Abstract: A bandpass filter having 4-degrees of freedom includes a plurality of resonant cavities having respective Qs where at least one of the Qs is different. A plurality of main couplings couple successive resonant cavities to establish a main signal path that provides a first degree of freedom for controlling the shape of the filter's frequency response over its passband. A plurality of bridge couplings couple pairs of the resonant cavities so that the cavities are connected in a canonical circuit topology. The bridge couplings provide second and third degrees of freedom for controlling the sharpness of the frequency response 's transition between its passband and stopband and controlling the linearity of its phase, respectively. The cavities' non-uniform Qs provide a fourth degree of freedom for controlling the amplitude of the filter's frequency response in the passband so that the amplitude is within a predetermined tolerance of a desired passband shape.

Abstract: A high performance bandpass filter is produced by adding one or more "simultaneous couplings" to a conventional resonant cavity filter. A "simultaneous coupling" is created when a filter's input or output signal, normally coupled to a filter's first or last cavity respectively, is coupled to one or more other cavities. Each simultaneous coupling causes a finite-frequency insertion loss pole to be created, which produces a quasi-elliptic frequency response on its side of the passband. These poles may be placed on the left and/or right sides of the passband, so that both symmetric and asymmetric quasi-elliptic frequency responses are realizable. A diplexer constructed from two such bandpass filters has the extremely sharp selectivity provided by two asymmetric bandpass filters, thus providing a high degree of receive/transmit isolation.

Abstract: A microwave cavity filter (30, 30A) is formed of a section of waveguide (36, 114) terminated by end walls (38, 40, 44, 166, 168, 176) to form cavities (32, 34, 32A, 34A) wherein ridges (100, 102, 118, 120) are disposed longitudinally within a cavity and extend from the cavity wall partway to a central region (104, 124) of the cavity. In a preferred embodiment of the invention, the ridges are disposed symmetrically about a central plane (144), each ridge having a first component (106, 122) perpendicular to the central plane and a second component (108, 126) parallel to the central plane. A cross-sectional shape of a filter cavity may approximate a semicircle wherein one wall section (88, 130) of the filter cavity is disposed within a diametric plane (216) of the cavity. The end walls of the cavities may be constructed as iris plates with apertures (82, 182, 184, 186, 190) for coupling energy of selected modes of electromagnetic resonance within the respective cavities.

Abstract: A microwave filter is composed of a set of circular cylindrical cavities arranged in cascade array and interconnected by irises having cross-slotted apertures for coupling electromagnetic power in two orthogonal TE.sub.113 modes. An input port is formed in a first of the cavities and an output port is formed in a last of the cavities. Each port is constructed as a transition between a section of rectangular waveguide and a section of circular waveguide, the section of circular waveguide being a portion of the first cavity and the last cavity, respectively, in the input and the output ports. The cross-sectional aspect ratio of the rectangular waveguide is 2:1. The ratio of a diameter of the cavity to length, as measured along a cylindrical axis in each cavity, is 0.26 thereby to provide for increased bandwidth while minimizing dispersion and transmission loss.

Abstract: The present invention provides an improved microwave integrated circuit filter for electromagnetic waves. The filter includes a waveguide and three, four or more resonators spaced from one another and extending from the waveguide. Means, which may include a conductive ribbon, are provided electromagnetically coupling nonadjacent resonators.

Abstract: An electromagnetic filter assembly comprises a transmission line electromagnetically coupled to a dual mode resonator having a means for differentially tuning the two modes. The filter may be incorporated in a microwave integrated circuit, and the tuning means may be a movable dielectric slab asymmetrically disposed on the resonator.

Abstract: A tri-mode spherical cavity microwave filter comprising two tandemly disposed generally spherical bodies each of which defines a spherical cavity which supports three identical, mutually orthogonal modes of electromagnetic energy, a cavity coupling aperture connecting the cavities, a plurality of cavity tuning holes, and a plurality of coupling tuning holes. One of the spherical cavities has an input aperture, and another has an output aperture. The cavity tuning holes and coupling tuning holes are adapted to receive cavity tuners and coupling tuners, respectively.

Abstract: A folded end-coupled general response TE.sub.011 filter is herein described which achieves all bridge couplings necessary for general bandpass response in a particularly convenient two-tier overlapping structure, where all couplings are made in a single removable iris, and where probe and/or slot couplings are used to achieve coupling of either sign.

Abstract: There are herein described evanescent mode filters each of which include a hollow waveguide, wherein a plurality of resonators are disposed, the resonators including loading structures such as tuning screws, for example, wherein at least one of the loading structures is angularly disposed, relative to the axis of the waveguide, with respect to others of the loading structures to reduce the length of the filter and/or to provide internal bridge couplings.

Abstract: A conical scan microwave antenna having a stationary fixed axially symmetric primary reflector consisting of any concave surface of revolution along with a spherical wave point source feed-and-subreflector assembly potentially rotatable about the axis of the primary reflector, and with the surface of the subreflecror being shaped so that the reflection of the spherical wave from the feed and off of the subreflector strikes the primary antenna and is reflected as a co-planar wavefront from every point on the primary reflector, and, further, the subreflector-and-feed assembly is located outside of the aperture of the reflected pencil beam such that for any given scan position of the subreflector, no portion of the reflected wavefront intersects the subreflector or its feed.

Abstract: An active microwave filter for use in both bandpass and notch filter applications is herein described, the filter incorporating a distributed resonator to which is coupled an amplifier which provides a positive feedback and cancels the net dissipation in the resonator.

Abstract: There is herein described a microwave coupled-cavity filter having adjacent cavities defined by spaced end walls disposed in a tubular side wall, the end walls including at least one pair of oppositely disposed coupling apertures extending radially from the side wall toward the center of the associated end wall, and at least one of the associated pair of the coupling apertures containing a tuning screw extending through the side wall for precisely adjusting the coupling between adjacent filter cavities.

Abstract: A waveguide filter is herein described that employs a resonator ordering which allows a direct realization of all canonical couplings while retaining the advantages of a standard dual mode filter, the filter including a reflective plate in one end cavity and both input and output ports in the other end cavity, where one of the ports is a shunt port in a sidewall of the cavity structure and the other port is a coupling slot in the outer end wall.