Design and Analysis of Parallel-Coupled Line Bandpass Filter

Abstract A compact microwave parallel coupled line resonator seventh order bandpass filter (BPF) is presented in this paper, consist a 8-parallel coupled line pairs designed for a maximally flat response or Butterworth response at a center frequency of 2.44175 GHz and with a fractional bandwidth, ∆= 0.035. The filter was implemented in a microstrip platform with a permittivity of the substrate Er=4.4 and a substrate height h=1.5mm. The physical parameters of the parallel coupled line filter sections were optimized using the Microwave Office software to provide the closest values of the bandpass filter prototype values and electrical lengths for a given set of filter specifications. The simulation of direct calculation, show the attenuation S11 response was observed at 2.44175 GHz with a value of -25 dB and the corresponding Insertion Loss S21 is 1.8dB while the optimized design S11 response at the centre frequency with a value of -113 dB and the corresponding Insertion Loss S21 is -2.2dB.