Gap waveguide-fed millimeter-wave microstrip antenna element and array antenna

Abstract

The present invention discloses a millimeter-wave microstrip antenna unit and an array antenna fed by a slot waveguide. The antenna unit includes a metal bottom plate, and a plurality of metal pins are formed on the upper surface of the metal bottom plate. A ridge slot waveguide is formed between the metal pins near the middle. An upper metal plate is disposed on the upper surface of the metal pins. A coupling hole is formed at the center of the upper metal plate, and the inner end of the ridge slot waveguide is located below the coupling hole. A dielectric layer is formed on the upper surface of the upper metal plate, and a plurality of radiation patches are formed on the upper surface of the dielectric layer. The radiation patches are interconnected by microstrip lines, and the microstrip lines are located above the coupling hole. The array antenna has the advantages of convenient mechanical assembly, low cost, high gain, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of millimeter-wave antennas, and in particular, to a gap waveguide-fed millimeter-wave microstrip antenna element and an array antenna. Background Art

[0002] In recent years, due to the demand for high-data-rate short-range wireless communication, the development of 60 GHz millimeter-wave wireless communication systems has increased. The main challenge in the 60 GHz band is the very high radio wave absorption caused by oxygen molecule resonance. As a candidate solution method, it is to use high-gain antennas with high radiation efficiency. In recent years, the development of high-gain broadband millimeter-wave antenna arrays with high radiation efficiency has attracted increasing attention. Different planar antenna arrays, such as microstrip and substrate integrated waveguide (SIW) arrays and slot antenna arrays, are two main technologies for millimeter-wave applications. The low efficiency of microstrip and SIW antenna arrays brings many limitations to their practical millimeter-wave applications. A main aspect restricting the achievable gain of these antenna arrays is the loss in the feeding network. In fact, to achieve a high-gain array antenna in the millimeter-wave band requires a low-loss feeding network. As a common candidate, the feeding waveguide slot array has been used to achieve high gain and efficiency. At high frequencies, these antennas require precise, high-precision, and expensive manufacturing. Summary of the Invention

[0003] The technical problem to be solved by the present invention is how to provide a gap waveguide-fed millimeter-wave microstrip antenna element and an array antenna that are convenient for mechanical assembly, have low cost, and high gain.

[0004] To solve the above technical problem, the technical solution adopted by the present invention is: A gap waveguide-fed millimeter-wave microstrip antenna element, characterized in that: it includes a metal bottom plate, and a plurality of metal pins are formed on the upper surface of the metal bottom plate. A ridge gap waveguide is formed between the metal pins near the middle. The ridge gap waveguide is fixed on the upper surface of the metal bottom plate, and the inner end of the ridge gap waveguide is located in the middle of the metal bottom plate, and the outer end of the ridge gap waveguide is located at the edge part of the metal bottom plate. An upper metal plate is provided on the upper surface of the metal pins. A coupling hole is formed in the center of the upper metal plate, and the inner end of the ridge gap waveguide is located below the coupling hole. A dielectric layer is formed on the upper surface of the upper metal plate, and a plurality of radiation patches are formed on the upper surface of the dielectric layer. The radiation patches are interconnected by microstrip lines, and the microstrip lines are located above the coupling hole.

[0005] A further technical solution lies in that: the height of the ridge gap waveguide is less than the height of the metal pins.

[0006] A further technical solution lies in that: the upper metal plate is fixedly connected to the metal bottom plate through support columns, so that an air gap is formed between the upper metal plate and the upper surface of the metal pin.

[0007] Preferably, the air gap is 0.05 mm.

[0008] A further technical solution lies in that: the overall shape of the radiation patch is rectangular, and the four radiation patches are arranged in a circular shape. An extension part is formed inside each radiation patch, and the extension parts are interconnected through the microstrip lines.

[0009] A further technical solution lies in that: the microstrip line includes a central feeder line in the middle and lateral feeder lines at both ends of the central feeder line. There are four lateral feeder lines, which are respectively connected to the extension parts on each radiation patch.

