Actively compensated planar ring resonator structures suitable for bandstop and bandpass filters

In this paper the design of bandstop and bandpass filters is studied by means of algebraic manipulations using theory of recursive filters. The objective of these analytical investigations on recursive type functions is to find novel topologies suitable for frequency tuneable bandstop or bandpass responses using only coupled planar ring resonators and amplifiers. We show how the noise factor of this category of filters can be analytically derived and effectively minimized by using appropriate unbalanced power couplers and amplifiers. We validate our approach with simulated examples for each topology.