Low-profile dual-polarization filtering phased-array antenna based on micro-mode SIW resonant cavity

Abstract

The invention discloses a low-profile dual-polarization filtering phased-array antenna based on a micro-mode SIW resonant cavity, and belongs to the technical field of antenna engineering. According to the invention, a micro-mode SIW resonant cavity is provided, and then two pairs of miniaturized micro-mode SIW filtering structures based on the micro-mode SIW resonant cavity are introduced into a feed structure of a microstrip patch antenna, so that a miniaturized dual-polarization filtering antenna unit is formed. The bandwidth is regulated and controlled by regulating and controlling the interdigital coupling groove between the two micro-mode SIW resonant cavities, the impedance matching is regulated through the U-shaped micro-strip transition structure, and the current balance and the electromagnetic shielding between the micro-strip patch antenna and the micro-mode SIW resonant cavities are respectively ensured by forming the arc-shaped groove and the open circuit column in the micro-strip patch antenna. The size of the finally optimized antenna unit is only 27mm * 27mm * 2.5 mm (0.45 lambda c * 0.45 lambda c * 0.04 lambda c, wherein lambda c is the central frequency wavelength of the free space). Simulation shows that the provided filtering phased-array antenna can guarantee 0-45-degree stable beam scanning in a 4.5-5.5 GHz passband, and suppression larger than 25 dB is achieved in a stop band.

Description

Technical Field

[0001] This invention belongs to the field of antenna engineering technology, specifically relating to a filtered phased array antenna based on a micro-mode SIW (Substrate Integrated Waveguide) resonant cavity, which features low profile, simple structure, and high compactness. Background Technology

[0002] In recent years, filtered antennas have received extensive research and discussion due to their advantage of combining filtering and radiation functions. However, the constraints of antenna element size and spacing in phased arrays make it challenging to implement dual-polarized antenna elements with filtering capabilities, especially considering the large-scale integration of multi-channel RF chips. Therefore, designing a simple, compact, low-profile filtered phased array antenna with dual-polarization scanning capability is of great significance. Integrating filtering functionality into phased array antenna elements typically relies on multi-layer designs. For example, the paper "Wideband dual-polarized planar phased array using filtennaelements for vehicular satellite communications" employs stacked patch antennas and microstrip structures, using a 7-layer PCB to achieve dual-polarization scanning and filtering functions in a phased array antenna. In the paper "SIWcavity-fed filtennas for 5G millimeter-wave applications," a multi-layer resonance was implemented on a four-layer PCB structure, using a fully shielded one-eighth-mode SIW resonant cavity and stacked patch antennas to introduce in-band filtering response, thus realizing a dual-polarized filtered phased array antenna. However, the designs in the above articles still rely too heavily on multi-layer designs. Summary of the Invention

[0003] Building upon the prior art, this invention proposes a low-profile dual-polarization filtered phased array antenna based on a micro-mode SIW resonant cavity. The antenna element comprises a miniaturized micro-mode SIW second-order filter structure, a microstrip patch antenna, and an L-shaped feed structure connecting the two. It can simultaneously achieve radiation and filtering functions, maintaining stable performance even when scanning to 45°. The overall structure employs a double-layer PCB design, simplifying fabrication, resulting in a low profile and high compactness, making it more suitable for various applications.

