Rejection Band Enhancement of Compact Double-Layered Dual Band BPF Using Stepped Impedance DGS

Recently, A design technique of compact dual band bandpass filter is developed using a double-layered technology. To show the potential of this technique and increase the filter capability, the proposed dual band filter is modified with ultra-wide stopband performance in this article. Indeed, a stepped impedance resonator (SIR) is realized and patterned in a DGS closed to the input/output feeding ports. To achieve that properly, the characteristic frequency of the suggested SIR is analyzed using even-odd method and its dimensions are calculated at the unwanted spurious frequency (f
s
). To improve the above concept, a dual band BPF working at 2.4/3.5 GHz is designed, simulated, and measured for multi-communication system purposes. The filter responses from simulation and measurements are compared and discussed. Consequently, the final modified filter is accomplished with a rejection band performance better than19 dB up to 10 GHz.