A millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna

Abstract

The present invention belongs to the field of millimeter wave radar detection, and relates to the antenna structure in a millimeter wave micro detection system. Specifically, a millimeter wave center-fed forward-tilted fan-shaped beam microstrip array antenna is provided to solve the problems of the existing forward-tilted beam antenna, such as the inability to obtain the maximum radiation efficiency, large matching loss, and low far-field radiation efficiency. The present invention adopts the middle feeding method to realize the function of the pitch angle beam forward tilt of the antenna far-field radiation pattern. Specifically, the center-fed line array structure is realized by parallel feeding the radiation sub-arrays on the left and right sides, so as to realize the pitch angle beam forward tilt by superimposing the radiation phase at the far-field specified radiation angle; at the same time, the present invention can flexibly utilize the reserved space of the millimeter wave small radar front-end module by increasing or decreasing the number of array elements on both sides of the feeding position, avoiding assembly position restrictions, and obtaining higher antenna radiation efficiency, thereby meeting the demand of electronic technology development for high-performance radar detectors.

Description

Technical Field

[0001] The present invention belongs to the field of millimeter wave radar detection, relates to an antenna structure in a millimeter wave micro detection system, and specifically provides a millimeter wave central-fed forward-tilted fan-beam microstrip array antenna. Background Art

[0002] With the continuous development of electronic systems, the requirements for miniaturization of electronic equipment are becoming more and more stringent. In the field of millimeter-wave radar detection, the size limitation of the front-end module of the millimeter-wave small radar makes it impossible to adjust the feeding position and assembly of the antenna at will. Specifically, the millimeter-wave micro-detector has the technical requirement of realizing early detection of the target, which makes the antenna far-field radiation pitch beam have certain inclination requirements. At present, the traditional way to achieve antenna beam forward tilt usually adopts the end-fed array type. However, when the interconnection position between the front-end transceiver branch of the system and the antenna is fixed and cannot be adjusted, the end-fed antenna cannot obtain the maximum radiation efficiency due to the limitation of the assembly position, and the excessively long feed line will also produce a large matching loss, thereby affecting the far-field radiation efficiency of the antenna. Summary of the invention

[0003] The purpose of the present invention is to propose a millimeter-wave center-fed forward-tilted fan-shaped beam microstrip array antenna to solve the problems of the existing forward-tilted beam antenna that cannot obtain the maximum radiation efficiency, large matching loss, and low far-field radiation efficiency. The present invention adopts the middle feeding method to realize the function of the pitch angle beam forward tilt of the far-field radiation pattern of the entire array antenna. At the same time, it can flexibly utilize the reserved space of the millimeter-wave small radar front-end module by increasing or decreasing the number of array elements on both sides of the feeding position, avoid assembly position restrictions, and obtain higher antenna radiation efficiency, thereby meeting the needs of electronic technology development for high-performance radar detectors.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A millimeter-wave center-fed forward-tilted fan-shaped beam microstrip array antenna comprises: a dielectric substrate, a radiating array, a metal floor and a feeding structure; wherein the metal floor is arranged on the lower surface of the dielectric substrate, and the radiating array is arranged on the upper surface of the dielectric substrate; the radiating array comprises: a left radiating subarray and a right radiating subarray, the left radiating subarray and the right radiating subarray respectively adopt an end-fed line array structure, and the left radiating subarray and the right radiating subarray are fed in parallel by the feeding structure, so that the radiating array forms a center-fed line array structure.

[0006] Furthermore, the right radiation subarray is composed of a plurality of right microstrip array elements, and adjacent right microstrip array elements are sequentially connected by feeder lines, and the length of the feeder lines is D R , and D R >λ g / 2,λ g is the medium wavelength.

[0007] Furthermore, in the right radiation subarray, passive loading structures are respectively arranged between adjacent right microstrip array elements, the passive loading structures are composed of two passive microstrip patches, the passive loading structure is arranged in the middle position between adjacent right microstrip array elements, and the two passive microstrip patches are symmetrically arranged on both sides of the feed line.

[0008] Furthermore, the left radiation subarray is composed of a plurality of left microstrip array elements, and adjacent left microstrip array elements are sequentially connected by feeder lines, and the length of the feeder lines is D L , and D L <λ g / 2,λ g is the medium wavelength.

[0009] Furthermore, in the left radiating subarray, decoupling structures are respectively arranged between adjacent left microstrip array elements, the decoupling structures are composed of two grounded microstrip patches, the decoupling structure is arranged in the middle position between adjacent left microstrip array elements, and the two grounded microstrip patches are symmetrically arranged on both sides of the feed line.

