At&t Bell Laboratories

Bell Telephone Laboratories

Arlen K Johnson

Thomas Peter Tignor

Peter S Rha

Theodore K Wingard

Gary D Stuck

An interdigital resonant cavity filter structure is foled to provide two adjacent chambers physically positioned side by side and electrically connected in series with each other. A center plate divides the two chambers with a slot at one end of the structure to permit the two chambers to function as one resonant cavity in a folded relation to each other. Each chamber includes interdigital resonators which are related to the overall resonant cavity to produce a band pass filter action within the folded resonant cavity. The input of the filter structure is applied through a port of a circulator connected to one end of the resonant cavity and the output is taken from another port of the circulator. The opposite end of the resonant cavity is terminated in the characteristic impedance of the resonant cavity thereby causing the overall structure to operate as a high quality notch filter.

Folded interdigital notch filter

Microwave devices are fabricated by a method wherein a block of dielectric material is conformed to the physical configuration of a required microwave device, and it is then coated with electrically conductive material. Portions of the coating material are removed from predetermined regions of the block to implement a predetermined microwave device. One microwave device fabricated in accordance with the foregoing method is shown, and comprises an interdigital bandpass filter in which the block is shaped and drilled with a line of parallel holes to define the physical configuration of an interdigital filter in which the interiorly-coated drilled holes comprise resonator rods within a microwave cavity formed by the exteriorly-coated remaining portions of the dielectric material block. Coating material is removed from end portions of the rods formed by the coated holes in order to fine-tune the filter to a desired center frequency in the band of operation.

Microwave circuit device and method for fabrication

Compactness and substantially optimum electrical performance are realized in a microwave filter incorporating a housing (21, 22) including an interior surface that forms an enclosed cavity having planar cross sections substantially elliptical in shape (FIG. 3). At least one axis of each ellipse monotonically increases in length with perpendicular distance from a first surface (23) toward a second surface (24). A dielectric resonator (11) is positioned in a predetermined relationship within the cavity and at least two terminal members (30,35) extend from outside the housing (21,22) into the cavity. Electromagnetic coupling between the housing (21,22) and the dielectric resonator (11) is minimized to afford substantially optimum electrical performance of the microwave filter.

Growing community of inventors

New Providence, NJ, United States of America

Arlen K Johnson