[0010] A further technical solution lies in that: the dielectric plates between the coupling holes and the extension parts are arranged oppositely.

[0011] Preferably, the length of the radiation patch is 1.6 mm, the width is 1.25 mm, and the thickness is 18 μm. The center distance between adjacent radiation patches is 2.45 mm in both the x and y directions.

[0012] The present invention also discloses a gap waveguide-fed millimeter-wave microstrip array antenna, which is characterized in that: it includes 16 of the above-mentioned millimeter-wave microstrip antenna units, and the connection between the antenna units is realized by connecting to the ridge gap waveguide in the antenna unit through a power divider.

[0013] A further technical solution lies in that: a via hole is formed in the center of the metal bottom plate in the array antenna, and an input waveguide is formed in the via hole. The input waveguide is connected to the power divider, and the input signal is distributed to the ridge gap waveguide in the antenna unit through the power divider for transmission.

[0014] The beneficial effects of adopting the above technical solutions are as follows: in the array antenna of the present application, a waveguide can be realized without the need for metal contact between the upper surface (metal pin) and the lower surface (upper metal plate), which simplifies the antenna with a mechanical assembly design, thereby reducing the production cost of the antenna. In addition, the array antenna of the present application is tested through experiments. When the operating frequency is 57.5–67.2 GHz, it has an impedance bandwidth of 15.5%, the reflection coefficient is lower than -10 dB, the gain is higher than 21.5 dBi, the side lobe levels in the E-plane and H-plane are lower than -13 dB, and the antenna array fed by RGW can be widely applied to microstrip antennas. Description of the Drawings

[0015] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0016] Figure 1 It is a schematic structural diagram of the antenna unit according to an embodiment of the present invention;

[0017] Figure 2 It is a schematic structural diagram of the central feeder and the lateral feeder in an embodiment of the present invention

[0018] Figure 3 It is a side view of the antenna unit according to an embodiment of the present invention;

[0019] Figure 4 It is a reflection coefficient curve graph of the antenna unit according to an embodiment of the present invention;

[0020] Figure 5 It is a partially sectional structural schematic diagram of the array antenna according to an embodiment of the present invention;

[0021] Figure 6 is Figure 5 An enlarged structural schematic diagram at position A in;

[0022] Figure 7 It is the simulation and measurement of |S11| of the antenna array in an embodiment of the present invention

[0023] Figure 8 It is a simulation directivity and measurement gain curve graph of the array antenna and the 100%, 90%, 80% and 70% efficiency lines in an embodiment of the present invention;

[0024] Figure 9a It is the radiation pattern (E-plane - 58 GHz) of the array antenna in an embodiment of the present invention;

[0025] Figure 9b It is the radiation pattern (H-plane - 58 GHz) of the array antenna in an embodiment of the present invention;

[0026] Figure 9c It is the radiation pattern (E-plane - 62 GHz) of the array antenna in an embodiment of the present invention;

[0027] Figure 9d It is the radiation pattern (H-plane - 62 GHz) of the array antenna in an embodiment of the present invention;

[0028] Figure 9e It is the radiation pattern (E-plane - 67 GHz) of the array antenna in an embodiment of the present invention;

[0029] Figure 9f It is the radiation pattern (H-plane - 67 GHz) of the array antenna in an embodiment of the present invention;

[0030] Wherein: 1. Metal bottom plate; 2. Metal pin; 3. Ridge gap waveguide; 4. Upper metal plate; 5. Coupling hole; 6. Dielectric layer; 7. Radiation patch; 8. Air gap; 9. Central feeder; 10. Lateral feeder; 11. Power divider; 12. Input waveguide. Specific embodiments

