Ka-band broadband filtering antenna

Abstract

The invention discloses a Ka-band broadband filtering antenna, which comprises a probe, a ground paving layer, and a first horizontal dielectric plate, a first radiation patch, a second horizontal dielectric plate and a second radiation patch which are arranged on the ground paving layer, and is characterized in that the first radiation patch is provided with a c-shaped groove, the c-shaped groove is internally provided with a circular groove, and the circular groove is internally provided with a pair of branches; one ends of the two branches are combined to form a combined end connected to the first radiation patch, and the other ends of the two branches are parallel and have a gap to form a parallel opening end; and the center of the second radiation patch is close to the combined end of the two branches on the first radiation patch and far away from the parallel opening ends of the two branches on the first radiation patch. According to the invention, through collaborative design of slotting and branch knot loading, a filtering structure is innovatively constructed. The core innovation lies in the collaborative design of the two filtering structures and the spread spectrum structure, and the filtering frequency domain and the passband width are remarkably improved. The method can be widely applied to the fields of base stations, national defense and military industry and the like.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and specifically relates to a Ka-band filter antenna. Background Technology

[0002] To avoid interference from devices operating on adjacent frequency bands, antennas and filters are typically cascaded, but this method consumes a significant amount of space. In recent years, the industry has introduced the concept of filtered antennas. This involves integrating a filter structure into a traditional antenna design, enabling it to perform both radiation and filtering functions simultaneously. This saves on filter costs and system space, achieving miniaturization of the entire system, while also avoiding losses and significantly reducing mutual interference between antennas operating at different frequencies.

[0003] There are three main design methods for filter antennas. The first method is direct cascading, where the ends of filters with the same impedance are cascaded to the antenna input port. The bandpass, high-pass, low-pass, and band-stop responses of the filters are then substituted into the antenna's radiation response. This avoids impedance mismatch and reduces energy loss. However, this design requires separate design of the two components, and sometimes a separate matching circuit, which not only increases losses but also inevitably increases size and weight.

[0004] The second design method is the equivalent substitution method, which, as the name suggests, replaces the last stage resonator of the filter with an antenna. This increases the designer's flexibility in designing the filter antenna and also reduces its size to some extent. However, the filter's order affects selectivity, and it cannot eliminate the filter's inherent insertion loss.

[0005] The third approach is a fusion design. Without introducing a filter circuit, it generates radiation nulls at low and high frequencies by adding parasitic patches, electromagnetic coupling, stacking techniques, and open / short stubs, achieving in-band radiation and out-of-band filtering characteristics. This approach is characterized by miniaturization, integration, and multifunctionality. This invention chooses a fusion design.

[0006] High-throughput communication satellites (HTS) typically allocate the 27.7-29.5GHz / 17.7-19.7GHz frequency bands to gateway stations. Designing a filter antenna with a passband of 27-31GHz and a stopband of 17.7-21GHz in this frequency band is significant for future satellite network communication.

[0007] With its advantages of small size, high suppression level within the stopband and high bandwidth, integrated broadband filter antennas have become one of the cutting-edge research directions for communication satellites. Summary of the Invention

[0008] To address the problem of how to make an antenna have both broadband characteristics and a high level of stopband suppression in the frequency domain, a Ka-band broadband filter antenna is provided, which enables the antenna to have both broadband characteristics and a good level of stopband suppression.

[0009] This invention innovatively integrates two filtering structures into a single patch antenna, achieving out-of-band suppression over a wide frequency range without increasing the antenna area. This effectively solves the problems of narrow suppression bandwidth and large area associated with traditional filtering antennas. By stacking patch antennas and carefully selecting the dielectric thickness and patch placement, the spread-spectrum structure and the filtering structure can coexist, expanding the frequency range. This invention offers high integration and a small footprint, providing a novel solution for satellite communications.

[0010] To implement this solution, the following structure is adopted: A filter antenna includes: a probe, a ground plane, and a first horizontal dielectric substrate, a first radiating patch, a second horizontal dielectric substrate, and a second radiating patch disposed on the ground plane, characterized in that the first radiating patch has a C-shaped groove, a circular groove is disposed within the C-shaped groove, and a pair of branches are disposed inside the circular groove; One end of the two branches merges to form a merged end that connects to the first radiating patch, and the other ends of the two branches are parallel and have a gap to form a parallel open end. The center of the second radiating patch is located near the merging end of the two branches on the first radiating patch and away from the parallel opening end of the two branches on the first radiating patch. The signal first enters the probe, is transmitted through the probe to the first radiating patch, and the first radiating patch couples the signal to the second radiating patch, from which it radiates outward.