[0010] Furthermore, the phases of the right radiation sub-array and the left radiation sub-array are superimposed in the direction of the preset forward tilt angle to obtain the forward tilt far-field radiation elevation beam pointing.

[0011] Based on the above technical solution, the beneficial effects of the present invention are:

[0012] The present invention provides a millimeter-wave center-fed forward-tilted fan-shaped beam microstrip array antenna. Compared with the end-fed structure in the traditional forward-tilted beam antenna (waveguide slot array or microstrip linear array), the present invention adopts the middle feeding method to realize the function of the pitch angle beam forward tilt of the far-field radiation pattern of the entire array antenna. Specifically, the center-fed linear array structure is realized by parallel feeding of the left and right radiating sub-arrays, so that the radiation phase is superimposed at the far-field specified radiation angle to realize the pitch angle beam forward tilt; at the same time, the passive loading structure and the decoupling structure between the microstrip array elements are used to overcome the influence of the grating lobe and the mutual coupling, so as to improve the radiation efficiency of the antenna; and each radiating sub-array adopts the directional pattern to comprehensively suppress the sidelobe level, so that the total far-field radiation after superposition obtains a lower sidelobe level; finally, under the conditions of limited assembly space and specified feeding position, the present invention adopts 16 antenna array elements to realize the performance indicators of 19° beam forward tilt and sidelobe level lower than -10dB at the operating frequency of Ka band, and the antenna has a good impedance matching bandwidth.

[0013] In summary, the present invention provides a millimeter-wave central-fed forward-tilted fan-beam microstrip array antenna, which overcomes the assembly limitations of millimeter-wave small radar front-end modules, realizes the far-field radiation pitch beam forward tilt function, and has stable performance, high structural reliability, and is easy to conform to the carrier surface, and can meet the application requirements of high-performance radar detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna in the present invention.

[0015] Figure 2 It is a structural schematic diagram of the passive loading structure of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna in the present invention.

[0016] Figure 3 It is a structural schematic diagram of the passive loading structure of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna in the present invention.

[0017] Figure 4 It is the far-field radiation pattern of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna at 36.1 GHz in the present invention.

[0018] Figure 5 It is the far-field radiation pattern of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna at 36.3 GHz in the present invention.

[0019] Figure 6 It is the far-field radiation pattern of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna at 36.5 GHz in the present invention.

[0020] Figure 7 This is a graph showing the impedance bandwidth results of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna in the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0022] This embodiment provides a millimeter wave center-fed forward tilted fan-beam microstrip array antenna, the structure of which is as follows: Figure 1 As shown, it specifically includes: a dielectric substrate, a radiating array, a metal floor and a feeding structure, wherein the metal floor is arranged on the lower surface of the dielectric substrate, and the radiating array is arranged on the upper surface of the dielectric substrate; the radiating array includes: a left radiating sub-array and a right radiating sub-array, the left radiating sub-array and the right radiating sub-array respectively adopt an end-fed line array structure, and the left radiating sub-array and the right radiating sub-array are fed in parallel by the feeding structure, so that the radiating array forms a middle-fed line array structure.

[0023] Furthermore, the right radiation subarray adopts an end-fed array composed of 8 microstrip array elements, which are the first right microstrip array element to the eighth right microstrip array element in sequence from the feeding position to the right, and the 8 right microstrip array elements are connected in sequence through feeders, and the feeder lengths between adjacent right microstrip array elements are D R , and D R >λ g / 2,λ g is the wavelength of the medium; that is, adjust the feed line length D between the right microstrip array elements R , which is also the array element spacing, making it greater than half the medium wavelength λ g , the phases of adjacent microstrip array elements lag behind each other by a certain phase in turn, so that the far-field radiation elevation beam pointing of the right radiating sub-array deviates from the antenna normal and deviates toward the load end.

[0024] Furthermore, the left radiation subarray also uses an end-fed array composed of 8 microstrip array elements, which are the first left microstrip array element to the eighth left microstrip array element from the feeding position to the right, and the 8 left microstrip array elements are connected in sequence through feeders, and the feeder lengths between adjacent left microstrip array elements are D L , and D L <λ g / 2,λ g is the medium wavelength; that is, adjust the feed line length D between the left microstrip array elements L , which is also the array element spacing, making it less than half the medium wavelength λ g , the phases of adjacent microstrip array elements advance by a certain phase in turn, so that the far-field radiation elevation beam pointing of the left radiating sub-array deviates from the antenna normal and tilts forward toward the feed end.

