Ultra-broadband frequency discriminator designs for IFM receivers

Instantaneous frequency measurement (IFM) has been widely used in ESM systems for many years and now even low cost radar warning receivers (RWR) are being designed to include IFM modules. Coverage of the normal 2-18 GHz RWR range is normally achieved by band splitting into narrower bands, typically 2-6 and 6-18 GHz each having its own IFM receiver. The added expense of multiple IFMs is justified where dense signal environments are expected, however, in many applications the probability of pulse coincidence is low and the cost and weight savings of a single band IFM would offer the ideal solution. In addition, the availability of ultra-wideband distributed amplifiers with good frequency flatness and limiting characteristics provides a good incentive to develop a single band 2-18 GHz discriminator. The paper describes an alternative discriminator structure which can be designed to cover ultra-wide frequency ranges for use in IFM receivers. The printed structure is highly reproducible and requires no tightly coupled circuit elements