Abstract-In this paper in order to reduce the size and improve the performance of microwave filter, novel single and dual band matched band-stop filters are developed. A stepped impedance dual mode resonator is used, resulting in a much more compact size, than the conventional dual mode ring resonator that has an electrical length of 360 • . The proposed prototype is able to achieve high stop band attenuation even with low Q factor values. Moreover, for the short electrical length of this filter, the first spurious resonance occurs at 4.7 times the fundamental resonance frequency. Therefore, the proposed technique selectively removes only the fundamental resonance frequency when such a resonator is implemented. A theoretical analysis, along with an experimental prototype is proposed in order to demonstrate the feasibility of these proposed networks.

Electronically switchable microwave filters are attracting more attention for research and development because of their importance in increasing the capability of wireless communication and cognitive radios. In this paper, novel switchable microwave bandstop to all pass filters are designed by using stepped impedance resonator. Commercially available Pin diodes are used in order to allow the fastest switching between band-stop and all pass responses. The theoretical analysis is presented in this paper, and its feasibility has been experimentally verified with a micro-strip prototype. The design was also characterized by measuring the filter performance with increasing power levels of 20, 15, 10, 5, and 0 dBm. The results have shown that the switchable filter is immune to power saturation effects. Nonlinear measurements at higher power levels are also performed and the switchable filter produced low power inter-modulation product. The main advantage of this filter is its capability to switch between band-stop and all pass mode of operation. Other advantages include being small in size, and low in cost.