[0031] Combined with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0033] As Figures 1-3 shown, the embodiment of the present invention discloses a gap waveguide-fed millimeter-wave microstrip antenna unit, including a metal bottom plate 1, on the upper surface of the metal bottom plate 1, a plurality of metal pins 2 are formed, and the specific number of the metal pins 2 can be set according to needs; a ridge gap waveguide 3 is formed between the metal pins 2 near the middle, the ridge gap waveguide 3 is fixed on the upper surface of the metal bottom plate 1, and the inner end of the ridge gap waveguide 3 is located in the middle of the metal bottom plate 1, and the outer end of the ridge gap waveguide 3 is located at the edge part of the metal bottom plate 1; an upper metal plate 4 is arranged on the upper surface of the metal pin 2, a coupling hole 5 is formed in the center of the upper metal plate 4, and the inner end of the ridge gap waveguide 3 is located below the coupling hole 5, a dielectric layer 6 is formed on the upper surface of the upper metal plate 4, a plurality of radiation patches 7 are formed on the upper surface of the dielectric layer 6, the radiation patches 7 are interconnected by microstrip lines, and the microstrip lines are located above the coupling hole 5.

[0034] As Figure 1 shown, the height of the ridge gap waveguide 3 is less than the height of the metal pin 2. The upper metal plate 4 is fixedly connected to the metal bottom plate 1 through support columns, so that an air gap 8 is formed between the upper metal plate 4 and the upper surface of the metal pin 2. Preferably, the air gap 8 can be 0.05 mm. Further, as Figure 1As shown, the overall shape of the radiation patch 7 is rectangular, and the four radiation patches 7 are arranged in a circular pattern. An extension part is formed inside each radiation patch 7, and the extension parts are interconnected through the microstrip line. The microstrip line includes a central feeder 9 located in the middle and lateral feeders 10 located at both ends of the central feeder 9. There are four lateral feeders 10, which are respectively connected to the extension parts on each radiation patch 7. Preferably, the length of the radiation patch 7 is 1.6 mm, the width is 1.25 mm, and the thickness is 18 μm. The center-to-center spacing between adjacent radiation patches 7 is 2.45 millimeters in both the x and y directions (0.49 λ at 60 GHz 0 ).

[0035] Therefore, the problems associated with grating lobes will be much smaller than those of other leaky-waveguide slot arrays. The microstrip patch is a narrowband resonant structure. There are many available techniques to increase the bandwidth of microstrip patch antennas. To expand the bandwidth, coupling slots are used to feed the central feeder of the patch. Due to a large number of design parameters, aperture-coupled feeding provides greater radiation pattern symmetry and is easier to design for a larger impedance bandwidth.

[0036] The microstrip patch is a narrowband resonant structure. To expand the bandwidth, coupling slots are used to feed the central feeder of the patch. Aperture-coupled feeding provides a better symmetric radiation pattern, and due to a large number of design parameters, a larger impedance bandwidth is easier to design. In this application, the topology of a microstrip T-junction is used to distribute power, and a microstrip T-junction with broadband characteristics is used to distribute power. Therefore, by appropriately designing the length and width of the aperture and the width of the central feeder, a wider impedance match is achieved. The lower layer contains some metal pins and ridges to form an RGW distribution network. Periodic metal pins are planted on both sides of the ridges to generate the required stopband characteristics and prevent waves from propagating in unwanted directions. The pin size is selected to achieve a cutoff bandwidth of 40 GHz - 100 GHz. As shown in Figure 3, there is a very small air gap between the top surface of the metal pin 2 and the upper metal plate 4, so no electrical contact is required between them. The RGW feeding structure excites the coupling slots etched in the substrate ground plane. By optimizing the sizes of the coupling slots and the microstrip feeders, the four patches can be excited with the same amplitude and phase. Note that the four radiation patches have the same electric field phase and amplitude, indicating that the subarray has a maximum in the broadside direction.

[0037] The designed antenna element has dimensions of 4.9 × 4.9 mm in the x and y directions 2 . The applied infinite array method includes mutual coupling between subarrays. As Figure 4 shown, the reflection coefficient of the antenna element shows that the bandwidth with |S11| < -10 dB is 56.5 - 66 GHz (15.5%).

