Microwave integrated circuit 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. Basedon 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 high pass channels. The contiguous multiplexer built has three outputs 4 - 8 GHz, 8 - 12 GHz and 12 - 18 GHz and is constructed on a single substrate approximately 2" x 1 ¼”. Experimental results show each channel has low pass band loss and highly selective responses at the bandedges and the multiplexer will meet the normal environmental conditions. Also, due to the printed circuit realisation, a high degree of population tracking can be readily achieved. Detailed computer analysis of the devices is presented and results are in very close agreement with the experimental results. Suitable constructional techniques are developed so the final multiplexer could be manufactured on a commercial basis.