A millimeter-wave microstrip planar array antenna with low cross-polarization

Abstract

The present invention discloses a low cross-polarization millimeter-wave microstrip flat-panel array antenna, characterized in that it comprises: a dielectric substrate, a first printed microstrip circuit and a second printed microstrip circuit respectively arranged on the front and back surfaces of the dielectric substrate, and a rectangular metal waveguide fixed to the back surface of the dielectric substrate for feeding; the first printed microstrip circuit is composed of a longitudinal power division circuit, a transverse power division circuit cascaded to the longitudinal power division circuit, and a radiating rectangular patch unit connected to the transverse power division circuit. The present invention realizes a high-gain microstrip antenna array using only one layer of dielectric substrate by designing a microstrip power division circuit of a specific shape and combining it with a corresponding radiating rectangular patch unit, and effectively reduces the main polarization sidelobe envelope of the antenna, suppressing the high cross-polarization level of the traditional microstrip antenna array. According to simulation experiments, the millimeter-wave microstrip flat-panel array antenna provided by the present invention has the advantages of high gain, planarization, low cross-polarization, and easy mass production.

Description

Technical Field

[0001] The invention relates to the field of antenna design, and in particular to a high-gain millimeter-wave microstrip flat-panel array antenna with low cross polarization. Background Art

[0002] High-gain antennas are the front end of modern wireless microwave communications and have an important impact on the overall communication quality. Traditional high-gain microwave antennas include parabolic antennas and variations of parabolic antennas such as Cassegrain antennas and Gregorian antennas. However, with the refinement and differentiation of modern communications, traditional microwave antennas can no longer meet some application scenarios. For example, in urban scenarios, high-gain antennas are required to have low-profile and planar properties to achieve an overall beautiful appearance, and traditional parabolic antennas cannot meet the requirements.

[0003] In order to reduce the profile of the antenna and realize a planar antenna array, metal waveguide slot antennas, open metal waveguide antennas, printed array antennas, and microstrip antenna array antennas can be used. Antennas made of metal waveguide materials have the advantages of low loss and wide bandwidth, but their machining process is complex, production efficiency is low, and cost is high; printed array antennas require a supporting structure, and the structural design of the planar array is relatively complex, which is not suitable for use in millimeter wave bands that have strict requirements on structural errors. Microstrip antenna arrays can use planar printed circuit (PCB) technology, which has high machining accuracy and low cost, and is suitable for the design and production of millimeter wave high-gain antennas.

[0004] One of the drawbacks of microstrip patch antenna arrays is that they have high cross-polarization, which limits their application in scenarios with strict cross-polarization requirements. In order to reduce their cross-polarization, slot-coupled patch antennas can be used, but this method requires lamination of multiple dielectric boards, which increases the difficulty of processing and the cost.

[0005] Based on the above background, in practical applications, there is an urgent need for a millimeter-wave microstrip flat-panel array antenna with low cross-polarization to meet the requirements of some scenarios in modern communication systems for antennas with high gain, low cross-polarization, and easy mass production. Summary of the invention

[0006] The purpose of the present invention is to provide a millimeter wave microstrip flat panel array antenna which is high-gain, planar, low cross-polarization and easy to mass-produce.

[0007] In order to achieve the above object, the present invention adopts the following technical solution.

[0008] A low cross-polarization millimeter-wave microstrip planar array antenna, characterized in that it includes: a dielectric substrate, a first printed microstrip circuit and a second printed microstrip circuit respectively arranged on the front and back surfaces of the dielectric substrate, and a rectangular metal waveguide fixed to the back surface of the dielectric substrate for feeding; the first printed microstrip circuit is composed of a longitudinal power division circuit, a transverse power division circuit cascaded to the longitudinal power division circuit, and a radiating rectangular patch unit connected to the transverse power division circuit.

[0009] More preferably, the second printed microstrip circuit is a metal floor printed on the back of the dielectric substrate, and a rectangular gap is provided in the center of the metal floor; the rectangular metal waveguide is fixed at the center of the dielectric substrate, and the electromagnetic energy fed from the rectangular metal waveguide is coupled to the first printed microstrip circuit through the rectangular gap.

[0010] More preferably, an input microstrip segment corresponding to the rectangular gap is provided at the center position of the front surface of the dielectric substrate, and two of the longitudinal power dividing circuits are respectively connected to the upper and lower sides of the input microstrip segment.

[0011] More preferably, a plurality of the transverse power dividing circuits are cascaded outside each of the longitudinal power dividing circuits, and the transverse power dividing circuits and the radiating rectangular patch units are symmetrical along the longitudinal center line and the transverse center line of the dielectric substrate.

