Multimode directional filter for millimeter range receivers

Summary form only given. In the development of high sensitivity mixer receivers within a broad tuning range, the problem occurs of supplying the local oscillator (LO) power to the mixer. The construction which allows the input both of the signal and LO power must provide their minimal losses because of the low LO power usually used. To suppress the LO noise, it is necessary to supply the LO power in the narrow frequency band which is formed by a high quality resonator. The multimode directional filter represents an improved solution to the problem of the LO injection to MM-wave receivers. The filter shows reasonably good electrical and mechanical performances in a 30% frequency band. The filter directional nature together with its resonant character provide both the low signal direct losses and the LO passage losses within the wide tuning range (85-115 GHz). The multimode resonator also gives a high signal-LO frequency separation. The filter was used as a diplexer in 3 mm range receivers.