Lossy inverters and their influence on coupled resonator filter characteristics

Lossy inverters have been used recently to describe circuits with lossy couplings. The subject is important for microwave filters design as well as for coupled transmission lines analysis and measurements. In this paper it is shown that lossy inverters do not satisfy the passivity condition. They should be considered as active circuits. On the base of coupled dielectric resonators examples new models of lossy coupling have been developed that preserve the passivity condition. The influence of the coupling losses on filter characteristics has been shown. Moreover, the developed models can be easily used to design coupled resonator microwave filters employing the coupling matrix method.