Broadband millimeter wave circularly polarized microstrip slot antenna loaded with reflection cavity

Abstract

The invention discloses a broadband millimeter wave circularly polarized microstrip slot antenna loaded with a reflection cavity, and belongs to the technical field of radio frequency front-end devices. The main structure is composed of a power division phase shifter, a feed branch knot, a double-layer dielectric plate, a metal reflection cavity and a metal ground. The power division phase shifter structure of the antenna is composed of a Wilkinson power divider and a phase shifter. The metal ground is arranged between the double-layer dielectric plates, the center of the metal ground is provided with a square slotting pattern, and the square slotting pattern coincides with the center of the metal ground and rotates by 45 degrees; the microstrip feeder line is located on the lower surface of the lower dielectric plate; four corners of an inner cavity of the metal reflection cavity are chamfered, and the inner cavity is in central symmetry with the metal ground slotting pattern. The wide impedance bandwidth working characteristic from 25.12 Ghz to 32.31 Ghz can be achieved in the millimeter wave frequency band, the gain can reach 8.6 dBi when the antenna works at 26.5 Ghz, high gain is kept in the working frequency band, and the antenna structure is convenient to manufacture.

Description

Technical Field

[0001] The present invention discloses a design of a broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflection cavity, which is mainly applied to communication systems in the millimeter-wave band and other aspects, belonging to the field of radio frequency front-end devices. Background Art

[0002] Currently, modern communication technologies are developing rapidly, and the demand for radio frequency antenna devices with excellent performance is increasing continuously. Based on the structural optimization of the microstrip slot antenna, this design expands a broadband millimeter-wave circularly polarized microstrip slot antenna structure loaded with a reflection cavity. Due to its characteristics such as wide bandwidth, high gain, low back radiation, and high front-to-back ratio, it has important research significance in the fields of millimeter-wave communication systems, radio navigation, etc.

[0003] The electromagnetic radiation of the basic microstrip slot antenna model is bidirectional. When the antenna is aligned to radiate on one side, a considerable amount of electromagnetic energy radiates to the back side, showing a significant back lobe in the antenna radiation pattern and poor front-to-back ratio performance. Summary of the Invention

[0004] The above background art elaborates on some problems existing in millimeter-wave antennas. The present invention proposes a design of a broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflection cavity.

[0005] The present invention is realized through the following technical solutions:

[0006] A broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflection cavity includes a power divider phase shifter and a feeding stub, and the feeding stub is connected to the end of the power divider phase shifter; it also includes an upper dielectric plate 23, a lower dielectric plate 24, a metal reflection cavity 25, and a metal ground 22; the metal ground 22 structure is located between the upper dielectric plate 23 and the lower dielectric plate 24; the power divider phase shifter 1 and the feeding stub are both fixed on the lower surface of the lower dielectric plate 24;

[0007] The metal reflection cavity 25 is located directly below the lower dielectric plate 24, and there is an air layer between the lower dielectric plate 24 and the metal reflection cavity 25, and the four inner corners of the inner cavity 21 of the metal reflection cavity 25 are chamfered.

[0008] Further, the material of the upper dielectric plate 23 is RT5880.

[0009] Further, the material of the lower dielectric plate 24 is RT5880.

[0010] Further, a square opening is provided at the center of the metal ground 22, and the center of the metal ground, the center of the upper dielectric plate 23, the center of the lower dielectric plate 24, and the central axis of the metal reflection cavity are all located on the same vertical line.

[0011] Furthermore, the power divider phase shifter includes a first-stage power divider phase shifter and two second-stage power divider phase shifters; the two output terminals of the first-stage power divider are connected to the input terminals of the two second-stage power dividers, and the four output terminals of the two second-stage power dividers are respectively connected to the corresponding feeding branches.

[0012] Furthermore, the feeding branches are U-shaped metal strips; the four U-shaped metal strips all face inward, and two by two are opposite to form a cross-shaped frame; there is no contact between the feeding branches, and the included angle between adjacent feeding branches is 90°.

[0013] Furthermore, the projection of the cross-shaped frame on the metal ground is located within the area where the square opening is located.

[0014] Furthermore, the projection of the metal reflection cavity on the metal ground has its inner cavity partially covering the square opening.

