Double-Layer Microstrip Band Stop Filters Etching Periodic Ring Electromagnetic Band Gap Structures

The electromagnetic band gap structure (EBGs) is widely used in microwave engineering, such as amplifiers, waveguides, microstrip filters, due to the fact of its excellent band stop characteristics. In this paper, three kinds of microstrip band stop filters were proposed which were etched with a hexagonal ring EBGs, octagonal ring EBGs and elliptical ring EBGs. Firstly, the etching coefficient of a band stop filter is proposed, and the performance of filters with different etching coefficient was analyzed. Secondly, the equivalent circuit of an EBGs band stop filter is proposed. By comparing the simulation results using advanced design system (ADS) and high frequency structure simulator (HFSS), it was found that the simulation results had the same −10 dB stopband width which verifies the correctness of the equivalent circuit model. Finally, three kinds of microstrip stopband filters were fabricated and measured. The experimental results of the −10 dB stopband width and resonant frequency were in good agreement with the simulation results. The −10 dB stopband fractional bandwidth of the three kinds of microstrip stopband filters was more than 63%. The proposed microstrip band stop filters can be widely used in microwave devices with a wide stopband.