A multi-resonant cavity coupled fed SIW back cavity broadband wide beam antenna

Abstract

The application discloses a SIW back cavity broadband wide-beam antenna coupled and fed by a multi-resonant cavity, which comprises three layers of dielectric substrates, two layers of semi-cured sheet layers and six layers of metal layers, wherein the first metal layer is provided with a rotating rectangular radiation patch, a coupling L-shaped microstrip structure, a central cross-shaped slot and an edge slot; the middle metal layer is provided with a square cavity metal frame with a local semicircular boundary and an H-shaped coupling slot; and the bottom metal layer is provided with a feeding strip line and a coaxial feeding port. Radio frequency signals are input by the coaxial feeding port, transmitted through the feeding strip line, and coupled to the upper layer radiation structure through the H-shaped slot. The SIW metalized via array forms an equivalent back cavity sidewall, which is used for restraining the cavity mode and improving the radiation pattern stability; the central cross-shaped slot, the edge slot and the parasitic metal loading structure are used for adjusting the surface current distribution of the rotating rectangular radiation patch, and improving the impedance matching, the gain stability, the wide-beam radiation performance and the cross-polarization level.

Description

Technical Field

[0001] This invention relates to the field of millimeter-wave antenna technology, and more particularly to a multi-cavity coupled-fed SIW back cavity wideband beam antenna. Background Technology

[0002] With the development of millimeter-wave radar, wireless communication, and integrated RF front-end technologies, planar antennas operating in the Ka-band are gradually evolving towards miniaturization, high integration, low profile, and high efficiency. Microstrip antennas have advantages such as simple structure, ease of fabrication, and convenient integration with RF circuits. However, traditional microstrip patch antennas are susceptible to dielectric loss, surface waves, feed parasitic effects, and packaging environment in the millimeter-wave band, making it difficult to simultaneously achieve optimal impedance bandwidth, radiation efficiency, and pattern stability.

[0003] SIW structures form equivalent waveguide boundaries within a dielectric substrate through an array of metallized vias, combining the low loss of traditional metal waveguides with the ease of integration of microstrip circuits. By integrating the SIW back cavity with a microstrip radiating patch, a controlled cavity environment can be created within the antenna element, effectively suppressing surface wave propagation and back radiation, thereby improving radiation efficiency and pattern stability.

[0004] Existing multilayer microstrip antennas often employ direct feeding, slot-coupled feeding, or probe feeding to achieve energy transfer. However, in the millimeter-wave band, the size of the feeding structure is sensitive, and manufacturing errors and interlayer alignment deviations can easily lead to impedance matching degradation. At the same time, the ability of a single-layer structure to control the electromagnetic field distribution is limited, making it difficult to achieve wideband matching, stable gain, and low cross-polarization characteristics within a small size.

[0005] Therefore, to address the challenge of simultaneously achieving wideband impedance matching, wide beam coverage, high-efficiency radiation, and miniaturized integration in millimeter-wave microstrip antennas, it is necessary to propose a novel multi-layer coupled-fed microstrip antenna structure. This structure should be able to coordinately control the feed path, cavity boundary, and radiating patch surface current within a limited planar dimension, thereby improving the impedance matching characteristics, radiation efficiency, beam coverage, and pattern stability of millimeter-wave band antennas to meet the application requirements of Ka-band millimeter-wave radar, short-range detection, and miniaturized array antenna elements. Summary of the Invention

[0006] To address the technical challenges of existing millimeter-wave microstrip antennas in simultaneously achieving miniaturization, multi-layer integration, high-efficiency radiation, wideband impedance matching, and wide beam coverage, this invention provides a wideband beam antenna. This antenna achieves energy transfer through a multi-layered metal structure, a SIW back cavity, and a coupled feed path. Furthermore, it utilizes the central cross-shaped slot, edge slots, and parasitic metal loading structures within the first metal layer to adjust the current distribution on the patch surface, forming a frequency-selective coupled radiation structure. This improves impedance matching, gain stability, radiation efficiency, wide beam radiation performance, and polarization purity within the operating frequency band.

[0007] To achieve the above objectives, this invention proposes a multi-cavity coupled-fed SIW back-cavity wideband beam antenna. The antenna comprises, from top to bottom, a first metal layer, a first dielectric layer, a second metal layer, a first prepreg layer, a third metal layer, a second dielectric layer, a fourth metal layer, a second prepreg layer, a fifth metal layer, a third dielectric layer, and a sixth metal layer. The first metal layer has a centrally located rotating rectangular radiating patch, coupled L-shaped microstrip structures distributed around the rotating rectangular radiating patch, and four parasitic metal loading structures disposed around the rotating rectangular radiating patch and maintaining a gap with it.