[0011] The antenna's two resonances are contributed by the driving patch and the stacked patch, respectively. This theory also applies to the proposed antenna, where the higher resonant frequency is determined by the stacked patch, while the lower resonant frequency is determined by the driven patch.

[0012] The C-shaped slot, 4.8 mm long, is close to half a wavelength at 18 GHz, generating destructive radiation in the far field, effectively canceling out radiation and resulting in a zero radiation point in that direction. This is crucial for ensuring that access points in transmission mode do not interfere with unrelated sites. The center of the C-shaped slot coincides with the center of the circular slot. This ensures that even with the slotted interior, the internal current remains uniformly distributed at 18 GHz, effectively canceling out the external current. The stubs within the slot, each 4.3 mm long, are close to half a wavelength at 20 GHz. The multiple bends in each stub and the symmetrical placement of two stubs contribute to destructive radiation in the far field.

[0013] The first radiating patch is square. The second radiating patch is rectangular. The rectangular second radiating patch avoids the C-shaped groove and stub positions of the square patch, thus preventing interference with out-of-band suppression capability. It also covers the radiation-generating area of ​​the first radiating patch at 28 GHz, allowing the radiation to be effectively conducted to the second radiating patch, exciting a corresponding field on the second radiating patch, which is then radiated outwards.

[0014] The probe first passes vertically through the ground plane, then vertically through the first horizontal dielectric substrate and connects to the first radiating patch on the first horizontal dielectric substrate, serving as a feeding structure. This probe-type feeding method has advantages in antenna size compared to microstrip line side feeding and causes less interference to the second radiating patch. Compared to slot-coupled feeding, it is structurally simpler and directly connected to the patch, offering higher reliability.

[0015] The connection point of the probe on the first radiating patch is located at the opening of the C-slot of the first radiating patch. This position can conduct the signal into the C-slot or stub at 17.7-21 GHz, producing out-of-band suppression, and can also conduct the signal to the main radiation area of ​​the first radiating patch at 27-31 GHz. Therefore, impedance matching is relatively good at this position.

[0016] The first horizontal dielectric plate, the first radiating patch, the second horizontal dielectric plate, and the second radiating patch are sequentially stacked on the ground layer.

[0017] Specifically, a filtered antenna includes a first horizontal dielectric substrate, a second horizontal dielectric substrate, a ground plane, a first radiating patch, a second radiating patch, and a probe. The probe is perpendicular to the horizontal plane and extends from the ground plane to the upper side of the first horizontal dielectric substrate, serving as a feeding structure. The first radiating patch is located on the upper side of the first horizontal dielectric substrate, and the second radiating patch is located on the upper side of the second horizontal dielectric substrate.

[0018] The first radiating patch has a C-shaped slit and a circular slit inside the C-shaped slit. Inside the circular slit is a pair of symmetrical branches, one side of which is connected to the patch, and the other side is not connected to the patch. The second radiating patch is located above and to the right of the center of the first radiating patch.

[0019] In use, the signal is input by the probe, coupled to the second radiation patch through the first radiation patch, and then radiated outward from the second radiation patch.

[0020] Furthermore, the center of the C-shaped slit coincides with the center of the circular slit. Furthermore, the first radiating patch is square, and the second radiating patch is rectangular.

[0021] Furthermore, the center of the first radiating patch is to the left of the center of the second radiating patch.

[0022] Furthermore, all the horizontal media plates are made of RA300 board material.

[0023] In this invention, at a corresponding frequency of the C-shaped groove of the first radiating patch, currents in opposite directions are generated on the upper and lower sides of the groove. At another frequency, the double-stub current mode is opposite to the adjacent current and does not radiate outward, thus forming two radiation zeros, thereby possessing filtering capability. The coupling effect between the first and second radiating patches forms two radiation frequency domains. When the two radiation frequency domains are close together, a broadband radiation frequency domain is formed.

[0024] Compared with the prior art, the present invention has the following advantages: This invention achieves a good stopband suppression level for the antenna by using two radiation nulls, and all filtering structures are located inside the antenna without increasing the area. The stopband range is 17.7-21 GHz, which can effectively filter interference from another frequency band of high-throughput communication satellites.

[0025] The filter antenna proposed in this invention uses a stacked structure to form two resonant points within the passband, thereby extending the bandwidth. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the front structure of this embodiment.