[0012] More preferably, a coupling microstrip segment for coupling and exciting the rectangular radiation patch unit is provided on the lateral power division circuit, and the coupling microstrip segment is spaced apart from the rectangular radiation patch unit and is coupled and excited via a gap.

[0013] More preferably, a metallized through hole is provided at the center of the coupling microstrip segment, and the metallized through hole electrically connects the coupling microstrip segment with the second printed microstrip circuit.

[0014] More preferably, the spacing between the horizontal power division circuits at each level is equal.

[0015] More preferably, a plurality of the radiating rectangular patches of the same size are connected to each level of the lateral power division circuit, and the spacing between two adjacent radiating rectangular patches is equal.

[0016] More preferably, the conversion segment width of the longitudinal power division circuit is designed according to the Taylor amplitude distribution required for sidelobe suppression, and the conversion segment width of the transverse power division circuit is the same as that of the longitudinal power division circuit, and the same Taylor amplitude distribution design is used.

[0017] More preferably, the operating frequency band of the millimeter wave microstrip planar array antenna is designed between 22-30 GHz.

[0018] The beneficial effects that can be achieved by the present invention using the above technical solution are:

[0019] By designing a microstrip power divider circuit of a specific shape and combining it with the corresponding radiating rectangular patch unit, a high-gain microstrip antenna array is realized using only one layer of dielectric substrate, and the main polarization sidelobe envelope of the antenna is effectively reduced, suppressing the high cross-polarization level of the traditional microstrip antenna array. Through simulation, processing and experimental testing, the millimeter-wave microstrip flat array antenna provided by the present invention has the advantages of high gain, planarization, low cross-polarization, and easy mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic top view of the structure of an antenna according to an embodiment of the present invention.

[0021] Figure 2 It is a schematic left view of the structure of the antenna of the present invention.

[0022] Figure 3 It is a schematic rear view of the structure of the antenna of the present invention.

[0023] Figure 4 It is a schematic diagram of the longitudinal microstrip power division circuit of the antenna of the present invention.

[0024] Figure 5 FIG. 1 is a schematic diagram of one row of transverse unit linear arrays of the antenna of the present invention.

[0025] Figure 6 It is a unit schematic diagram of the antenna of the present invention.

[0026] Figure 7 It is a return loss frequency curve diagram of the antenna of the present invention.

[0027] Figure 8 The graph is a graph showing how the gain of the antenna of the present invention varies with frequency.

[0028] Fig. 9 is the electric field radiation pattern of the center frequency of the antenna of the present invention.

[0029] Fig.10 It is the magnetic field surface radiation pattern of the center frequency of the antenna of the present invention.

[0030] Description of reference numerals:

[0031] 1: first printed microstrip circuit, 2: dielectric substrate, 3: rectangular metal waveguide, 4: second printed microstrip circuit.

[0032] 111: longitudinal power division circuit, 112: transverse power division circuit, 121: radiating rectangular patch unit, 113: coupled microstrip segment, 201: metallized through hole, 401: rectangular gap. DETAILED DESCRIPTION

[0033] In the description of the present invention, it should be noted that directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating directions and positional relationships are based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of narrating the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of the present invention.

[0034] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. Therefore, the definition of "first" and "second" features can explicitly or implicitly include one or more of the features. In the description of the present invention, "at least" means one or more, unless otherwise clearly and specifically defined.

[0035] In the present invention, unless otherwise specified and limited, the terms "assemble", "connect", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can also be a mechanical connection; it can be directly connected, or it can be connected through an intermediate medium, or the two elements can be internally connected. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the invention, unless otherwise specified and limited, a first feature being “above” or “below” a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being “above”, “below”, and “above” a second feature includes that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “above”, “below”, and “below” a second feature includes that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0037] The following is a further description of the specific implementation of the present invention in conjunction with the drawings of the specification, so that the technical solution and its beneficial effects of the present invention are clearer and more explicit. The following description of the embodiments with reference to the drawings is exemplary and intended to explain the present invention, but cannot be understood as limiting the present invention.

[0038] Additional aspects and advantages of the present invention will become apparent from the following description or may be learned by practice of the present invention.

