Patent Application
20160301123
This invention relates generally to microwave cavity filters, and more particularly to a dual mode dielectric resonator loaded cavity filter.
The assignee of the present invention manufactures and deploys spacecraft for, inter alia, communications and broadcast services from geosynchronous orbit. A substantial number of radio frequency (RF) filters are required in such spacecraft. For example, a satellite input multiplexor (IMUX) may utilize a number of microwave channel filters, each filter having the functionality of separating and isolating a specific respective signal or bandwidth frequency from a broadband uplink signal received by a spacecraft antenna.
IMUX channel filters are required to exhibit high selectivity and high Q. These filters may include a plurality of cylindrical cavities, each cavity including an internally disposed disk-like dielectric resonator (or “puck”) to improve filter Q relative to physical size and bandwidth. Such filters are described, for example in U.S. Pat. Nos. 6,297,715, 8,907,742, and 8,952,769 assigned to the assignee of the present invention, the disclosure of each which is hereby incorporated by reference into the present application for all purposes.
The filter may operate in dual mode (e.g., HE11 mode) and each cavity of the filter may be coupled to at least one adjacent cavity via a respective aperture (or “iris”) that enable the HE11 field to couple between the cavities. The iris may have a slot-like form factor with a large aspect ratio of length to width. The iris may be disposed in a central portion of a common wall separating two adjacent cavities. The iris should be optimally sized in order for the filter to meet specified requirements. The optimal dimensions are difficult to predict. Moreover, dimensional variations resulting from machining tolerances can significantly affect filter performance.
In the absence of the present teachings, fabrication and testing of multiple common walls, each including an iris, the irises each varying slightly in size, may be necessary to find an iris size that provides the best performance.
The present inventors have appreciated that electrical/magnetic coupling between adjacent cavities of a multicavity RF filter may advantageously be made adjustable by way of an auxiliary aperture disposed near a perimeter of a common wall separating two adjacent cavities effective area of the auxiliary aperture may be adjusted by way of an externally adjustable tuning screw.
According to some implementations, a radio frequency (RF) dielectric resonator filter includes at least a first cavity and a second cavity, and a first externally adjustable tuning screw. Each cavity is loaded with a dielectric resonator, the first cavity being separated from the second cavity by a common wall, the common wall including a first and second aperture that couple an electromagnetic field between the first cavity and the second cavity. The first externally adjustable tuning screw extends from the second aperture, a portion of the tuning screw being external to the filter. The first aperture is an iris disposed in a central portion of the wall and the second aperture is disposed proximate to a perimeter of the wall. The second aperture has an effective area that is adjustable by the first externally adjustable tuning screw.
In some examples, the iris may have a slot-like form factor. In some examples, the iris may have a square, rectangular, circular or cruciform shape.
In some examples, the filter may include a second externally adjustable tuning screw, the common wall including a third aperture, the third aperture having an effective area that is adjustable by the second externally adjustable tuning screw.
In some examples, the second aperture may be a rectangular slot formed at an edge of the common wall.
In some examples, each dielectric resonator may have a respective longitudinal axis, the respective longitudinal axes being substantially coaxial. In some examples, each cavity may have a respective longitudinal axis and characteristic diameter, the respective longitudinal axes being substantially parallel and separated by a distance greater than the characteristic diameter.
In some examples, the filter may include a multi-cavity metallic housing, the housing comprising a plurality of walls that define a plurality of resonator cavities.
According to some implementations, a multiplexer includes at least two channel filters and a first externally adjustable tuning screw. Each channel filter is a bandpass dielectric resonator filter, including at least a first cavity and a second cavity, each cavity being loaded with a dielectric resonator, the first cavity being separated from the second cavity by a common wall, the common wall including a first and second aperture that couple an electromagnetic field between the first cavity and the second cavity. The first externally adjustable tuning screw extends from the second aperture, a portion of the tuning screw being external to the filter. The first aperture is an iris disposed in a central portion of the wall and the second aperture is disposed proximate to a perimeter of the wall. The second aperture has an effective area that is adjustable by the first externally adjustable tuning screw.
