MIC Broadband Filters and Contiguous Multiplexers

A novel design and construction technique for Microwave Integrated Circuit broadband filters and a contiguous multiplexer is presented together with experimental results on a number of devices. The multiplexer is formed from a cascade of diplexers each containing a highpass and lowpass filter. Based on the generalised Chebyshev prototype, selective low loss microwave filters for these diplexers are designed having new suspended substrate configurations. Octave bandwidths are achieved for the highpass channels. The contiguous multiplexer has three outputs 4-8 GHz, 8-12 GHz and 12-18 GHz and is constructed on a single substrate approximately 2" × 1¼". Experimental results show each channel has low passband loss and highly selective responses at bandedges and the multiplexer will meet the normal environmental conditions. Also, due to the printed circuit realization, a high degree of population tracking can be readily achieved.