[0025] On this basis, adjust the feeder length LF of the right radiating subarray R (i.e., the feeder length between the first right microstrip array element and the feeding position) and the feeder length LF of the left radiating subarray L (that is, the feed line length between the first left microstrip array element and the feeding position), so that the phases of the right radiating sub-array and the left radiating sub-array are superimposed in the direction of the required forward tilt angle, thereby obtaining a beam forward tilt far-field radiation pattern.

[0026] Furthermore, for the right radiating subarray, since its forward-tilted beam is biased toward the load end, the spacing between the right microstrip array elements is greater than half the wavelength of the medium, resulting in grating lobes in the visible area of ​​the beam. In order to suppress the influence of the grating lobes, a passive loading structure is set between adjacent microstrip array elements of the right radiating subarray, and the weak coupling field between the passive loading structures is used to equivalently reduce the spacing between the right microstrip array elements, thereby weakening the influence of the grating lobes; at the same time, for the left radiating subarray, since its forward-tilted beam is biased toward the feeding end, the spacing between the left microstrip array elements is less than half the wavelength of the medium, and the mutual coupling between the array elements increases, affecting the precise beam pointing of the far-field radiation pattern. Therefore, a decoupling structure is set between adjacent microstrip array elements of the left radiating subarray, thereby reducing the mutual coupling between the left microstrip array elements. The decoupling structure is as follows: Figure 2 As shown in FIG. 1 , it is composed of two grounded microstrip patches. The decoupling structure is set in the middle position between the adjacent left microstrip array elements. The two grounded microstrip patches are symmetrically set on both sides of the feed line. The passive loading structure is shown in FIG. Figure 3As shown, it is composed of two passive microstrip patches, the passive loading structure is arranged in the middle position between adjacent right microstrip array elements, and the two passive microstrip patches are symmetrically arranged on both sides of the feed line.

[0027] It should also be noted that in the left and right radiating sub-arrays, the excitation amplitude of the microstrip array elements can be adjusted by the width parameters W1~W8 and W9~W 16 Adjust the radiation power ratio of each microstrip patch to change the array factor and radiation pattern of the microstrip array antenna; and adjust the amplitude distribution of the microstrip array element aperture to approximately meet the comprehensive distribution of the Chebyshev antenna, so that the microstrip array antenna obtains a more ideal sidelobe level; in addition, accurate beam pointing is to approximate each microstrip array element as a point element or a plane element to calculate the far-field phase superposition, and the microstrip array antenna is a plane antenna, and the length of the radiation side has an impact on the feeding phase of the antenna. Therefore, by adjusting the microstrip array element length parameters L1~L8 and L9~L 16 Fine-tune the phase distribution of the left and right radiating sub-arrays to correct the effect of the antenna feed line length on the microstrip array element phase, thereby obtaining ideal far-field beam pointing;

[0028] Specifically, the performance parameters of the microstrip array antenna in this embodiment are: 1) the center frequency is 35 GHz, the impedance bandwidth is 3 GHz; 2) the gain is 16 dBi, and the sidelobe suppression level is -10.2 dB; 3) the elevation angle pointing deviates from the normal by 19°, and the half-power beam width is 5°; 4) the half-power beam width in the horizontal direction is greater than 80°; the substrate of the microstrip array antenna is Rogers4003C, and the specific size parameters are shown in Table 1, where ε r represents the dielectric constant of the substrate, ε e represents the equivalent relative dielectric constant, h represents the substrate thickness, t represents the metal thickness of the patch and microstrip surface, and f g represents the center frequency of the microstrip array antenna, λ g represents the dielectric wavelength of the microstrip array antenna, a1 and b1 represent the length and width of the patch in the passive loading structure, a2 and b2 represent the length and width of the patch in the decoupling structure, g represents the feed width, W1 to W8 represent the width of the first right microstrip array element to the eighth right microstrip array element in the right radiation subarray, L1 to L8 represent the length of the first right microstrip array element to the eighth right microstrip array element in the right radiation subarray, W9 to W 16 The widths of the first left microstrip array element to the eighth left microstrip array element in the left radiation subarray are L9 to L 16 represents the length from the first left microstrip array element to the eighth left microstrip array element in the left radiation subarray, D L Indicates the length of the feeder between the left array elements, LF L Indicates the length of the left branch feeder, D RIndicates the length of the feeder line between the right array elements, LF R Indicates the length of the right branch feeder.

