Optimization of noise performance for various topologies of planar microwave active filters using noise wave techniques

In this paper, two types of microwave active filters are studied. First we show how, using a noise wave formalism, the noise factor of three topologies of active recursive filters can be effectively minimized by using appropriate unbalanced power dividers/combiners and an amplifier. A comparison between the different topologies is given. Simulations and practical results are presented and validate our approach. In a second part, the noise wave formalism is applied to /spl lambda//2 microstrip active filters. We show how the appropriate choice of coupling between lines and resonators can achieve low-noise filters. Simulations and practical results are also presented.