[0038] In this application, an aperture-coupled microstrip antenna array fed by a ridge gap waveguide (RGW) feed network in the 60 GHz band is studied. An array of 16 antenna elements is designed and simulated. The main advantage is that, compared with a three-layer slot array including a feed network, a cavity layer, and a radiation slot layer, this structure can maintain a two-layer planar profile. The size of the proposed antenna element is 4.9 mm (0.98λ0)×4.9 mm (0.98λ0), and if scanning is required, it is less than 8.8 mm (1.76λ0)×8.8 mm (1.76λ0) within a limited range. In addition, a 4×4 array antenna proposed in this application has an impedance bandwidth of 15.5% at the operating frequency (57.5 - 67.2 GHz), with a reflection coefficient lower than -10 dB, a gain higher than 21.5 dBi, and sidelobe levels in the E- and H-planes lower than -13 dB. The simulation and measurement results show that the proposed array antenna has high gain and high efficiency for 60 GHz applications. The metal feed network can be easily manufactured by computer numerical control (CNC) milling, shaping, or electrical discharge machining.

[0039] For high-gain applications, an antenna array with 4×4 is designed, as shown in Figure 5. The synthetic feed network is realized by interconnecting T-junction power dividers. In the lower layer, an RGW power divider is designed to feed 16 array antennas in the upper layer through 16 rectangular coupling slots. The feed network is designed based on a quarter-wave impedance transformer and a matching T-junction.

[0040] Specifically, as Figures 5-6 shown, the present invention also discloses a gap waveguide-fed millimeter-wave microstrip array antenna, including 16 of the millimeter-wave microstrip antenna elements. The connection between the antenna elements is realized by connecting the ridge gap waveguide in the antenna element through a power divider 11. A via hole is formed in the center of the metal bottom plate 1 of the array antenna, and an input waveguide 12 is formed in the via hole. The input waveguide 12 is connected to the power divider 11, and the input signal is distributed to the ridge gap waveguide 3 in the antenna element through the power divider 11 for transmission.

[0041] For measurement purposes, a broadband compact transition is designed between the input waveguide and the ridge gap waveguide 3 (RGW), as Figure 6As shown. At the end of the ridge gap waveguide 3, two steps are used, which enables the mode of the RGW to be converted to the TE10 mode of the rectangular waveguide. The transition is designed and optimized to achieve minimum reflection and insertion loss in the operating frequency band. Due to the differential output provided by the transition in the two ridge gap waveguides 3, the left and right sides of the feeding layer are mirrored. The input power of the input waveguide excites the antenna through the designed transition, and then flows through the RGW 16-way power divider. To achieve ideal matching, all parameters of the transition, power divider, and microstrip structure are optimized.

[0042] The designed array antenna is fabricated by standard CNC milling technology. To experimentally verify the operation of the array antenna, the array antenna is fed by a standard rectangular waveguide. The measurements of S11, gain, and radiation pattern are performed by a millimeter-wave vector network analyzer in an outdoor test range measurement system. The simulated and measured input reflection coefficients of the antenna array are shown in Fig. 7. The measured bandwidth of |S11| < -10 dB is 15.5% of 57.5 - 67.2 GHz. The difference between the measurement results and the simulation results is due to manufacturing tolerances and assembly tolerances. Fig. 8 shows the frequency characteristics such as the directivity, gain, and aperture efficiency of the antenna. However, the difference between the measured gain and the simulated directivity results is less than 1 dB. This difference is partly caused by the deviation of the dielectric, the metal loss in the simulation and measurement setups, and the tolerance of manufacturing the antenna. In the operating frequency band, the total radiation efficiency of the antenna array is still higher than 75%. The difference between the simulated and measured values at 60 - 61 GHz is considered to be ±0.25 dB or approximately 0.5 dB of measurement uncertainty due to the use of a standard gain horn in the measurement chamber. Figs. 9a - 9f show the simulated and measured normalized radiation patterns in the E-plane and H-plane at 67 GHz. The main reason for the small difference is measurement uncertainty. The radiation pattern of the 3 dB beamwidth measured at 62 GHz is approximately 13° and 15° in the E-plane and H-plane, respectively. In addition, the maximum sidelobe level measured at 62 GHz is -13.5 dB, the front-to-back ratio is better than 25 dB, and the cross-polarization level along the antenna axis is -28 dB.

