Design and Analysis of Wideband and Narrowband Substrate Integrated Waveguide Cavity Bandpass Filter for C and X Band Applications

Abstract

Microwave filter is essential in communication systems such as radar communication, newlinecellular radio communication, and satellite communication. The advancement newlineof modern communication systems requires microwave filters that utilize highperformance, newlinecompact size, and low insertion loss bandpass filters. Considering the newlineabove criteria, this thesis describes the design of substrate integrated waveguide wide newlineand narrowband bandpass filters that utilize CSRRs and U-shaped slotline resonators. newlineThe first SIW wideband BPF of the third order is loaded with two u-slot stepped resonators, newlineand CSRR is designed for C band applications. The cavity loaded with stepped newlineresonators (R1 and R3) alone does not make a good selectivity on the lower out of band. newlineHence, the CCSRR is introduced between the stepped resonators (R1 and R3) to improve newlinethe filter s selectivity and enhance the filter s bandwidth. The introduction of CCSRR newlineenhances the selectivity on the lower out-of-band at 5.5 GHz, and the extra pole increases newlinethe bandwidth.The fractional bandwidth of the third-order SIW filter is 13.5% newlinewith a centre frequency of 6.18 GHz. The second SIW wideband BPF is constructed by newlinecombining a perturbing element, and two stepped resonators (R1,R2) on either side of newlinethe perturbing element into a square SIW cavity for a third-order passband operation. newlineThe perturbing element loaded SIW cavity causes different electric field distribution for newlinetwo modes (TE110, TE120) compared to unloaded SIW cavity modes. The mode shifting newlineof the SIW cavity loaded with and without perturbing elements is explained using eigenmode newlineanalysis. Next, the (TE110 and TE120) mode of SIW cavity loaded with perturbing newlineelement is coupled using the two stepped resonators inside the cavity. The coexistence newlineof electric and magnetic coupling between the resonators (R1,R2) and the central perturbing newlineelement produces three poles that improve the proposed filter s bandwidth. The generation of three transmission zeros improves the selectivity of the filter to a greater extent.