[0004] The technical solution adopted in this invention is as follows: A low-profile dual-polarized filter phased array antenna based on a micro-mode SIW resonant cavity is disclosed. The antenna consists of an array of antenna elements, each of which is a square planar structure. From bottom to top, the elements are: a ground plane, a first dielectric substrate, a second-order micro-mode SIW filter structure layer, a second dielectric substrate, and a dual-polarized fed patch antenna layer. The second-order micro-mode SIW filter structure and the dual-polarized fed patch antenna are connected through a feeding structure. The micro-mode SIW second-order filtering structure includes two sets of filtering modules. Each set of filtering modules includes: two right-angled triangular micro-mode SIW resonant cavities with a wedge angle of 15° and a pair of microstrip feed lines; one resonant cavity is connected to one microstrip line; the two SIW resonant cavities with a wedge angle of 15° are closely placed together in a mirror image manner along the hypotenuse, and the adjacent sides are connected by opening a cross-toe coupling slot to regulate the electrical coupling between them, thereby achieving the effect of regulating the passband bandwidth; the right-angled side of the SIW resonant cavity with an angle of 15° with the hypotenuse has a sawtooth groove structure to extend the current path; one end of each of the two microstrip feed lines is connected to the 15° wedge angle portion of the two SIW resonant cavities respectively, the other end of one microstrip line is connected to a coaxial feed probe, and the other end of the other microstrip line is connected to a dual-polarized fed patch antenna layer through a probe; The dual-polarized fed patch antenna layer is a square metal patch. The connection part with the micro-mode SIW second-order filter structure is a microstrip line extending outward from the square metal patch. This microstrip line module is connected to the micro-mode SIW second-order filter structure through a probe. The square metal patch of the dual-polarized fed patch antenna layer is located at the lower right corner of the square antenna element. The micro-mode SIW resonant cavities of the two filter modules are arranged opposite each other, located on the left and top of the square antenna element, respectively. The projections of the two filter modules and the square metal patch of the dual-polarized fed patch antenna layer do not coincide.

[0005] Furthermore, in the micro-mode SIW second-order filter structure, the microstrip feed line connected to the dual-polarized feed patch antenna layer is U-shaped, and the microstrip feed line connected to the coaxial feed probe is L-shaped.

[0006] Furthermore, in the right-angled triangular micro-mode SIW resonant cavity with a wedge angle of 15° and an angle of 75° with the hypotenuse, multiple circular holes are formed on the right-angled side.

[0007] Furthermore, a ring of metallized through holes is formed around the coaxial feed probe.

[0008] Furthermore, the square metal patch of the dual-polarized fed patch antenna layer has slotted corners, separating four isosceles right-angled triangles. An open-circuit metal post is driven downwards from the right-angle vertex of each isosceles right-angled triangle, serving as an open-circuit stub. This helps reduce electromagnetic interference between the patch antenna and the filtering structure, improving filtering performance. There is one patch antenna within each antenna element, fed by the two sets of feeding structures below. Simultaneously, the microstrip patch antenna can also be considered the final stage of the second-order filtering structure below, forming a third-order filtering structure overall, ultimately manifesting as a dual-polarized third-order filtering antenna.

[0009] The antenna of this invention uses a patch antenna as the radiating element, which has low profile characteristics; it uses a miniaturized second-order micro-mode SIW resonant cavity to obtain the filtering response, resulting in a compact structure; two sets of second-order micro-mode SIW filter structures are placed inside one antenna element, and the filter structure and patch antenna are connected by a simple L-shaped probe to achieve dual polarization function; the filter structure and antenna structure are completely integrated inside one antenna element and arranged in an array, which has dual polarization scanning capability; the overall structure is based on a two-layer PCB structure, which is easy to manufacture and has low cost. Attached Figure Description

[0010] Figure 1 This is a 3D view of the antenna unit.

[0011] Figure 2 This is a top view of the lower micro-module SIW structure.

[0012] Figure 3 This is a top view of the upper microstrip patch antenna.

[0013] Figure 4 The diagram shows three resonant structures and their corresponding coupling topologies.

[0014] Figure 5 The graph shows the gain curve and emission coefficient results for the antenna element.

[0015] Figure 6 This is an isolation diagram for the two polarization ports.

[0016] Figure 7 The diagram shows the coupling coefficients between the two micro-mode SIW resonant cavities.

[0017] Figure 8 This is a graph showing how the bandwidth of the antenna element varies with the length of the interdigitated coupling slot.

[0018] Figure 9 The image shows the beam scanning of an 8×8 phased array antenna in the E-plane and H-plane, respectively. Detailed Implementation

[0019] The passband of the filtered phased array antenna in this embodiment is 4.5-5.5 GHz. Its 3D antenna structure view and detailed diagrams of each layer are shown below. Figure 1-3 The antenna element size is 27mm*27mm*2.5mm (0.45λ). c *0.45λ c *0.04λ c , where λ c (This refers to the center frequency wavelength in free space). This antenna unit comprises a metal ground plane 1, a dielectric substrate 2, and a dielectric substrate 3. The microstrip patch antenna on the upper layer and the two micro-mode SIW filter structures on the lower layer are combined to achieve dual-polarized radiation and third-order filtering effects.

