This paper outlines the design and development of a cross-coupled bandpass filter with operational frequency at 1.2 GHz, intended for mobile communication applications. To enhance computational efficiency, the filter is decomposed into individual components and each part is simulated separately using HFSS simulator and AWR software, which facilitates the extraction of critical parameters in accordance with a general coupling matrix (CM). A Rogers RO4003C substrate with a thickness of 0.813 mm and dielectric properties of εr = 2.2 and tanϕ = 0.0027 was used in the simulation. The dimensions of the fabricated cross-coupled filter are as follows 25 × 52 × 0.847 mm3, where the filter shows a desirable frequency response with two transmission-limiting zeros as expected. The simulated cross-coupled filter has an excellent electromagnetic performance, it exhibits an insertion loss of 1.1 dB and a return loss of –25 dB within a frequency range of 1.13 GHz to 1.28 GHz. The results show that the analysis, simulation and measurements agree well with each other, proving the accuracy and efficiency of the filter design.

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 of ɛ _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 mm ³ 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.