A systematic approach for the development of wide band band pass filters using resonators

Abstract

In this paper, for the first time a novel and systematic approach is presented to construct a wideband Band Pass Filters (BPFs) with high selectivity and stopband response. Two BPFs (Filter I and Filter II) were built on a Taconic (TLX-9) substrate using semi-circular tapered coupled lines, Defected Microstrip Structures (DMSs), Defected Ground Structures (DGS), and Stepped Impedance Resonators (SIRs). The precision of the design procedure is confirmed through 3-D full wave Electro-Magnetic (EM) simulation software where two wideband filters were designed for L, S, and C-bands. Additionally, parametric analysis has been done to evaluate the performance of both wideband filters with key features such as return loss, insertion loss, Band Width (BW), selectivity, and stopband response. Even-odd mode analysis has been implemented using the ABCD matrix that acts as a source for mathematical analysis of Filter I. Eventually, two wideband filters have been fabricated and tested for their effectiveness, and the measured results of two wideband filters are in line with the simulated ones with slight deviations due to fabrication tolerances and connector losses. The prototyped Filter I functions as a bandpass in the frequency range of 2.4 GHz to 4.8 GHz with a maximum insertion loss of 0.85 dB and return loss of 19.5 dB thereby providing 64% Fractional Band Width (FBW). Near 19 dB rejection is observed in the lower and upper stopband regions with BW (stopbands) greater than 2 GHz. Moreover, Filter II is also fabricated and tested. The experimental return loss of 20 dB and insertion loss (maximum) of 0.73 dB over the passband (1.9 GHz to 3.4 GHz) were found with 0.7 Selectivity Factor (SF). More than 20 dB attenuation of stopbands (lower and upper) was achieved. Thus, the fabricated wideband BPFs operate in L, S, and C-bands for radars, satellite and long-distance radio communications, and military telemetry applications.