[0039] See also Figure 1 and Figure 2 As shown, a low cross-polarization millimeter-wave microstrip flat-panel array antenna comprises: a dielectric substrate 2, a first printed microstrip circuit 1 and a second printed microstrip circuit 4 respectively arranged on the front and back sides of the dielectric substrate 2, and a rectangular metal waveguide 3 for feeding. The first printed microstrip circuit 1 is composed of a longitudinal power division circuit 111, a transverse power division circuit 112 cascaded to the longitudinal power division circuit 111, and a radiating rectangular patch unit 121 connected to the transverse power division circuit 112. By adjusting the width of each transformation segment of the longitudinal power division circuit 111 and the transverse power division circuit 112, the amplitude and phase of the electromagnetic wave reaching each radiating rectangular patch unit 121 can be controlled, thereby realizing the control of the pattern envelope and reducing the pattern side lobes.

[0040] See also Figure 3 As shown, the rectangular metal waveguide 3 is fixed to the center of the dielectric substrate 2, and the fixing method can be screws or the like. The floor of the second printed microstrip circuit 4 printed on the bottom surface of the dielectric plate 2 basically covers the bottom surface, and there is a rectangular gap 401 without copper at the center of the second printed microstrip circuit 4. The electromagnetic energy fed by the waveguide can be coupled to the first printed microstrip circuit 1 on the front of the dielectric substrate 2 through the rectangular gap 401, and the standing wave of the antenna can be adjusted by adjusting the size of the rectangular gap 401.

[0041] See also Figure 4 As shown, the longitudinal power division circuit 111 connects the input microstrip segment and each level of transverse power division circuits 112. By adjusting the width of each transformation segment of the longitudinal power division circuit 111, the longitudinal power distribution ratio can be controlled, thereby controlling the directional pattern envelope in this direction.

[0042] See also Figure 5 As shown, the horizontal power division circuit 112 connects the output end of the vertical power division circuit 111 and the input end of each radiating rectangular patch unit 121. By adjusting the width of each transformation segment of the horizontal power division circuit 112, the power distribution ratio in the horizontal direction can be controlled, thereby controlling the directional pattern envelope in this direction.

[0043] See also Figure 6As shown, the excitation mode of the radiating rectangular patch unit 121 is adjacent coupling, and the patch 121 has no direct electrical connection with the transverse power divider 112. The radiating rectangular patch unit 121 is excited by coupling through the coupling microstrip segment 113 extending from the transverse circuit 112, and through the gap between the coupling microstrip segment 113 and the radiating rectangular patch unit 121. The metallized through hole 201 is located at the center of the coupling microstrip segment 113, and the dielectric substrate 2 is opened and metallized at this position to realize the electrical connection between the coupling microstrip segment 113 and the second printed microstrip circuit 4 on the bottom surface. By adjusting the size of the radiating rectangular patch unit 121 and the coupling microstrip segment 113, the desired resonant radiation frequency can be achieved, and the cross polarization of this frequency band can be suppressed.

[0044] According to one embodiment of the present application, a microstrip planar array antenna is designed to operate at 27GHz, and the rectangular metal waveguide 3 is selected as a standard rectangular waveguide BJ260, with an internal length of 8.636mm and a width of 4.318mm. The size of the dielectric substrate 2 is 140mm×140mm, the relative dielectric constant of the dielectric material is 3.0, and the thickness is 0.78mm. The longitudinal power divider circuit 111 has 9 output terminals on one side, and the longitudinal periodic distance between the output terminals is 7.2mm; its transformation section width varies between 0.5mm and 1mm according to the Taylor amplitude distribution design with sidelobe suppression of -35dB. The transverse power divider circuit 112 also has 9 output terminals, and the periodic distance between the output terminals is 7.2mm; its transformation section width is the same as the longitudinal power divider, and the same Taylor amplitude distribution design is used. The length of the coupled microstrip segment 113 is 1.45mm and the width is 0.5mm. The diameter of the metallized through hole 201 is 0.4mm. The length of the radiating rectangular patch unit 121 is 4.8 mm and the width is 3 mm. The gap spacing between the radiating rectangular patch unit 121 and the coupling microstrip segment 113 is 0.2 mm. Through this design and optimization, the appropriate power divider size and unit size design are selected, so that the antenna array can achieve high gain and lower sidelobe beam envelope, and can achieve a lower cross-polarization level.

[0045] In order to better reflect the effect of the present invention, the samples prepared in the above embodiments are tested experimentally. The results are as follows: Figure 7-Figure 10 shown.

[0046] See also Figure 7 As shown in FIG. 1 , it is a return loss frequency curve of the above sample. From the figure, it can be seen that the antenna achieves a return loss performance of less than -10dB between 26 and 28GHz, and has good standing wave characteristics.