[0020] In this embodiment, the dielectric substrate 2 is F4BM-350, with a thickness of 0.5 mm and a relative permittivity of 3.5. Figure 2 As shown, two micro-mode SIW filter structures 4 are printed on a dielectric substrate 2. Each micro-mode SIW filter structure includes a pair of SIW coupled resonant cavities 5 and a pair of microstrip impedance transformation lines 6. Each resonant cavity 5 contains two micro-mode resonant cavities, with interdigitated coupling slots approximately 4.2 mm long and 0.2 mm wide on adjacent sides. Six metal vias are drilled at the short right-angled sides of the resonant cavities to connect to a metal ground plane, forming an electric wall. A serrated groove with a width of 0.2 mm is formed on the long right-angled sides of the resonant cavities to extend the current path. The wedge-shaped portions of the two micro-mode SIW resonant cavities are connected to fine strip lines with a width of 0.3 mm, gradually transitioning to 1.5 mm. The two microstrip lines are connected to the coaxial feed core and the L-shaped probe, respectively. The microstrip line connected to the L-shaped probe is bent into a U-shape to improve impedance matching, making full use of space. Each micro-mode SIW filter structure occupies an area of ​​18.6 * 6.4 mm, accounting for 0.16 of the entire antenna element aperture area.

[0021] In this embodiment, the dielectric substrate 3 is F4BM-220, with a thickness of 2mm and a relative permittivity of 2.2. Figure 3As shown, a square microstrip patch antenna 7, measuring 19.3mm x 19.3mm, is printed on the dielectric substrate 3. Structure 8 is a metal pillar connected to 7 at the top via a short metal wire and to a microstrip branch of the micromode SIW filter structure at the bottom, enabling side feeding of the microstrip patch antenna. Structure 9 is the coaxial feed core, surrounded by a ring of shielding metal pillars (structure 10) to shield the feed point from interference between the feed point and the patch antenna. An arc-shaped groove is cut into the patch antenna near the feed point to provide space for the shielding metal pillar. To ensure current balance on the patch antenna, the number of arc-shaped grooves above the patch antenna is extended to eight, symmetrically distributed. Structure 11 consists of open metal pillars distributed at the four corners of structure 7, with slotted corners. These open metal pillars penetrate the dielectric substrate 3 downwards but are not connected to the ground plane, serving as a shielding structure between the microstrip patch antenna and the micromode SIW resonant cavity.

[0022] In this embodiment, the three resonant structures that produce the third-order filtering effect and their corresponding coupling topology are as follows: Figure 4 As shown, for one polarization, the third-order filter structure consists of three resonant cavities: two micro-mode SIW resonant cavities 12 and 13, and a microstrip patch 14. The first-order micro-mode SIW resonant cavity 12 is connected to the coaxial feed core via a microstrip line, and the two micro-mode SIW resonant cavities are electrically coupled through an interdigital coupling slot. The third-order microstrip patch antenna 14 is connected to the second-order micro-mode SIW resonant cavity 13 via a metal pillar.

[0023] The filtering response results of the third-order filter structure are given in the example, such as Figure 5 As shown, the reflection coefficient curve exhibits three resonant points within the 4.5-5.5 GHz range, with the in-band emission coefficient approximately less than -10 dB. The peak gain curve shows that the passband gain closely matches the ideal gain trend, with a loss of less than 2 dB. The low-frequency stopband rejection ratio is greater than 30 dB, and the high-frequency stopband rejection ratio is greater than 25 dB. This achieves both stable radiation in the passband and efficient stopband suppression, demonstrating significant application potential.

[0024] The isolation results between the two polarizations are given in the examples, such as Figure 6 As shown, the isolation between the two polarizations is greater than 20 dB in the passband and greater than 30 dB in the stopband.