[0029] Table 1

[0030] parameter value parameter value <![CDATA[ε r ]]> 3.55 <![CDATA[W1, W9]]> <![CDATA[0.26λ g ]]> <![CDATA[ε e ]]> 2.8 <![CDATA[W2, W 10 ]]> <![CDATA[0.38λ g ]]> h 8 mil <![CDATA[W3, W 11 ]]> <![CDATA[0.49λ g ]]> t 15um <![CDATA[W4, W 12 ]]> <![CDATA[0.55λ g ]]> <![CDATA[f g ]]> 36.3 GHz <![CDATA[W5, W 13 ]]> <![CDATA[0.55λ g ]]> <![CDATA[λ g ]]> 5.12 mm <![CDATA[W6, W 14 ]]> <![CDATA[0.49λ g ]]> <![CDATA[a1]]> <![CDATA[0.16λ g ]]> <![CDATA[W7, W 15 ]]> <![CDATA[0.38λ g ]]> <![CDATA[b1]]> <![CDATA[0.19λ g ]]> <![CDATA[W8, W 16 ]]> <![CDATA[0.26λ g ]]> <![CDATA[a2]]> <![CDATA[0.31λ g ]]> <![CDATA[D L ]]> <![CDATA[0.3λ g ]]> <![CDATA[b2]]> <![CDATA[0.29λ g ]]> <![CDATA[LF L ]]> <![CDATA[0.51λ g ]]> g <![CDATA[0.07λ g ]]> <![CDATA[D R ]]> <![CDATA[0.68λ g ]]> <![CDATA[L1~L 16 ]]> <![CDATA[0.41λ g ]]> <![CDATA[LF R ]]> <![CDATA[1.41λ g ]]>

[0031] The above-mentioned millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna was tested and analyzed, and the far-field radiation diagram is shown in the following figure: Figures 4 to 6 As shown in the figure, Figure 4 The elevation and horizontal far-field radiation patterns of the antenna when the operating frequency is 36.1 GHz. Figure 5 The elevation and horizontal far-field radiation patterns of the antenna when the operating frequency is 36.3 GHz. Figure 6 is the far-field radiation diagram of the antenna in elevation and horizontal directions when the operating frequency is 36.5GHz; the impedance bandwidth is as follows Figure 7 As shown in the figure, it can be seen that the far-field forward-tilted radiation performance of the millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna provided by the present invention at each operating frequency point within its operating frequency band is relatively consistent, and a far-field radiation pattern with a deviation from the normal in the pitch direction of 19 degrees is obtained by adopting a non-end-fed form, and the pitch direction has a sidelobe level lower than -10dB, avoiding sidelobe interference; at the same time, the 3dB radiation angle in the horizontal direction is greater than 60°, which can meet a wider detection range in the horizontal direction and reduce the detection blind area.

[0032] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A millimeter-wave center-fed forward-tilted fan-beam microstrip array antenna, comprising: A dielectric substrate, a radiation array, a metal floor and a feeding structure; characterized in that the metal floor is arranged on the lower surface of the dielectric substrate, and the radiation array is arranged on the upper surface of the dielectric substrate; the radiation array comprises: a left radiation sub-array and a right radiation sub-array, the left radiation sub-array and the right radiation sub-array respectively adopt an end-fed line array structure, and the left radiation sub-array and the right radiation sub-array are fed in parallel by the feeding structure, so that the radiation array forms a middle-fed line array structure; The right radiation subarray is composed of a plurality of right microstrip array elements. Adjacent right microstrip array elements are connected in sequence through feeder lines. The length of the feeder lines is D R , and D R >λ g / 2,λ g is the medium wavelength, so that the far-field radiation elevation beam of the right radiating sub-array deviates from the antenna normal and deviates toward the load end; The left radiation subarray is composed of a plurality of left microstrip array elements. Adjacent left microstrip array elements are connected in sequence by feeder lines. The length of the feeder lines is D L , and D L <λ g / 2,λ g is the medium wavelength; so that the far-field radiation elevation beam of the left radiating subarray deviates from the antenna normal and tilts forward toward the feed end; The phases of the right radiation sub-array and the left radiation sub-array are superimposed in the direction of the preset forward tilt angle to obtain the forward tilt far-field radiation elevation beam pointing; In the right radiation subarray, a passive loading structure is respectively arranged between adjacent right microstrip array elements, the passive loading structure is composed of two upper and lower passive microstrip patches, the passive loading structure is arranged in the middle position between adjacent right microstrip array elements, and the two passive microstrip patches are symmetrically arranged on both sides of the feed line; In the left radiation subarray, decoupling structures are respectively arranged between adjacent left microstrip array elements, the decoupling structures are composed of two upper and lower grounded microstrip patches, the decoupling structures are arranged in the middle position between adjacent left microstrip array elements, and the two grounded microstrip patches are symmetrically arranged on both sides of the feed line.

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