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 topologie s of active recursive filters can be effectively minimized by using appropr iate unbalanced power dividers/combiners and an amplifier, A comparison bet ween the different topologies is given, Simulations and practical results a re presented and validate our approach. In a second part, the noise wave fo rmalism is applied to lambda/2 microstrip active filters. We show how the a ppropriate choice of coupling between lines and resonators can achieve low- noise filters. Simulations and practical results are also presented.