Dual Band Microstrip BPF with Controlled Wide and Narrow Pass Bands

Abstract

The proposed work demonstrates reconfiguration of wideband response of multimode resonator to dual band BPF with wide and narrow passbands. The proposed filter comprises of half wave SIR based multimode resonator, with Bowtie radial stub integrated into its symmetrical plane. To attain dual band characteristics from wideband response a new transmission zero is created in wide passband which splits it into wide and narrow passbands. A new transmission zero is procured by Bowtie radial stub. The wide and narrow passbands are centered at 5.5 GHz and 12.5 GHz respectively. To procure flat pass band response, a high impedance Interdigital feed structure is used at input and output. Due to this feed structure, the insertion loss S 21 is at almost 0dB line in first passband. Further by varying the radial angle $\theta_{1}$ of Bowtie stub, both passbands are controlled by manipulating the location of new transmission zero TZ and even mode frequencies in both passbands. From simulation results, the measured return loss S 11 and insertion loss S 21 for the first passband are less than −10dB and 0dB respectively with upper and lower edges of pass band are at −24dB and −30 dB respectively. Additionally, for the second pass band the measured return loss $\mathbf{S}_{11} > -10\mathbf{dB}$ and insertion loss $\mathbf{S}_{21} . Two transmission zeros with attenuation level of - 30dB and −37 dB are found in upper stopband.