[0027] Figure 2 This is a top view of the structure of the first radiating patch in this embodiment.

[0028] Figure 3 This is a top view of the second radiating patch in this embodiment.

[0029] Figure 4 This is a graph showing the reflection coefficients of the second radiating patch at different widths.

[0030] Figure 5 The diagram shows the reflection coefficient at different feed locations.

[0031] Figure 6 This is a reflection coefficient diagram at different locations of the second radiating patch.

[0032] Figure 7 This is a graph showing the reflection coefficients of the first reflective patch at different lengths.

[0033] Figure 8 This is a graph showing the reflection coefficients of the first reflective patch at different widths.

[0034] Figure 9 This is a diagram showing the reflection coefficients of media with different thicknesses.

[0035] Figure 10 This is the radiation pattern of this embodiment.

[0036] Figure 11 This is a surface current diagram of the first radiating patch in this embodiment at 18 GHz.

[0037] Figure 12 This is a surface current diagram of the first radiating patch in this embodiment at 20 GHz.

[0038] Figure 13 This is a front view of the array antenna configured in this embodiment.

[0039] Figure 14 This is a top view of the array antenna configured in this embodiment.

[0040] Figure 15 This is a diagram showing the reflection coefficients of each antenna in the array antenna.

[0041] Figure 16 This is the e-plane radiation pattern of the array antenna composed of this embodiment.

[0042] Figure 17 This is a gain diagram for this embodiment.

[0043] Figure 18 This is a reflection coefficient diagram for this embodiment. Detailed Implementation

[0044] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0045] The fusion-filtered broadband antenna of the present invention mainly operates in the K and Ka bands, with the K band operating at 17.7-21 GHz and providing out-of-band suppression, and the Ka band operating at 27-31 GHz and radiating linearly polarized waves.

[0046] like Figure 1 As shown, a fused filtering broadband antenna is provided. The antenna structure, from top to bottom, includes: a first horizontal dielectric substrate, a first radiating patch, a second horizontal dielectric substrate, and a second radiating patch.

[0047] Both the first and second horizontal dielectric substrates are made of RA300 material and have a thickness of 0.5mm. Figure 9The reflection coefficient curves of different dielectric thicknesses are shown in the figure. It can be seen that when the thickness decreases, the bandwidth of the first and second radiating patches becomes 27.7 GHz - 29.5 GHz. When the thickness increases, the bandwidth becomes 29 GHz - 32.3 GHz, which does not meet the bandwidth requirements. This is because the change in dielectric thickness leads to changes in the coupling between the first and second radiating patches. Too thin a dielectric results in excessively strong coupling, while too thick a dielectric results in excessively weak coupling. The antenna cannot achieve impedance matching balance at the two resonant points; therefore, neither too thick nor too thin a dielectric can form a wide passband.

[0048] like Figure 2 As shown, in this embodiment, the first radiating patch is 2.4 mm long and 2.4 mm wide. A C-shaped groove 1 is located on the left side of the patch's center. The length of the C-shaped groove notch is greater than the diameter of the probe 2 to accommodate the probe. A pair of stubs 4 are placed in a circular groove 3, with their ends connected and their tails parallel. To make the stub length as close as possible to half the wavelength of 20 GHz, an arc-shaped structure is used in the middle. The total length of the C-shaped groove is 4.8 mm, and the stub length is 4.3 mm. To allow the C-shaped groove to accommodate the stubs, the width of the C-shaped groove is 0.1 mm.

[0049] like Figure 7 As shown, the length of the first radiating patch affects the low resonant frequency of the passband. When the patch becomes longer, the low resonant frequency of the passband shifts to a lower frequency, and when the patch becomes shorter, the frequency shifts to a higher frequency.

[0050] like Figure 8 As shown, the width of the first radiating patch affects the passband impedance matching and passband range. When the radiating patch is narrower, the impedance matching is better, but the passband range is narrower. When the radiating patch is wider, the impedance matching deteriorates significantly, the reflection coefficient is greater than -10dB, and the antenna cannot effectively radiate signals.

[0051] The second radiating patch is located on the upper side of the second parallel dielectric plate, with its center 0.5 mm to the right of the first patch. Figure 6 The figure shows the antenna reflection coefficient when the second radiating patch is located at different positions. As can be seen from the figure, when the center of the second radiating patch is closer to the center of the first radiating patch, the impedance matching of the first resonant point in the passband is good, but the impedance matching of the second resonant point deteriorates significantly, resulting in only one low-frequency resonant point in the passband. When the center of the second radiating patch is farther from the center of the first radiating patch, the impedance matching of the second resonant point in the passband is good, but the impedance matching of the first resonant point deteriorates significantly, resulting in only one high-frequency resonant point in the passband.

