The present application generally relates to a filter for a communication system, and more specifically, to a Suspended Substrate Stripline (SSS) Low Pass Filter (LPF) electrically coupled to a Substrate Integrated Waveguide (SIW) cavity resonator for introducing a notch response.
Radio frequency (RF), microwave, and millimeter wave (mmW) filters may be key components in communication systems such as base stations, large-scale antennas, mobile phones, and the like. The use of mmW for 5G communications may leads to complex filtering challenges; a challenging task above 20 GHz, where filters with high performance characteristics are highly desirable such as: low insertion loss, good transition band, high out of band rejection, and the like.
One well known technology for filters that offers exceptionally low losses and high out of band rejection characteristics is the Suspended Substrate Stripline (SSS) technology. SSS is a Transversal Electromagnetic (TEM) transmission line that may be widely used in microwave and mmW systems. As may be seen in
LPFs and HPFs implemented in SSS technology may have the following characteristics: high Quality factor (Q), low insertion loss, high frequency of operation, high out of band rejection, broadband, good temperature stability, very rugged design, and the like, and can be implemented with distributed elements or in a quasi-lumped approach. The surface mountable approach for the connectorized SSS may be the suspended integrated strip-line (SISL). SSS LPFs and HPFs may be cascaded together to form a very broadband bandpass filter (BPF). A bandstop (notch) characteristic can also be added to the passband response or to the transition band by cascading a SSS LPF filter with a SSS bandstop (notch) filter. An alternative approach for introducing a notch response in the passband is to use a defected stripline structure.
Another filter technology that has gained a lot of interest in recent years for the design of microwave and mmW filters may be the Substrate Integrated Waveguide (SIW). As may be seen in
The integration of a SIW cavity with planar technology, such as Coplanar Waveguide (CPW), Microstrip or Stripline, has led to the realization of different research work in mmW transitions. However, there has been little work that relate to the use of a SIW cavity resonator with a planar transmission line to produce a bandstop (notch) response.
A SSS LPF can be cascade with a SIW cavity notch filter to produce a notch response in the passband or at the transition band, however, a SSS to SIW transition would be required, making the integration of both structures bulky.
Therefore, it would be desirable to provide a system and method that overcomes the above. The system and method would provide a novel integration between a SSS filter LPF and a SIW cavity resonator. The SSS LPF would be electrically coupled to a SIW cavity resonator for introducing a notch response.
In accordance with one embodiment, the integration of a Substrate Integrated Waveguide (SIW) with a Suspended Substrate Stripline (SSS) filter for introducing a notch response is disclosed. The SSS filter has a substrate having metal layers formed on a top surface and a bottom surface thereof. A filter circuit is formed on the top surface of the substrate. A top ground plate is provided and has an air cavity formed on a bottom surface of the top ground plate, wherein the air cavity on the top ground plate is positioned directly above the filter circuit when the top ground plate is positioned on the top surface of the substrate. A bottom ground plate is provided and has an air cavity formed on a top surface of the bottom ground plate, wherein the air cavity on the bottom ground plate is positioned directly below the filter circuit when the bottom ground plate is positioned on the bottom surface of the substrate. A Substrate Integrated Waveguide (SIW) cavity resonator is coupled to the filter circuit to create a notch response in the SSS filter.
In accordance with one embodiment, the integration of a Substrate Integrated Waveguide (SIW) with a Suspended Substrate Stripline (SSS) Low Pass Filter (LPF) for introducing a notch response is disclosed. The SSS LPF has a substrate having metal layers formed on a top surface and a bottom surface thereof. A LPF circuit is formed on the top surface of the substrate. A top ground plate is provided and has an air cavity formed on a bottom surface of the top ground plate, wherein the air cavity on the top ground plate is positioned directly above the LPF circuit when the top ground plate is positioned on the top surface of the substrate. A bottom ground plate is provided and has an air cavity formed on a top surface of the bottom ground plate, wherein the air cavity on the bottom ground plate is positioned directly below the LPF circuit when the bottom ground plate is positioned on the bottom surface of the substrate. A Substrate Integrated Waveguide (SIW) cavity resonator is coupled to the LPF circuit to create a notch response in the SSS LPF. A plurality of vias is formed on the substrate, wherein the plurality of vias comprises: two parallel rows of vias extending through the substrate, wherein the filter is positioned between the parallel rows of vias and a set of vias extending through the substrate delimiting an area of the SIW cavity resonator. An opening is formed in the set of vias delimiting the area of the SIW cavity resonator for coupling the SIW cavity resonator to the LPF circuit.
