RS Microwave has developed a double diplexer for the GPS L1 and L2 channels. In this device, P/N 63491A-1, the L1 channels and L2 channels are passed, while energy below, above....and between....the channels is rejected. Using network synthesis and optimization following E-M simulation, the common coupling between the two bandpass filters is modified to provide essentially an open circuit condition for the second filter, over the passband of the first filter. In this way, each filter is well-matched within its passband while presenting no mismatch to the opposite filter within its passband.
This technique can be applied to other situations, as well. For example, it is possible to diplex at one end while switch-selecting at the other end. It is also possible to embed gain blocks into these assemblies, compensating for the switching losses. The use of a combination of network synthesis and E-M simulation as used at RS Microwave will no doubt result in the development of new combinations and configurations which would not have been practical in the near past, and thus enable increased utilization of that most valuable of commodities: spectrum.