[0015] Furthermore, the inner cavity 21 of the metal reflection cavity 25 is a cuboid cavity rotated 45 degrees; the cross-shaped frame and the square opening are both rotated 45° to face the inner cavity of the metal reflection cavity.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The present invention improves the microstrip slot antenna structure, loads a metal reflection cavity below the antenna structure, designs and optimizes its relative height and the geometric dimensions of the inner cavity, so that most of the electromagnetic waves radiated in the back direction are reflected back to the front direction, avoiding the consumption of electromagnetic energy, and the main lobe in the antenna radiation pattern is significantly superior to the back lobe, and the front-to-back ratio performance is good.

[0018] This antenna has many advantages such as a wide impedance bandwidth, high gain, and convenient manufacturing, and is suitable for the field of radio frequency communication systems with high requirements for the bandwidth of antenna elements.

[0019] a) The antenna structure is convenient to manufacture, and the antenna structure mainly uses two materials, copper and RT5880 dielectric substrate.

[0020] b) The impedance bandwidth performance of the antenna device is good, and a wide impedance bandwidth from 25.12 GHz to 32.31 GHz is achieved, providing a new excellent solution for millimeter-wave wireless communication applications.

[0021] c) The antenna device achieves high gain performance within the operating frequency band. Description of the Drawings

[0022] Figure 1 is the top view of the antenna structure;

[0023] Figure 2 is the front view of the antenna model;

[0024] Figure 3 It is the overall structure diagram of the antenna;

[0025] Figure 4 It is the top view of the microstrip line structure of the first-level power divider in the power divider phase shifter;

[0026] Figure 5 It is the top view of the microstrip line structure of the second-level power divider in the power divider phase shifter;

[0027] Figure 6 It is the top view of the feeding stub structure;

[0028] Figure 7 It is the reflection coefficient curve of the broadband millimeter-wave circularly polarized microstrip slot antenna;

[0029] Figure 8 It is the xoy plane pattern of the broadband millimeter-wave circularly polarized microstrip slot antenna at 25.5 GHz;

[0030] Figure 9 It is the xoy plane pattern of the broadband millimeter-wave circularly polarized microstrip slot antenna at 26.5 GHz;

[0031] Figure 10 It is the xoy plane pattern of the broadband millimeter-wave circularly polarized microstrip slot antenna at 30.5 GHz;

[0032] Figure 11 It is the axial ratio curve of the broadband millimeter-wave circularly polarized microstrip slot antenna. Detailed implementation manners

[0033] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0034] Referring to Figures 1 to 3 , in this embodiment, as a broadband millimeter-wave circularly polarized microstrip slot antenna with a loaded reflection cavity, the main structure includes a power divider phase shifter 1, an upper dielectric board 23, a lower dielectric board 24, a metal reflection cavity 25, a metal ground 22, and four feeding stubs (labeled 17, 18, 19, 20);

[0035] The metal ground 22 structure is located in the middle layer between the upper dielectric board 23 and the lower dielectric board 24; the metal parts of the power divider phase shifter 1 and the four feeding stubs (labeled 17, 18, 19, 20) are fixed on the lower surface of the lower dielectric board 24; the metal reflection cavity 25 is located directly below the lower dielectric board 24 with an air layer in between. And the four corners of the inner cavity 21 of the metal reflection cavity 25 are chamfered circularly.

[0036] The power divider phase shifter 1 includes a first-stage power divider phase shifter and two second-stage power divider phase shifters. The two output terminals of the first-stage power divider are connected to the input terminals of the two second-stage power dividers. The main structure of the first-stage power divider phase shifter includes a power divider 2 and a phase shifter 3. An isolation resistor 6 is provided inside the first-stage power divider, and two shorting vias (labeled 4, 5) are provided in the phase shifter. The main structure of the second-stage power divider phase shifter includes power dividers 7, 12 and phase shifters (labeled 8, 13).

[0037] Isolation resistors (labeled 11, 16) are provided inside the second-stage power divider, and shorting vias (labeled 9, 10, 14, 15) are provided in the phase shifter. Each second-stage power divider phase shifter controls two feeding stubs.

[0038] The metal parts of the power divider phase shifter 1 and the four feeding stubs are made of copper, and the copper plating thickness is 20 microns.

[0039] The material of the metal ground 22 is copper, and the copper plating thickness is 20 microns. Square openings are provided thereon, and the metal ground slotting pattern is the square opening.

