Abstract: A waveguide lowpass filter has successive groups of three separate ridges spaced longitudinally in said filter. A center ridge of each filter has a larger cross-sectional area than two side ridges which are the same size. All ridges are parallel to one another in a longitudinal direction. The groups are associated with shunt capacitances and the spaces between adjacent groups are associated with series inductances in an evanescent mode. In operation, the filter is capable of supporting a TE.sub.10 mode in the passband and three modes, TE.sub.10, TE.sub.20 and TE.sub.30 in the stopband. The filter has a relatively high power handling capability as compared to previous evanescent mode lowpass harmonic filters.

Abstract: A Beam-forming Network includes a plurality of directional couplers and phase shifters and which can interconnect both a transmitter and a receiver to the same group of radiating elements of an antenna even though the transmitter frequency band is different and well spaced from the receiver frequency band. This is accomplished, in accordance with the invention, by using directional couplers each of which has a variable response over a wide band of frequencies but which is designed so that its response over the transmitter frequency band is stable and its response over the receiver frequency band is also stable.

Abstract: A bandpass filter has a plurality of cascade cavities that operate in a dual-mode and are mounted in a planar relationship to one another. Each cavity contains a dielectric resonator and resonates at its resonant frequency in two HE.sub.11.delta. modes. An iris is located between adjacent cavities and contains an aperture that can independently control inter-cavity coupling. The dielectric resonator is cylindrical in shape and an adjustable metallic plunger is located in a wall of each cavity so that the cavity can be tuned over a relatively broad range. The filter has good mechanical and thermal stability as well as being extremely flexible in the arrangement of cavities.

Abstract: A waveguide lowpass filter operates in at least two evanescent modes. The filter has successive ridges with a space between said ridges. The ridges are associated with parallel capacitance and a space between them is associated with series inductance in the TE.sub.10 mode. Each ridge is top-loaded so that series capacitance can occur in a TM.sub.11 mode in parallel to said series inductance. The filters of the present invention can be made smaller than previous evanescent lowpass filters and can achieve improved results.

Abstract: An odd order bandpass filter has at least one cavity resonating at its resonant frequency in three independent orthogonal modes. The filter has at least one feedback coupling that is made to resonate and change sign at a center frequency. When the filter has two cavities, one being a triple cavity and the other being a dual mode cavity, the filter can be operated to achieve an elliptic function response. Also, the filter of the present invention can achieve a weight and volume reduction when compared to six-pole dual mode filters.

Abstract: A bandpass filter has a plurality of cascade wave-guide cavities each resonating in three independent orthogonal modes. The cavities can be cylindrical or have a square cross-section. Where the cavities are circular, each cavity resonates in TE.sub.111 or TE.sub.010 modes simultaneously. Where the cavities have a square cross-section, each cavity resonates in TE.sub.011 and TM.sub.110 modes simultaneously. Between each triple-mode cavity, there is located an iris having an aperture with four separate radial slots that are offset from a center of the iris. The filter is capable of producing an elliptic function response. In a variation of the invention, an allpass filter has an output that is short circuited and, when used in conjunction with a circulator, it functions as a group delay equalizer. Previous triple-mode filters are not capable of producing an acceptable result relative to dual-mode filters.

Abstract: A bandpass filter has a plurality of cascade waveguide cavities each resonating in three independent orthogonal modes. The cavities can be cylindrical or have a square cross-section. Where the cavities are circular, each cavity resonates in TE.sub.111 or TE.sub.010 modes simultaneously. Where the cavities have a square cross-section, each cavity resonates in TE.sub.011 and TM.sub.110 modes simultaneously. Between each triple-mode cavity, there is located an iris having an aperture with four separate radial slots that are offset from a center of the iris. The filter is capable of producing an elliptic function response. In a variation of the invention, an allpass filter has an output that is short circuited and, when used in conjunction with a circulator, it functions as a group delay equalizer. Previous triple-mode filters are not capable of producing an acceptable result relative to dual-mode filters.

Abstract: A multiplexer has a plurality of bandpass filters coupled through E-plane or H-plane T-junctions to a waveguide manifold. Where the multiplexer has four channels and each filter is a six-pole filter, two triple mode cavities make up each filter. Where each filter is a five-pole filter, one triple cavity and one dual mode cavity makes up each filter. Two band edge channel filters are operated to produce an asymmetrical filter function response, thereby causing extra transmission zeros to be created and improving the selectivity of the filter out of the passband. The multiplexer is designed for use in satellite communication systems and can have a reduced volume and weight when compared to previous multiplexers without any sacrifice in electrical performance.

Abstract: A bandpass filter 8 has a plurality of cascaded wave-guide cavities 11, 12 1N and inter-cavity coupling means 36, 37. One or more of the cavities 12, 1N is rotated relative to an input reference mode 52. The rotation causes quasi-orthogonal coupling structures to be introduced into said cavities 11, 12 1N. The rotation of one or more cavities enables symmetric or asymmetric amplitude and phase responses to be produced as desired.The filter can be used in channel multiplexers for satellite communication systems.

Abstract: A resonant microwave cavity 2 has a bi-metal end cap 4 or a tri-metal end cap 26. The end caps 4, 26 include irises 10, 28. The end caps are affixed to walls of the cavity 2 in the usual manner. As temperature varies, the end caps or irises expand into or out of the cavity to compensate for the increase or decrease in length of the cavity walls due to variations in temperature. The internal volume of the cavity is maintained substantially constant. When a bi-metal end cap is used, each layer of metal has a different coefficient of expansion. When a tri-metal end cap is used, the center layer has the highest of coefficient of thermal expansion.

Abstract: The invention relates to a broad bandwidth frequency divider which converts a band of input frequencies into a band of output frequencies such that each output frequency is one half the corresponding input frequency. The frequency divider has a first rectangular waveguide which propagates the band of input frequencies and a second larger rectangular waveguide which propagates the band of output frequencies. The two waveguides are orthogonally disposed with respect to one another and are interconnected by a slot provided in a common wall. Two nonlinear capacitive reactances are mounted in the first waveguide, one on each side of the slot, forming a transverse resonator. When the two nonlinear reactances are pumped in phase at the input frequency, parametric subharmonic resonance can be excited transversely at one half the input frequency such that the nonlinear reactance voltages are 180.degree. out of phase at the output frequency.