Design and Analysis microstrip dual-band bandpass filter with tunable bandwidth and center frequency

This paper introduces a novel microstrip dual-band bandpass filter that combines a stepped impedance resonator (SIR), parallel stubs and asymmetric input and output ports on both sides. This configuration can lead to desired frequency characteristics like central frequency and required band passes. The required bandwidths will be optimized by stepped impedance resonator and the return and the insertion losses by the parallel stubs on both sides of the structure. Finally, we obtained a suitable isolated frequency response between the two passes bands by making asymmetric the location of the input/output port on the sides. For design and manufacturing a dual-band filter with 4.7 GHz and 7.16 GHz frequencies with the same 87 MHz bandwidth in each band, a suitable structure is proposed and used. The circuit analysis of the filter is performed section by section, to better examine results. The simulation and test results of the proposed structure indicate a 0.92 and 0.45dB insertion loss and 21 & 24.31 dB return losses in the two bands. In the following, we show by changing the dimensions of the middle stubs, the central frequency and bandwidth of the filter can be tuned. The main features of this filter are compact size, dual bands, and proper passing bands isolation.