[0047] See also Figure 8As shown in FIG. 1 , which is a curve diagram of the gain of the above sample changing with frequency, it can be seen from the figure that the antenna achieves an antenna gain of more than 26 dB between 26.5 and 27.5 GHz, achieving a relatively high gain and maintaining a certain gain bandwidth.

[0048] See also Fig. 9 As shown in the figure, it is the electric field radiation pattern of the center frequency of the above sample, including the main polarization and cross polarization, and gives the envelope limit required by the Class 2 standard in this frequency band according to ETSI EN 302 217-4. From the figure, it can be seen that the main polarization and cross polarization of the antenna in the electric field are both within the required envelope, achieving good sidelobe envelope suppression.

[0049] See also Fig.10 As shown in the figure, it is the magnetic field plane radiation pattern of the center frequency of the above sample, including the main polarization and cross polarization, and gives the envelope limit required by the Class 2 standard in this frequency band according to ETSI EN 302 217-4. From the figure, it can be seen that the main polarization and cross polarization of the antenna in the magnetic field plane are both within the required envelope, achieving good sidelobe envelope suppression.

[0050] Based on the same design principles as the above-mentioned embodiments, technicians in this field can also design microstrip planar array antennas operating at 22GHz, 24GHz, 30GHz or other frequency bands through routine experiments in accordance with their common technical knowledge and have the same technical effects, which will not be described in detail here.

[0051] Through the description of the above structure and principle, those skilled in the art should understand that the present invention is not limited to the above specific implementations, and improvements and substitutions based on the present invention using the known technology in the art fall within the protection scope of the present invention, and the protection scope of the present invention should be defined by the claims and their equivalents. Parts not described in the specific implementations are prior art or common knowledge.

Claims

1. A millimeter-wave microstrip flat-panel array antenna with low cross-polarization, characterized in that: The millimeter-wave microstrip planar array antenna has an operating frequency band between 22 and 30 GHz; it comprises: a dielectric substrate, a first printed microstrip circuit and a second printed microstrip circuit respectively arranged on the front and back surfaces of the dielectric substrate, and a rectangular metal waveguide fixed to the back surface of the dielectric substrate for feeding; the first printed microstrip circuit is composed of a longitudinal power division circuit, a transverse power division circuit cascaded to the longitudinal power division circuit, and a radiating rectangular patch unit connected to the transverse power division circuit; A coupling microstrip segment for coupling and exciting the radiating rectangular patch unit is provided on the lateral power division circuit. The coupling microstrip segment is spaced apart from the radiating rectangular patch unit and is coupled and excited via a gap. A metallized through hole is provided at the center of the coupling microstrip segment, and the metallized through hole electrically connects the coupling microstrip segment with the second printed microstrip circuit.

2. The low cross-polarization millimeter wave microstrip planar array antenna according to claim 1, characterized in that: The second printed microstrip circuit is a metal floor printed on the back of the dielectric substrate, and a rectangular gap is provided in the center of the metal floor; the rectangular metal waveguide is fixed at the center of the dielectric substrate, and the electromagnetic energy fed from the rectangular metal waveguide is coupled to the first printed microstrip circuit through the rectangular gap.

3. The low cross-polarization millimeter wave microstrip planar array antenna according to claim 2, characterized in that: An input microstrip segment corresponding to the rectangular gap is provided at the center position of the front surface of the dielectric substrate, and two longitudinal power dividing circuits are respectively connected to the upper and lower sides of the input microstrip segment.

4. The low cross-polarization millimeter wave microstrip planar array antenna according to claim 3, characterized in that: A plurality of the transverse power dividing circuits are cascaded outside each of the longitudinal power dividing circuits, and the transverse power dividing circuits and the radiating rectangular patch units are symmetrical along the longitudinal center line and the transverse center line of the dielectric substrate.

5. The low cross-polarization millimeter wave microstrip planar array antenna according to claim 1, characterized in that: The spacing between the horizontal power division circuits at each level is equal.

6. The low cross-polarization millimeter wave microstrip planar array antenna according to claim 1, characterized in that: A plurality of radiating rectangular patches of the same size are connected to each level of the lateral power division circuit, and the spacing between two adjacent radiating rectangular patches is equal.

7. The low cross-polarization millimeter wave microstrip planar array antenna according to claim 1, characterized in that: The conversion section width of the longitudinal power division circuit is designed according to the Taylor amplitude distribution required for sidelobe suppression, and the conversion section width of the transverse power division circuit is the same as that of the longitudinal power division circuit, and the same Taylor amplitude distribution design is used.

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