Three-Port Frequency-Selective Absorptive Limiter

This letter describes a novel three-port absorptive limiter for frequency-selective circuits based on a configuration similar to a conventional 90° hybrid coupler. This circuit uses the switching behavior of common diodes to change between the nonlimiting and absorptive limiting states. Theoretical descriptions and designs are presented along with prototypes based on PIN diodes. Measurements of the limiting performance of the devices at approximately 2 GHz as a function of power demonstrate the viability of the concept.