[0043] In summary, the array antenna described in this application has an impedance bandwidth of 15.5% at the operating frequency (57.5 - 67.2 GHz), a reflection coefficient lower than -10 dB, a gain higher than 21.5 dBi, sidelobe levels in the E-plane and H-plane lower than -13 dB, and the antenna array fed by the RGW can be widely applied to microstrip antennas.

Claims

1. A millimeter-wave microstrip antenna unit fed by a gap waveguide, characterized in that: It includes a metal bottom plate (1), and a plurality of metal pins (2) are formed on the upper surface of the metal bottom plate (1). A ridge gap waveguide (3) is formed between the metal pins (2) near the middle. The ridge gap waveguide (3) is fixed on the upper surface of the metal bottom plate (1), and the inner end of the ridge gap waveguide (3) is located in the middle of the metal bottom plate (1), and the outer end of the ridge gap waveguide (3) is located at the edge part of the metal bottom plate (1). An upper metal plate (4) is arranged on the upper surface of the metal pin (2), a coupling hole (5) is formed in the center of the upper metal plate (4), and the inner end of the ridge gap waveguide (3) is located below the coupling hole (5). A dielectric layer (6) is formed on the upper surface of the upper metal plate (4), and a plurality of radiation patches (7) are formed on the upper surface of the dielectric layer (6). The radiation patches (7) are interconnected by microstrip lines, and the microstrip lines are located above the coupling hole (5); the height of the ridge gap waveguide (3) is less than the height of the metal pin (2); the length of the radiation patch (7) is 1.6 mm, the width is 1.25 mm, and the thickness is 18 μm. The center distance between adjacent radiation patches (7) is 2.45 mm in both the x and y directions; the upper metal plate (4) is fixedly connected to the metal bottom plate (1) through support columns, so that an air gap (8) is formed between the upper metal plate (4) and the upper surface of the metal pin (2).

2. The millimeter-wave microstrip antenna unit fed by a gap waveguide according to claim 1, characterized in that: The air gap (8) is 0.05 mm.

3. The millimeter-wave microstrip antenna unit fed by a gap waveguide according to claim 1, characterized in that: The whole of the radiation patch (7) is rectangular, and the four radiation patches (7) are arranged in a circular shape. An extension part is formed inside each radiation patch (7), and the extension parts are interconnected by the microstrip lines.

4. The millimeter-wave microstrip antenna unit fed by a gap waveguide according to claim 3, characterized in that: The microstrip line includes a central feeder (9) located in the middle and lateral feeders (10) located at both ends of the central feeder (9). There are four lateral feeders (10), which are respectively connected to the extension parts on each radiation patch (7).

5. The millimeter-wave microstrip antenna unit fed by a gap waveguide according to claim 3, characterized in that: The dielectric layer (6) between the coupling hole (5) and the extension part is arranged opposite to each other.

6. A millimeter-wave microstrip array antenna fed by a gap waveguide, characterized in that: It includes 16 millimeter-wave microstrip antenna units according to any one of claims 1-5, and the connection between the antenna units is realized by connecting the ridge gap waveguides in the antenna units through a power divider (11).

7. The millimeter-wave microstrip array antenna fed by a gap waveguide according to claim 6, characterized in that: A via hole is formed at the center of the metal bottom plate (1) in the array antenna, and an input waveguide (12) is formed in the via hole. The input waveguide (12) is connected to the power divider (11), and the input signal is distributed to the ridged slot waveguide (3) in the antenna element through the power divider (11) for transmission.

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