[0025] The embodiment provides results showing the coupling coefficient between the two micromode SIW resonant cavities as a function of the length of the interdigitated coupling slot, such as... Figure 7 As shown, it can be seen that with the increase of the coupling groove length, the coupling coefficient between the micro-mode SIW resonant cavities gradually increases, and the two are positively correlated.

[0026] The embodiment provides results showing the bandwidth of the antenna element as a function of the lengths of the two interdigitated coupling slots, such as... Figure 8 As shown, the antenna's passband bandwidth gradually expands towards lower frequencies as the length of the coupling slot increases. When the length of the toe coupling slot exceeds 4.2 mm, the reflection coefficient and gain within the passband deteriorate. A passband performance of 4.2 mm achieves the best compromise.

[0027] The embodiment shows the beam scanning of an 8×8 phased array antenna in the E-plane and H-plane, respectively. Figure 9 As shown, at 5 GHz, the main beam remains stable during scanning from 0 to 45°, while the gain drops by about 2 dB during scanning at 45°.

Claims

1. A low-profile dual-polarized filter phased array antenna based on a micro-mode SIW resonant cavity, the antenna being composed of an array of antenna elements, each antenna element being a square planar structure, comprising, from bottom to top: a ground plane, a first dielectric substrate, a micro-mode SIW second-order filter structure layer, a second dielectric substrate, and a dual-polarized fed patch antenna layer; the micro-mode SIW second-order filter structure and the dual-polarized fed patch antenna are connected through a feeding structure; The micro-mode SIW second-order filtering structure includes two sets of filtering modules, each set of filtering modules including: The system consists of two right-angled triangular micro-mode SIW resonators with a wedge angle of 15° and a pair of microstrip feed lines; each resonator is connected to a microstrip line; the two SIW resonators with a wedge angle of 15° are placed close together in a mirror image along their hypotenuses, and the adjacent sides are connected by interdigital coupling slots to regulate the electrical coupling between them, thereby controlling the passband bandwidth; the right-angled sides of the SIW resonators with a 15° angle to the hypotenuses have sawtooth groove structures to extend the current path; one end of each of the two microstrip feed lines is connected to the 15° wedge angle portion of the two SIW resonators, the other end of one microstrip line is connected to a coaxial feed probe, and the other end of the other microstrip line is connected to a dual-polarized feed patch antenna layer through a probe; The dual-polarized fed patch antenna layer is a square metal patch. The connection part with the micro-mode SIW second-order filter structure is a microstrip line extending outward from the square metal patch. This microstrip line module is connected to the micro-mode SIW second-order filter structure through a probe. The square metal patch of the dual-polarized fed patch antenna layer is located at the lower right corner of the square antenna element. The micro-mode SIW resonant cavities of the two filter modules are arranged opposite each other, located on the left and top of the square antenna element, respectively. The projections of the two filter modules and the square metal patch of the dual-polarized fed patch antenna layer do not coincide.

2. The low-profile dual-polarization filtered phased array antenna based on a micro-mode SIW resonant cavity as described in claim 1, characterized in that, In the micro-mode SIW second-order filter structure, the microstrip feed line connected to the dual-polarized feed patch antenna layer is U-shaped, and the microstrip feed line connected to the coaxial feed probe is L-shaped.

3. The low-profile dual-polarization filtered phased array antenna based on a micro-mode SIW resonant cavity as described in claim 1, characterized in that, In the second-order filter structure of the micro-mode SIW, multiple circular holes are opened on the right-angled side of the right-angled triangle micro-mode SIW resonant cavity with a wedge angle of 15° and an angle of 75° with the hypotenuse.

4. The low-profile dual-polarization filtered phased array antenna based on a micro-mode SIW resonant cavity as described in claim 1, characterized in that, A ring of metallized through holes is formed around the coaxial feed probe.

5. The low-profile dual-polarization filtered phased array antenna based on a micro-mode SIW resonant cavity as described in claim 1, characterized in that, The square metal patch of the dual-polarized fed patch antenna layer has slots at its four corners, separating four isosceles right triangles. At the right-angle vertex of each isosceles right triangle, an open-circuit metal post is driven downward as an open-circuit branch.

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