A circuit and method for electronically tuning an RF power amplifier. The output filter includes at least one electronically variable reactance. The electronically tuned power amplifier may be tuned rapidly to a selected frequency, to a selected impedance, or to produce a selected output amplitude. An optional controller translates frequency, impedance, or modulation inputs into tuning signals. High-efficiency, wideband amplitude modulation is produced by varying the amplifier load impedance along preferred loci.

Electronically tuned power amplifier

A tri-plate type dielectric filter having a dielectric substrate, a plurality of resonator electrodes embedded in the substrate, and coupling electrodes formed within the dielectric substrate for capacitively connecting the resonator electrodes to provide capacitors between adjacent resonator electrodes. The resonator electrodes may take the form of parallel elongate strips each providing a stripline type λ/4 or λ/2 TEM mode resonance circuit. One end of each strip is exposed at an outer surface of the substrate. This end of each strip is trimmed to adjust the resonance frequency of the resonance circuit.

Dielectric filter having coupling electrodes for connecting resonator electrodes, and method of adjusting frequency characteristic of the filter

A multiport radio frequency (RF) signal combiner is described for combining three or more RF signals for application to an antenna. The combiner includes an input port for each RF signal, an output port coupled to the antenna, and a tuning port coupled to a tuning transmission line. The input ports, output port and tuning port are connected to a terminating element. The tuning transmission line is terminated by a fixed or adjustable short-circuit impedance for substantially eliminating the capacitive discontinuity created by interconnecting the input ports. The RF signal combiner can be advantageously utilized in any radio system where it is necessary to multiplex the RF signals from three or more transmitters to a single antenna.

Multiport radio frequency signal combiner

A multi-layered coupling device (FIG. 9) for coupling radio frequency (RF) energy on a transmission line (302) to a coplanar coupler. The coupling device includes a first coupling structure that is coplanar with the transmission line (302) and parallel plate structure (304) positioned a predetermined distance in a plane parallel to the transmission line (302). The parallel plate structure (304) is not physically connected to any other structure through the use of vias or the like. The parallel plate structure (304) is used to increase the coupling coefficient and directivity of the coplanar structure by being divided into a plurality of segments with varying dimensions to better control coupling capacitances.

Multi-layered bi-directional coupler utilizing a segmented coupling structure

An output transistor of an RF power amplifier remains stable so that it does not generate subharmonic spurious outputs. An adaptive stabilization network maintains the stability of the output by decreasing the impedance presented to the output transistor when voltage levels at the output transistor exceed a predetermined level. A combination consisting of a peak detector coupled to a Zener diode senses the predetermined level. A PIN diode couples to the Zener diode and to the output transistor so that the PIN diode becomes forward biased when the predetermined level is exceeded.

Philip L Clar

Papers

Microstrip-microwave coupler

Broadband single pole multi-throw diode switch with filter providing matched path between input and on port

Transistor protection circuit