EM Design, Realization and Measurement of a Hexagonal SIW-Based Bandpass Filter for Wireless Communication

Abstract

This paper presents a new design for a third-order bandpass hexagonal substrate integrated waveguide-defected ground structure
(SIW-DGS) filter for mobile communications applications. The proposed design operates at 7.90 GHz. It combines the flexibility of
rectangular cavities and the efficiency of circular cavities to enhance the filter’s electromagnetic (EM) performance and selectivity. To facilitate the filter analysis and improve its computational efficiency, the developed structure is decomposed into individual components and simulated separately using high frequency structure simulator (HFSS) and applied wave research (AWR) software that help extracting critical parameters based on a general coupling matrix (CM) using RT/Rogers 4003 substrate with a dielectric constant ε_r = 3.55, tan δ = 0.0027 and a thickness of 0.508 mm. The simulated EM filter response shows an insertion loss of up to 1.58 dB and a return loss of less than −23.5 dB over the operating frequency range from 7.77 GHz to 8.05 GHz, demonstrating a high EM performance. Accordingly, an efficient third-order bandpass hexagonal SIW-DGS filter prototype of a 17 × 22.9 × 0.542 mm³ volume is realized and demonstrates an accurate EM response with a defined zero transmission, as expected. Measured results of the optimized third-order bandpass hexagonal SIW-DGS filter with a trisection cross-coupled structure and a fractional bandwidth (FBW) of 3.54 % show high agreement with the calculated and simulated results, which validates the efficiency of the developed design as a highly accurate candidate for modern communication systems requiring compact structures.