[0008] The second and fourth metal layers each have a square opening with a partially semi-circular boundary in the middle, with the semi-circular boundary located at the lower left corner of the square opening, and the outer perimeter of the opening being a continuous metal region; the third metal layer has a rotating H-shaped coupling slot at its center; the fifth metal layer has a square opening with a partially semi-circular boundary in the middle, with the semi-circular boundary located at the lower left corner of the square opening, and the outer perimeter of the opening being a continuous metal region; a feed strip is provided within the square opening, and the opening of the fifth metal layer corresponds to the openings of the second and fourth metal layers, and the outer metal region of the fifth metal layer also corresponds to the outer metal region of the second and fourth metal layers, and the feed strip does not contact the outer metal region; a coaxial feed port is provided at the lower left of the sixth metal layer, and the coaxial feed port corresponds to the semi-circular boundary of the fifth metal layer;

[0009] SIW metallized via array is uniformly disposed around the rotating rectangular radiating patch on the L-shaped microstrip structure and penetrates the stacked structure consisting of a multilayer dielectric substrate, a prepreg layer and six metal layers.

[0010] The feed strip in the fifth metal layer is an oblique strip structure. The coaxial feed port in the sixth metal layer is connected to the feed strip. The radio frequency signal is input from the coaxial feed port and coupled to the first metal layer through the feed strip and the H-type coupling gap, which excites the rotating rectangular radiating patch and the parasitic metal loading structure to generate radiation.

[0011] Furthermore, the rectangular radiating patch in the first metal layer is rotated and placed at its center. The coupled L-shaped microstrip structures are distributed around the rotating rectangular radiating patch. The four coupled L-shaped microstrip structures form a square and do not contact each other. The four parasitic metal loading structures are distributed along the four sides of the rotating rectangular patch, which together adjust the near-field coupling strength of the first metal layer and the current distribution at the patch edge.

[0012] Furthermore, the rotating rectangular radiating patch is provided with a cross-shaped slit and an edge groove. The cross-shaped slit is located in the central area of ​​the rotating rectangular radiating patch and is used to divide and adjust the current path on the patch surface. The edge groove is provided at the four apex corners of the rotating rectangular radiating patch, and the four apex corners are spaced apart at the middle of the sides of the square formed by the four coupled L-shaped microstrip structures. It is used to regulate the edge current and equivalent capacitance loading of the patch. Together, they form a frequency-selective radiating patch structure.

[0013] Furthermore, the four parasitic metal loading structures are symmetrically arranged along the rotating rectangular radiating patch and located between the rotating rectangular radiating patch and the coupled L-shaped microstrip structure, forming a gap coupling with the rotating rectangular radiating patch; each parasitic metal loading structure includes metal pads located in the first and second metal layers and metal pillars connecting them, used to introduce tunable parasitic resonance and improve broadband impedance matching.

[0014] Furthermore, the second and fourth metal layers with square openings having local semi-circular boundaries are located above and below the H-shaped coupling slot, respectively, to constrain and adjust the electromagnetic field distribution inside the SIW cavity; the SIW metallized via array serves as an equivalent metal sidewall to suppress surface waves and back radiation and improve the stability of the radiation pattern.

[0015] Furthermore, the H-shaped coupling slot in the third metal layer is composed of three interconnected rectangular slots, located in the middle of the third metal layer, with the middle slot located on the diagonal of the third metal layer. In the stacking direction, the feed strip of the fifth metal layer is perpendicular to the middle slot. The center of the H-shaped coupling slot corresponds to the center of the rectangular radiating patch. The H-shaped coupling slot is used to couple the radio frequency energy in the feed strip to the first metal layer, forming an oblique polarization radiation mode together with the rotating rectangular radiating patch.

[0016] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0017] (1) The first metal layer serves as a radiation control layer, comprising a rotating rectangular radiating patch, a coupled L-shaped microstrip structure, a central cross-shaped slot, an edge groove, and a parasitic metal loading structure. The rotating rectangular radiating patch is located above the SIW back cavity and is used to form the main radiation aperture. The coupled L-shaped microstrip structure is arranged around the rotating rectangular radiating patch and is used to adjust the coupling current distribution near the radiating patch. The central cross-shaped slot and the edge groove are arranged on the rotating rectangular radiating patch and are used to change the local current path and edge current distribution of the patch, thereby adjusting the equivalent impedance and radiation mode within the operating frequency band. The parasitic metal loading structure is symmetrically arranged along the rotating rectangular radiating patch and forms a gap coupling with the rotating rectangular radiating patch to introduce an adjustable parasitic response, further improving the patch edge field distribution, gain stability, wide beam radiation performance, and cross-polarization level.