[0040] The types of the upper dielectric substrate 23 and the lower dielectric substrate 24 are RT5880, and the material is polytetrafluoroethylene.

[0041] The material of the metal reflection cavity 25 is copper.

[0042] The materials of the 6 shorting vias (labeled 4, 5, 9, 10, 14, 15) are copper.

[0043] The power divider phase shifter 1 is a one-to-four power divider phase shifter. First, the input signal is processed by the first-stage power divider phase shifter and then two signals with a phase difference of 180° are output to the two second-stage power divider phase shifters. Then, each second-stage power divider phase shifter processes the signals and outputs two signals with a phase difference of 90° to the four feeding stubs. Finally, the phase differences of the four feeding stubs differ by 90° in sequence, and the antenna radiates circularly polarized electromagnetic waves.

[0044] In this embodiment, the dielectric substrate and the metal ground are both rectangular structures. The square opening on the metal ground is rotated 45° relative to the rectangular metal ground; the feeding stubs are U-shaped metal strips, and the four U-shaped metal strips are rotationally symmetric around the center. The openings of the U-shaped metal strips all face inward, forming a cross-shaped frame; the cross-shaped frame is located directly below the square opening, and the central axis of each U-shaped metal strip has an angle of 45° with the side of the square opening, adapting to the square opening.

[0045] This embodiment improves the microstrip slot antenna structure. The electromagnetic radiation of the basic microstrip slot antenna model is in both side directions. When the antenna is aligned to radiate on one side, a considerable amount of electromagnetic energy radiates to the back side, and significant back lobes appear in the antenna radiation pattern, and the front-to-back ratio performance is not good.

[0046] In this embodiment, a metal reflection cavity is loaded below the lower dielectric substrate 24, and the geometric dimensions of the inner cavity of the metal reflection cavity are designed and optimized, so that most of the electromagnetic waves radiated in the dorsal direction are reflected back to the front direction, avoiding the consumption of electromagnetic energy. The main lobe in the antenna radiation pattern is significantly superior to the back lobe, and the front-to-back ratio performance is good.

[0047] In this embodiment, the feeding of the antenna structure is carried out by a microstrip line. The microstrip feed line and the tuning stub couple electromagnetic energy to the metal ground structure loaded with a wide slot, and then radiate outward. In addition, the lower bottom edges of the four U-shaped feed stubs project onto the square opening of the metal ground. There is a certain horizontal distance between the lower bottom edges of the feed stubs and the four sides of the square opening, aiming to obtain good impedance matching for the antenna. There is a certain vertical distance between the lower surface of the lower dielectric substrate and the upper surface of the metal reflection cavity, aiming to obtain good impedance matching for the antenna.

[0048] In order to reduce energy loss, the metal material of the antenna structure is selected as copper material with low resistivity, and the material selected for the dielectric substrate is RT5880.

[0049] The self-geometric dimensions of each metal structure of the antenna structure and the spatial position relationship between two-by-two structures will have different degrees of influence on the resonant frequency, impedance bandwidth, and radiation pattern of the antenna. The specific manifestations are as follows:

[0050] a) Through continuous design of the length of the phase shifter in the power divider phase shifter, an ideal 90-degree phase difference is obtained between adjacent feed stubs. The change in the length of the phase shifter affects the feed phase difference, resulting in the deterioration of the radiation pattern.

[0051] b) During the process of increasing the depth of the inner cavity of the metal reflection cavity from 0, the impedance matching gradually improves. When it reaches the designed size, the impedance matching is ideal. Further increasing will gradually deteriorate the impedance matching.

[0052] c) The width of the microstrip line of the power divider phase shifter and the feed stubs is designed in combination with the thickness of the lower dielectric substrate. When using the designed size, the impedance matching is ideal. Increasing or decreasing the width of the microstrip line will cause the impedance matching to decline.

[0053] Therefore, it is of great significance to select reasonable phase shifter dimensions, inner cavity dimensions of the reflection cavity, and microstrip line dimensions to improve the performance of this microstrip slot antenna.

[0054] Here, a size combination is selected for example illustration. The following data units are micrometers:

[0055] Specifically refer to Figure 4 Among them, the dimensions of the structure are:

[0056] The structural lengths are as follows: a = 290; b = 500; c = 1750; d = 140; e = 260; f = 170; g = 455; h = 1472; i = 670; j = 310; k = 1540; l = 1905; m = 195; n = 940; o = 119; p = 281; q = 940; r = 1223; s = 1255.

