Equivalent Circuits of Lossy Two-Port Waveguide Devices

Some equivalent circuits of 2-port lossy devices are discussed in this paper. The main advantage of the proposed circuits is that they are obtained with two positive resistances, while other classic circuits could contain also negative resistances, as it happens in presence of lines in lossy waveguide device. The proposed circuits are two: the first simplifies the identification of the reactive part of the device kernel (``classic" circuit) while the second simplifies the resistive part (``compact" circuit). The key of the identification is the presence of two input/output lines with proper lengths that permit to realize the first or the second simplification. Both circuits are able to identify correctly any lossy 2-port waveguide device and can help the designer in the analysis of the effect of the losses due to the components of the device. The ``compact" circuit seems to have more promising developments in the design of filters/multiplexers.