According to some implementations, an improved radio frequency (RF) filter includes at least a first cavity and a second cavity, each cavity being loaded with a dielectric resonator, the first cavity being separated from the second cavity by a wall, the wall including a first aperture that couples an electromagnetic field between the first cavity and the second cavity. The improvement comprises: a second aperture disposed proximate to a perimeter of the wall and a first externally adjustable tuning screw that extends from the second aperture, a portion of the tuning screw being external to the filter. The second aperture has an effective area that is adjustable by the first adjustable tuning screw.
Features of the invention are more fully disclosed in the following detailed description of the preferred embodiments, reference being had to the accompanying drawings, in which:
Throughout the drawings, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the subject invention will now be described in detail with reference to the drawings, the description is done in connection with the illustrative embodiments. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the subject invention as defined by the appended claims.
Specific exemplary embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It will be understood that when a feature is referred to as being “connected” or “coupled” to another feature, it can be directly connected or coupled to the other feature, or intervening e feature s may be present. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. It will be understood that although the terms “first” and “second” are used herein to describe various features, these features should not be limited by these terms. These terms are used only to distinguish one feature from another feature. Thus, for example, a first user terminal could be termed a second user terminal, and similarly, a second user terminal may be termed a first user terminal without departing from the teachings of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. The symbol “/” is also used as a shorthand notation for “and/or”.
The terms “spacecraft”, “satellite” and “vehicle” may be used interchangeably herein, and generally refer to any orbiting satellite or spacecraft system.
Referring to
Referring now to
In the example implementation illustrated in
Input/output coupling device in the form of a probe assembly or connector 413(A) and 413(B) may be used to couple microwave energy from/to an external source (not illustrated) relative to the input/output cavities 420(1)/420(n). For example, microwave energy coupled to a probe 419 may be radiated therefrom into the input cavity 420(1). Microwave energy may be coupled from the input cavity 420(1) into an adjacent intermediate cavity 420(i) by a first aperture 421(1) disposed in a central portion of common wall 403(1). A respective cylindrical dielectric resonator 430 may be disposed in each cavity 420. Each dielectric resonator 430 may be mounted within a respective cavity 420 by one or more insulative mounting elements (not illustrated) that may take the form of pads or short columns of low loss insulator material such as polystyrene or rexolite, for example.
Each dielectric resonator 430, together with the respective cavity 420 within which it is disposed, may form a composite resonator having axial symmetry. In some implementations, one or more cavities 420 have an associated one or more tuning screws 429 that project into the cavity. At least some common walls 403(i) may include, as illustrated, an auxiliary aperture 440(i). Similarly to iris 421(i), the auxiliary aperture 440(i) may provide a coupling of microwave energy between adjacent cavities sharing common wall 403(i). The magnitude of the coupling may depend on an effective area of the auxiliary aperture 440(i). An effective area of the auxiliary aperture 440(i) may be varied by controlling a penetration depth of an adjustable tuning screw 450(i). As a result, the characteristic bandwidth of the coupling between two adjacent cavities can be adjusted and optimized notwithstanding that the dimensions of the iris 421(i) may be nonadjustable and not necessarily optimal.
The presently disclosed techniques may also be adapted to a multicavity microwave filter in which dielectric loaded cavities are arranged in a side-by-side manner as described in U.S. Pat. No. 5,608,363, incorporated herein by reference in its entirety for all purposes and U.S. Pat. No. 8,907,742. For example, referring to
Each channel filter 700(i) may be configured to output RF energy at a respective wavelength λi. For example, channel filter 700(1) may be configured to output RF energy at a wavelength λi.
One or more of the respective channel filters 700 may be a multi-cavity RF filter configured as described hereinabove. More particularly, one or more of the channel filters 700 may include a common wall disposed between two adjacent cavities, the common wall including a centrally disposed aperture, and an auxiliary aperture, the auxiliary aperture having an effective area that is adjustable by way of an externally adjustable tuning screw.
Thus tunable irises for a dielectrically loaded microwave filter have been disclosed. The foregoing merely illustrates principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody said principles of the invention and are thus within the spirit and scope of the invention as defined by the following claims.
