A low-loss high-reliability microwave switch matrix for smart antenna systems

A new technique for optimizing the design of low-loss bidirectional (n,m) microwave switch matrices is proposed for use in smart antenna systems. Based on Banyan networks as a base-line topology, architecture trade offs are made between routing complexity, component count, reliability, isolation, and insertion loss. It applies to any number of inputs n and outputs m where n and m are a power of 2. Using this technique, a (16,4) 2.4 GHz ISM band microwave switch network was fabricated using 4-layer PCB and RFIC technology. The optimized design uses only 28 transfer switch ICs, which is less than half of the components used in the equivalent cross-point switch architecture. It also permits a one-element failure on the first log₂m stage(s), thus improves system reliability.