Design techniques for a low loss 30 channel multiplexer are proposed. The Navy has a requirement for such a multiplexer in the 30 - 88 MHz frequency band for use in eliminating interfering signals in the receiver passband. Design approaches including L-C filters and combline filters are considered. Use of L-C filters will not meet the loss requirements. Proposed is an assembly of 30 round rod combline filters which have sufficiently high Q to meet the loss requirements. Techniques to be investigated include use of cross-coupling to improve out-of-band rejection without increasing pass-band loss. Design techniques for multiplexing the filters are discussed and an approach recommended which will allow the performance requirements to be met.
Benefit: Multiplexers with a large number of channels offer improved performance over those with only a few channels. The availability of a multiplexer with such a large number of channels will find application in receivers where such performance improvement has not been available heretofore.
Keywords: combline filter, combline filter, L-C filter, Multiplexer