[0018] (2) Both the second and fourth metal layers have square openings with locally semi-circular boundaries. The opening cavities, together with the SIW metallized via array, are used to adjust the electromagnetic field distribution and resonant mode inside the back cavity, thereby improving the stability of the antenna radiation pattern. The third metal layer has an H-shaped coupling slot, the fifth metal layer has an oblique feed strip, and the sixth metal layer has a coaxial feed port. The radio frequency signal is input through the coaxial feed port of the sixth metal layer, transmitted through the feed strip of the fifth metal layer, and then coupled upwards to the first metal layer radiating structure through the H-shaped slot of the third metal layer. This coupling feeding method can reduce the disturbance of the surface current of the upper radiating patch to direct feeding, which is beneficial to improving impedance matching and polarization stability.

[0019] (3) The SIW metallized via array extends from the first metal layer to the sixth metal layer and forms an equivalent metal sidewall around the radiating patch and cavity region. This sidewall is used to constrain the cavity mode, suppress surface wave diffusion and back radiation, thereby improving the antenna's radiation efficiency and pattern stability. Through the synergistic effect of the rotating rectangular radiating patch, the central cross-shaped slot, the edge slot, the parasitic metal loading structure, the H-type coupling slot, the feed stripline, the square cavity with a semi-circular boundary, and the SIW back cavity, this invention has the advantages of compact structure and easy planar integration. It can achieve wideband impedance matching, stable gain, high-efficiency radiation, low cross-polarization and wide beam coverage near 35GHz in the Ka band. It is suitable for applications such as Ka band millimeter-wave radar, close-range high-resolution detection, millimeter-wave sensing and miniaturized planar array antenna units. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the first-layer radiating structure of the antenna in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the second and fourth layers of the antenna structure according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the H-shaped coupling slot structure of the third layer of the antenna in an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the fifth-layer feed stripline structure of the antenna in an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the sixth layer structure of the antenna in an embodiment of the present invention;

[0025] Figure 6 This is a curve showing the antenna reflection coefficient S11 in an embodiment of the present invention;

[0026] Figure 7 This is a graph showing the maximum gain of the antenna as a function of frequency in an embodiment of the present invention.

[0027] Figure 8 This is a graph showing the overall antenna efficiency as a function of frequency in an embodiment of the present invention.

[0028] Figure 9 This is a diagram showing the main polarization and cross-polarization patterns of the antenna E-plane in an embodiment of the present invention;

[0029] Figure 10 This is a diagram showing the main polarization and cross-polarization patterns of the antenna H-plane in an embodiment of the present invention.

[0030] Figure 11 This is a schematic diagram of the overall three-dimensional structure of the antenna according to an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] In this embodiment, the antenna operates at a center frequency of 35 GHz and is implemented using a multilayer PCB process. The dielectric and prepreg structure from top to bottom is as follows: a first dielectric layer, a first prepreg layer, a second dielectric layer, a second prepreg layer, and a third dielectric layer. The first dielectric layer is made of TLY-5 and has a thickness of 0.762 mm; the second and third dielectric layers are both made of TLY-5 and have a thickness of 0.254 mm; the first and second prepreg layers are both made of fastRise-27 and have a thickness of 0.2 mm.

[0033] like Figure 1As shown, the first metal layer includes four L-shaped coupled microstrip structures, a rotating rectangular radiating patch located in the central region, a central cross-shaped slot and edge groove disposed on the rotating rectangular radiating patch, four non-contact parasitic metal loading structures disposed around the rotating rectangular radiating patch, and an array of metallized vias distributed along the cavity boundary. The arm length of the coupled L-shaped microstrip structure is... It is 1.7mm thick and the arm is wide. The length of the centrally rotated rectangular radiating patch is 0.4 mm. It is 1.8mm wide. The length of the central cross-shaped slit is 1.8mm. It is 1.2mm wide. The length of the edge groove is 0.1mm. It is 0.3mm wide. The spacing between the relatively positioned parasitic metal loading structures is 0.15 mm. The diameter is 1.7mm. The SIW back cavity through-hole extends from the first layer to the sixth layer, and the through-hole diameter is... The spacing between adjacent through holes is 0.3mm. The diameter is 0.6 mm, and an equivalent metal sidewall is formed through this array of through holes.

