Capacitive Coupled Wide-Notch Stepped Impedance Narrow-Band Bandpass Filter for WiMax Application

Abstract

The development of wireless communication standards necessitates optimal filter design for the selection of appropriate bands of frequencies. In this work, a compact in size pair of parallel coupled symmetric stepped impedance-based resonator is designed with supporting to the WiMAX communication standards. The coupled resonator is tuned to allow the frequency band between 3.4 GHz and 3.8 GHz, which is centered at 3.6 GHz. A parasitic effect of capacitively coupled feed structure is used for exciting the two symmetrical stepped impedance resonators. The bandwidth and selectivity of the filter are enhanced with the change of characteristic impedances and controlling the coupling gap between resonators. This design offers single narrow sharp passband selectivity as well as multiple stopband harmonic suppression arising as a result of multiple transmission zeros. The designed filter operates with a fractional bandwidth (FBW) of 11.47%. The proposed single narrowband bandpass filter provides better suppression in either side of the tuned frequency (3.6 GHz) without degrading the passband performance. Also, this novel filter offers an insertion loss of about −0.08 dB and a return loss of greater than −30 dB in passband. This approach is useful for eliminating unwanted spurious harmonics responses that enter the desired response. The suggested bandpass filter has been simulated using Advanced Design System (ADS) tool, and the measurement has been made using a network analyzer, and the results are reported.