[0057] Figure 5 The dimensions of the structure are:

[0058] For structure: t = 2671; u = 671; v = 2915; w = 12848; x = 2877; y = 855; z = 140; aa = 1750; ab = 260; ac = 455; ad = 1471; ae = 1166; af = 510; ag = 1971; ah = 1589; ai = 5996; aj = 4059; ak = 2695; al = 2568; am = 355; an = 195; ao = 940; ap = 281; aq = 119; ar = 1137; as = 860.

[0059] Figure 6 The dimensions of the structure are:

[0060] For structure: at = 12000; au = 10000; av = 252;

[0061] The thickness of the upper dielectric plate 23 is 175.

[0062] The thickness of the lower dielectric plate 24 is 100.

[0063] The thickness of the metal reflection cavity 25 is 2500.

[0064] An air layer with a thickness of 160 is provided between the lower dielectric plate 24 and the metal reflection cavity 25.

[0065] Appendix Figure 3 is the three-dimensional stereoscopic image of the overall structure of the antenna structure.

[0066] Appendix Figure 7 is the reflection coefficient of the antenna structure. The -10dB bandwidth is from 25.12Ghz to 32.31Ghz, having the characteristic of wide impedance bandwidth.

[0067] Appendix Figure 8It is the radiation pattern of the antenna structure in the phi = 0° plane when operating at a low frequency of 25.5 GHz, with a gain of 7.4 dB.

[0068] Appendix Figure 9 It is the radiation pattern of the antenna structure in the phi = 0° plane when operating at an intermediate frequency of 26.5 GHz, with a gain of 8.5 dB.

[0069] Appendix Figure 10 It is the radiation pattern of the antenna structure in the phi = 0° plane when operating at a high frequency of 30.5 GHz, with a gain of 8.0 dB.

[0070] Appendix Figure 11 It is the axial ratio frequency curve of the antenna structure.

[0071] The above is only one example. If you want to obtain an antenna structure operating at different frequencies, different antenna geometric dimensions can be adopted so as to be used in different application scenarios.

Claims

1. A broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity, comprising a power division phase shifter and a feeding branch, wherein the feeding branch is connected to the end of the power division phase shifter; characterized in that: It also includes an upper dielectric plate (23), a lower dielectric plate (24), a metal reflection cavity (25) and a metal ground (22); the metal ground (22) structure is located between the upper dielectric plate (23) and the lower dielectric plate (24); the power division phase shifter (1) and the feeding branch are both fixed to the lower surface of the lower dielectric plate (24); The metal reflection cavity (25) is located directly below the lower dielectric plate (24), an air layer is provided between the lower dielectric plate (24) and the metal reflection cavity (25), and the four inner corners of the inner cavity (21) of the metal reflection cavity (25) are chamfered.

2. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 1, characterized in that: The material of the upper dielectric plate (23) is RT5880.

3. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 1, characterized in that: The material of the lower dielectric plate (24) is RT5880.

4. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 1, characterized in that: A square opening is provided at the center of the metal ground (22), and the center of the metal ground, the center of the upper dielectric plate (23), the center of the lower dielectric plate (24) and the central axis of the metal reflection cavity are all located on the same vertical line.

5. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 1, characterized in that: The power division phase shifter includes a primary power division phase shifter and two secondary power division phase shifters; The two output ends of the primary power divider are connected to the input ends of the two secondary power dividers, and the four output ends of the two secondary power dividers are respectively connected to corresponding feeding branches.

6. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 1, characterized in that: The feeding branches are U-shaped metal strips; the four U-shaped metal strips are all facing inwards, and two by two are opposite to each other to form a cross-shaped frame; there is no contact between the feeding branches, and the angle between adjacent feeding branches is 90°.

7. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 6, characterized in that: The projection of the cross-shaped frame on the metal ground is located in the area where the square opening is located.

8. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 4, characterized in that: The projection of the metal reflective cavity on the metal ground has an inner cavity part covering the square opening.

9. The broadband millimeter-wave circularly polarized microstrip slot antenna loaded with a reflective cavity according to claim 1, characterized in that: The inner cavity (21) of the metal reflective cavity (25) is a rectangular cavity rotated 45 degrees; the cross-shaped frame and the square opening are both rotated 45 degrees to face the inner cavity of the metal reflective cavity.

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