[0034] like Figure 2 As shown, the second and fourth metal layers have the same structure, both being metal frames with square openings and semi-circular borders. The length of this metal frame... It is 3.4mm wide. It is 3.4mm, and the side length of the central square cavity is... The radius of the semi-circular boundary is 3mm. With a thickness of 0.5mm, this structure is used to adjust the electromagnetic field distribution inside the cavity and together with the upper radiation patch and the lower coupling gap, it forms a multi-layer coupling channel.

[0035] like Figure 3 As shown, an H-shaped coupling slot is provided on the third metal layer. This coupling slot comprises three interconnected rectangular slots, wherein the length of the first coupling slot is... 1mm, width The length of the second coupling gap is 0.2 mm. It is 1.3mm wide. The H-type coupling gap is 0.2mm. It is used to couple the radio frequency energy of the fifth-layer feed stripline to the upper cavity and radiating patch, while reducing the direct disturbance of the feed line to the surface current of the radiating patch.

[0036] like Figure 4 As shown, the fifth metal layer is provided with an obliquely fed strip, and the length of the fed strip is... It is 2.55mm wide. The diameter is 0.5mm. A coaxial power supply port is provided on the sixth metal layer, with a power supply port radius of 0.5mm. The thickness is 0.5mm. The coaxial feed signal is input from the sixth layer, transmitted through the feed stripline of the fifth layer, and coupled upward through the H-shaped gap of the third layer to further excite the rotating rectangular radiating patch of the first layer to generate radiation.

[0037] like Figure 5 As shown, the sixth metal layer is provided with a coaxial feed port, and the radius of the outer conductor of the feed port is... It is 0.5mm.

[0038] The overall antenna structure in this embodiment is as follows: Figure 11 As shown, the antenna employs a multilayer dielectric and metal stacked structure. The first metal layer includes a rotating rectangular radiating patch with a central cross-shaped slot and edge slots, an L-shaped coupled microstrip structure, and a parasitic metal loading structure, which together generate the main radiation. The square cavities of the second and fourth metal layers are used to adjust the cavity mode. The H-shaped coupling slot of the third metal layer is used to achieve electromagnetic energy coupling. The oblique feed stripline of the fifth metal layer and the coaxial feed port of the sixth metal layer are used to input radio frequency signals. Through the synergistic coupling of the above structure in the vertical direction and the planar direction of the first metal layer, comprehensive control of the feed path, coupling strength, cavity boundary, surface current distribution, and radiating aperture can be achieved, thereby improving impedance matching, radiation efficiency, wide beam characteristics, and polarization stability near 35 GHz.

[0039] To verify the beneficial effects of the present invention, electromagnetic simulation was performed on the antenna of the above embodiment, and the results are as follows. Figures 6 to 10 As shown.

[0040] Figure 6 The figure shows the reflection coefficient S11 curve of the antenna in this embodiment. As can be seen from the figure, the antenna maintains good impedance matching characteristics in the range of 30GHz to 39GHz. Except near the low-frequency edge, S11 is basically below -10dB, and about -24dB near 35GHz, indicating that the multi-layer coupled feeding structure of the present invention can effectively achieve Ka-band broadband matching.

[0041] Figure 7 The figure shows the maximum gain of the antenna in this embodiment as a function of frequency. As can be seen from the figure, the antenna achieves a maximum gain of about 5 dBi near 35 GHz, and the gain fluctuates by about 0.2 dB in the range of 30 GHz to 39 GHz, indicating that the antenna has a relatively stable radiation gain over a wide frequency band.

[0042] Figure 8The figure shows the overall antenna efficiency curve for this embodiment. As can be seen from the figure, the overall antenna efficiency remains high in the 30GHz to 39GHz range, reaching approximately 98.5% near 35GHz, and exceeding 95% in most operating frequency bands. This result demonstrates that the SIW cavity back structure and multi-layer coupled feeding method can effectively reduce energy loss.

[0043] Figure 9 and Figure 10 The figures show the main polarization and cross-polarization patterns of the E-plane and H-plane at 35 GHz, respectively. As can be seen from the figures, the antenna's main polarization pattern is stable, the main radiation direction is clear, the cross-polarization component is significantly lower than the main polarization component, and the 3dB beamwidth is around 120°, indicating that the antenna of this invention has a large beamwidth, good polarization purity, and pattern stability.

[0044] In summary, this invention achieves good impedance matching, stable gain, high overall efficiency, and low cross-polarization near 35GHz through the coordinated design of a multi-layer metal structure, SIW back cavity, H-type coupling slot, stripline feeding, and a first-layer center patch, edge slot, and parasitic metal loading structure. It is suitable for applications such as Ka-band millimeter-wave radar, millimeter-wave communication, short-range high-resolution detection, and planar array antenna units.

