High Power Hopping Filter

This SBIR analyzes approaches for high power VHF hopping filters in which eight filters are used in a multi-coupler configuration so that a single antenna can provide signals to eight SINCGARS radios. Three approaches were studied: 1) a filter with series connected diodes, 2) a filter with shunt connected diodes and 3) a combline filter. A series input L-C bandpass filter is described which can meet the high power, tunability, insertion loss and out-of-band rejection. A series cascade of two filters is used to get the out-of-band rejection. Tuning is done by use of multiple pin diodes/capacitors combination in which the capacitor combinations are selected by pin diode switching. A transient analysis was done to determine the required voltage and current capability for the devices. Devices are available which will withstand the high power, current, and voltage. The multi-coupler provides a switch around the second of the 2-filter cascade to permit improved radio performance. A T/R Switch/limiter circuit prevents the 50 watts from damaging the radios. An analysis done on eight hopping filters in a multi-coupler showed that there was little interaction between the filters.