In accordance with one embodiment, the integration of a Substrate Integrated Waveguide (SIW) with a Suspended Substrate Stripline (SSS)) Low Pass Filter (LPF) for introducing a notch response is disclosed. The SSS LPF has a substrate having metal layers formed on a top surface and a bottom surface thereof. A LPF circuit is formed on the top surface of the substrate. A top ground plate is provided and has an air cavity formed on a bottom surface of the top ground plate, wherein the air cavity on the top ground plate is positioned directly above the LPF circuit when the top ground plate is positioned on the top surface of the substrate. A bottom ground plate is provided and has an air cavity formed on a top surface of the bottom ground plate, wherein the air cavity on the bottom ground plate is positioned directly below the LPF circuit when the bottom ground plate is positioned on the bottom surface of the substrate. A pair of Substrate Integrated Waveguide (SIW) cavity resonators is coupled to the LPF circuit to create a notch response in the SSS LPF. A plurality of vias are formed on the substrate, wherein the plurality of vias comprises: two parallel rows of vias extending through the substrate, wherein the filter is positioned between the parallel rows of vias; a first set of vias extending through the substrate delimiting an area of a first SIW cavity resonator, wherein an opening is formed in the first set of vias delimiting the area of the first SIW cavity resonator for coupling the first SIW cavity resonator to the LPF circuit; and a second set of vias extending through the substrate delimiting an area of a second SIW cavity resonator, wherein an opening is formed in the second set of vias delimiting the area of the second SIW cavity resonator for coupling the second SIW cavity resonator to the LPF circuit.
The present application is further detailed with respect to the following drawings. These figures are not intended to limit the scope of the present application but rather illustrate certain attributes thereof. The same reference numbers will be used throughout the detailed description of the drawings to refer to the same or like parts.
The description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the disclosure and is not intended to represent the only forms in which the present disclosure can be constructed and/or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the disclosure in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and sequences can be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of this disclosure.
Embodiments of the exemplary circuit and method integrate a SIW cavity resonator to a SSS LPF. Depending on the size of the SIW cavity resonator, a notch response can be placed at a passband or at a transition band, thus improving the rejection characteristic with the last option. The coupling between the SIW cavity resonator and the SSS LPF may be controlled by means of a small aperture or iris, separated by vias. The SSS filter and the SIW cavity resonator may be integrated on the same substrate or substrates (when stacking multiple bonding and core layers). Metallic plates may provide the necessary ground and shielding.
Referring to
A filter circuit 315 (hereinafter filter 315) (
In accordance with one embodiment, the filter 315 (
As may be seen in
The SSS LPF 100 (
The device 300 (
Coupling of the SIW cavity resonator 310 to SSS LPF 100 (
In the present embodiment shown, a pair of SIW cavity resonators 310 may be coupled to SSS LPF 100 (
The device 300 (
Each of the vias 304 may be defined to have a diameter d and a pitch p which may be defined as the distance between a center point of adjacent vias 304. For the SIW cavity, the following conditions may be required:
d<(λg/5) (1a)
p≤2d (1b)
0.5<d/p<0.8 (1c)
where λg is the guided wavelength in the SIW.
The conditions 1a-1c are important parameters to minimize leakage loss between vias. Finally, a nonessential but desirable condition for the manufacturing process is to have d comparable to the thickness of the substrate 303. In accordance with one embodiment, the vias 304 may have a diameter of 6 mil and a pitch of 8.8 mil.
The vias 304 may form an enclosed area 310A having an opening 309 to delimit the area of the each of the pair of SIW cavity resonators 310. The enclosed area 310A may be formed by placing vias 304 around a predefined geometric perimeter. As may be shown in
The opening 309 may be used for controlling the coupling between the SIW cavity resonator 310 and the SSS LPF 100 (
In accordance with one embodiment, the integration of a Substrate Integrated Waveguide (SIW) with a Suspended Substrate Stripline (SSS) filter for introducing a notch response is disclosed. The present embodiment may be extended to the Suspended Integrated Strip-Line (SISL).
The foregoing description is illustrative of particular embodiments of the application but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the application.
Number | Name | Date | Kind |
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4521755 | Carlson et al. | Jun 1985 | A |
5319329 | Shiau et al. | Jun 1994 | A |
20210337638 | Kunkee et al. | Oct 2021 | A1 |
Number | Date | Country | |
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20230352805 A1 | Nov 2023 | US |