Claims

1. A multi-cavity coupled-fed SIW back-cavity wideband beam antenna, characterized in that, The antenna includes, from top to bottom, a first metal layer, a first dielectric layer, a second metal layer, a first prepreg layer, a third metal layer, a second dielectric layer, a fourth metal layer, a second prepreg layer, a fifth metal layer, a third dielectric layer, and a sixth metal layer; The first metal layer is provided with a rotating rectangular radiating patch at the center, coupled L-shaped microstrip structures distributed around the rotating rectangular radiating patch, and four parasitic metal loading structures disposed around the rotating rectangular radiating patch and maintaining a gap with it. The second and fourth metal layers each have a square opening with a partially semi-circular boundary in the middle, the semi-circular boundary being located at the lower left corner of the square opening, and the outer perimeter of the opening being a continuous metal region; the third metal layer has a rotating H-shaped coupling slot at its center; the fifth metal layer has a square opening with a partially semi-circular boundary in the middle, the semi-circular boundary being located at the lower left corner of the square opening, and the outer perimeter of the opening being a continuous metal region; a feed strip is provided within the square opening, the opening of the fifth metal layer corresponding to the openings of the second and fourth metal layers, and the outer metal region of the fifth metal layer corresponding to the outer metal regions of the second and fourth metal layers, the feed strip not contacting the outer metal region; a coaxial feed port is provided at the lower left of the sixth metal layer, the coaxial feed port corresponding to the semi-circular boundary of the fifth metal layer; SIW metallized via array is uniformly disposed around the rotating rectangular radiating patch on the L-shaped microstrip structure and penetrates the stacked structure consisting of a multilayer dielectric substrate, a prepreg layer and six metal layers. The feed strip in the fifth metal layer is an oblique strip structure. The coaxial feed port in the sixth metal layer is connected to the feed strip. The radio frequency signal is input from the coaxial feed port and coupled to the first metal layer through the feed strip and the H-type coupling gap, which excites the rotating rectangular radiating patch and the parasitic metal loading structure to generate radiation.

2. The multi-cavity coupled SIW back-cavity wideband beam antenna according to claim 1, characterized in that, The rectangular radiating patch in the first metal layer is rotated and placed at its center. The coupled L-shaped microstrip structures are distributed around the rotating rectangular radiating patch. The four coupled L-shaped microstrip structures form a square and do not contact each other. The four parasitic metal loading structures are distributed along the four sides of the rotating rectangular patch, which together adjust the near-field coupling strength of the first metal layer and the current distribution at the patch edge.

3. The multi-cavity coupled SIW back-cavity wide-bandwidth beam antenna according to claim 2, characterized in that, The rotating rectangular radiating patch is provided with a cross-shaped slit and an edge groove. The cross-shaped slit is located in the central area of ​​the rotating rectangular radiating patch and is used to divide and adjust the current path on the patch surface. The edge groove is provided at the four vertices of the rotating rectangular radiating patch, and the four vertices are spaced apart at the middle of the sides of the square formed by the four coupled L-shaped microstrip structures. It is used to control the edge current and equivalent capacitance loading of the patch. Together, they form a frequency-selective radiating patch structure.

4. The multi-cavity coupled SIW back-cavity wide-bandwidth beam antenna according to claim 1, characterized in that, The four parasitic metal loading structures are symmetrically arranged along the rotating rectangular radiating patch and located between the rotating rectangular radiating patch and the coupled L-shaped microstrip structure, forming a gap coupling with the rotating rectangular radiating patch; each parasitic metal loading structure includes metal pads located in the first and second metal layers and metal pillars connecting them.

5. The multi-cavity coupled SIW back-cavity wide-bandwidth beam antenna according to claim 1, characterized in that, The second and fourth metal layers with square openings with local semi-circular boundaries are located above and below the H-shaped coupling gap, respectively, to constrain and adjust the electromagnetic field distribution inside the SIW cavity; the SIW metallized via array serves as an equivalent metal sidewall.

6. The multi-cavity coupled SIW back-cavity wideband beam antenna according to claim 5, characterized in that, The H-shaped coupling slot in the third metal layer is composed of three interconnected rectangular slots, which are located in the middle of the third metal layer. The middle slot is located on the diagonal of the third metal layer, and the feed strip of the fifth metal layer is perpendicular to the middle slot in the stacking direction. The center of the H-shaped coupling slot corresponds to the center of the rectangular radiating patch. The H-shaped coupling slot is used to couple the radio frequency energy in the feed stripline to the first metal layer, forming a slanted polarization radiation mode together with the rotating rectangular radiating patch.

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