A microwave pulsed attenuator using an r.f.-excited discharge

A new form of microwave pulsed attenuator for use in duplexing systems is described. The use of an r.f.-excited gas discharge avoids many of the problems inherent in other forms of pulsed attenuator and results in a simple, inexpensive and reliable component. One form of attenuator, for the 3000 Mc/s frequency band, is described in detail, and its performance is discussed in relation to the overall system performance of a microwave duplexer. An attenuation of at least 50 dB with a recovery time of 25¿30 microsec to 6 dB is achieved. The bandwidth of the attenuator depends on the number of resonant elements used; with an attenuator consisting of four resonant elements two of which contain discharge tubes, a bandwidth of at least 10% to a voltage standing-wave ratio of 0.85 may be obtained. The insertion loss of the complete attenuator is less than 0.1 dB. The application of the same principles to the design of pulsed attenuators at other microwave frequencies is discussed.