housing; The metal housing covers the printed circuit board, and the surface of the metal housing forms the waveguide port.

6. The array antenna with radiation characteristics in the stable array according to claim 1, wherein An absorbing material is covered on the surface of the metal housing on the side of the metal ridge away from the waveguide port.

7. The array antenna with radiation characteristics in the stable array according to claim 2, wherein An absorbing material is filled in the choke groove.

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