Abstract: An external motor is coupled to a tuning rod extending into a resonant cavity of a transmitter combiner. A microprocessor tuning control system generates motor control signals that cause the motor to rotate the tuning rod, varying the resonant frequency of the cavity so as to minimize the reflected power from the cavity. Incident and reflected power are detected by diodes in the transmitter cable connecter of the cavity. The standing wave ratio is computed and composed with a threshold value to determine if the cavity needs to be retuned. The microprocessor effectuates reading of digital numbers representing the incident and reflected power and makes a "best effort" attempt to tune the resonant frequency of the cavity to the transmitter frequency, using the motor to rotate the tuning rod.

Abstract: A duplexer includes an integral interdigital transmitter filter and parallel interdigital receiver filter in a common housing. A three-quarter wavelength antenna transformer section couples rf energy from the transmitter filter to an antenna and also couples rf energy from the antenna to the receiver filter and to an antenna cable connector.

Abstract: A transmitter combiner includes a plurality of adjacent square prism filters, each of which shares at least one square wall with another of filters. Tuning of the individual square prism filters is accomplished by adjusting the position of tuning rods located in the high electric field region of each cavity. Tuning of each filter is achieved by rotating a control rod perpendicular to and extending through a rectangular end wall to pivot the tuning rod in that filter. In one embodiment of the invention, the control rod extends through a conductive tube attached along a square wall of the filter and perpendicular to the rectangular wall. In another embodiment of the invention, the control rod extends from the center of the rectangular wall and supports the tuning element near the center of the cavity. Temperature compensation is accomplished by variation in the length of the control rod as a function of temperature to compensate for changes in the dimensions of the cavity with the temperature thereof.

Abstract: A duplexer includes an integral interdigital transmitter filter and parallel interdigital receiver filter in a common housing. A three-quarter wavelength antenna transformer section couples rf energy from the transmitter filter to an antenna and also couples rf energy from the antenna to the receiver filter and to an antenna cable connector. The receiver filter selectivity is improved by providing a notch resonator between a receiver transformer section and the housing, and the transmitter filter selectivity is improved by providing a notch resonator between a transmitter resonator and the housing.

Abstract: A microwave tuned cavity has a strip of temperature sensitive bi-metallic material plated with silver attached at one end to the inner surface for the tuned cavity and having its other end extending at an inclined angle to the center of the volume bounded by the inner surface of the tuned cavity. The housing of the tuned cavity expands as its temperature increases, tending to cause the resonant frequency of the cavity to decrease. The strip of bi-metallic material bends slightly as the temperature increases, causing its free end to move toward the surface on which the strip is mounted. This decreases the amount of capacitive loading of the resonant signal in the cavity, tending to increase the resonant frequency caused by thermal expansion of the housing. When the temperature decreases, the free end of the bi-metallic strip moves slightly toward the center of the cavity, thereby compensating for slight thermal contraction of the walls due to the decrease in temperature.

Abstract: A cubical device includes six square sides connected to form a cube. Each side has an electrically conductive inner surface electrically connected to the other inner surfaces. A plurality of electric field probes attached to coaxial connectors centrally mounted on respectively perpendicular sides of the cube extend into the volume bounded by the cube. In one embodiment of the invention, three opposing pairs of electric field probes extend into the volume from opposite sides of the cube. The electrical cube then functions as three independent bandpass filters, each having a "Q" determined by the volume. In another embodiment of the invention, an output probe extends into the cavity at a predetermined angle and senses the standing wave patterns produced in response to the electric field probes, whereby the cubical apparatus functions as a bidirectional combiner for up to three channels.

Abstract: Disclosed is an improved ferrite circulator particularly adapted for use as an isolator in VHF and UHF transmission systems. It comprises a pair of relatively thick ground plates to which are attached three or more equally spaced coaxial connectors forming circulator ports. A pair of elongated magnetic members extend between the ground plates from opposite sides of the circulator junction to a location between the ground plates remote from the junction. A resilient permanent magnet is movable between the magnetic members at the remote location to provide simple and rapid tuning by adjustment of the permanent magnet field across the junction.