[0052] The second radiating patch is 3mm long and 2mm wide.

[0053] The width of the second radiating patch affects impedance matching. For example... Figure 4As shown, when the width is not 2mm, the passband is narrow or even non-existent.

[0054] Probe 2 is inserted from the bottom to one side of the C-shaped slot opening, 0.75mm away from the center of the first patch antenna, and does not extend to the second patch.

[0055] Figure 18 This is the reflection coefficient curve of the antenna of the present invention. It can be seen that the reflection coefficient is below -10dB in the 27-31GHz passband range, indicating good impedance matching and verifying the broadband characteristics described above.

[0056] Figure 17 This is the radiation gain curve of the antenna of the present invention. It can be seen that in the 17.7-21 GHz range, the radiation gain is within -10 dB, and the curve has two distinct troughs, corresponding to the out-of-band suppression of the C-slot and the out-of-band suppression of the stub, respectively, as described above. In the passband range of 27-31 GHz, the gain is 5 dB, and the in-band gain is flat.

[0057] Figure 10 The image shows the e-plane radiation pattern at a typical frequency of 30 GHz. It can be seen that the half-power beamwidth is 25°. This narrow half-power beamwidth effectively prevents signals from propagating to other areas, avoiding signal interception and encryption, thus effectively ensuring communication security.

[0058] Figure 13 An antenna array using the filtered antenna of this invention as a unit is given. Sixteen antennas are arranged in a 2*8 pattern with a spacing of 5.5 mm. Figure 16 This is the far-field radiation pattern of the array, which shows that the array gain is 16.9 dB. Figure 15 The diagram shows the reflection coefficients of each antenna in the array. From the impedance matching of each antenna element in the array, the difference between s11 after the array is formed and s11 before the array is formed is within 5dB. This indicates that after the array is formed, the antenna elements are not greatly affected by the surrounding antenna elements, showing good array decoupling characteristics.

[0059] This embodiment ensures that the antenna does not occupy additional space when achieving filtering performance. The disclosed antenna has a wide bandwidth, flat passband gain, strong out-of-band harmonic suppression capability, and stable radiation pattern, so that this embodiment can be applied to the field of wireless communication with complex spectrum. The wireless communication includes, but is not limited to, base station communication, satellite communication, and wireless local area network. Furthermore, the antenna can be extended into linear array, area array, and other forms of array.

Claims

1. A Ka-band broadband filtering antenna comprising a probe, a ground plane and a first horizontal dielectric plate, a first radiating patch, a second horizontal dielectric plate, a second radiating patch disposed on the ground plane, characterized in that, The first radiation patch is provided with a c-shaped slot, a circular slot is arranged in the c-shaped slot, and a pair of branches are arranged in the circular slot; One end of the two branches is combined to form a combined end connected to the first radiation patch, and the other end of the two branches is parallel and has a gap to form a parallel open end; The center of the second radiation patch is located close to the combined end of the two branches on the first radiation patch and away from the parallel open end of the two branches on the first radiation patch; The signal first enters the probe, is transmitted to the first radiation patch through the probe, the first radiation patch couples the signal to the second radiation patch, and the second radiation patch radiates outward.

2. The Ka-band wideband filtering antenna according to claim 1, characterized in that, The center of the c-shaped slot coincides with the center of the circular slot.

3. The Ka-band wideband filtering antenna according to claim 1, wherein, The first radiation patch is square.

4. The Ka-band wideband filtering antenna according to claim 1, wherein, The second radiation patch is rectangular.

5. The Ka-band wideband filtering antenna according to claim 1, wherein, The probe first vertically penetrates the ground layer, then vertically penetrates the first horizontal medium plate, and is connected with the first radiation patch on the first horizontal medium plate as a feeding structure.

6. The Ka-band wideband filtering antenna according to claim 5, wherein, The connection point of the probe on the first radiation patch is located at the opening of the c-shaped slot of the first radiation patch.

7. The Ka-band wideband filtering antenna according to claim 1, wherein, The first horizontal medium plate, the first radiation patch, the second horizontal medium plate, and the second radiation patch are sequentially stacked on the ground layer.

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