Varactor-Tunable Four Arms Star Bandstop FSS With a Very Simple Bias Circuit

In this paper a varactor-tunable bandstop FSS based on the four arms star geometry is presented. Besides the resonant frequency tuning, an interesting feature is that practically no bias circuit is required. The four arms star geometry is described, including initial design equations. The adopted varactor model is depicted. A FSS prototype is designed, fabricated and characterized, with numerical and experimental results, observing a good agreement. Despite the simplicity of the considered varactor model, the difference of 6.5% between numerical and experimental results, could be easily decreased, adapting the capacitance value, but this fine adjust it is not the objective of this work. The varactor-tunable bandstop FSS prototype achieved a resonant frequency varying from 3.4 GHz to 3.8 GHz. With the herein proposed FSS, using appropriate varactors and basic cell dimensions, different resonant frequency ranges can be obtained, a very attractive characteristic, with potential applications in the current telecommunication systems.