Impact of Defected Ground Structures on Microstrip Bandpass Filters for 5G/6G Applications

This study presents the design and comparative analysis of microstrip bandpass filters employing intact and defected ground structures (DGS) for operation at 8 GHz, 10 GHz, and 12 GHz. A scale-and-tune methodology was applied to a square resonator topology, combining electromagnetic optimization in ANSYS HFSS with experimental calibration using a vector network analyzer. Prototypes were fabricated on FR-4, RT/Duroid 5880, and Rogers RO3210 substrates, each realized in parallel with intact and defected ground planes. Measured results confirmed the simulations, showing that DGS introduces additional transmission zeros, enhances stopband attenuation by up to 30 dB, and improves selectivity with limited insertion loss penalty. Substrate properties were found to significantly influence matching, bandwidth, and quality factor, while maintaining mechanical stability above 12 GHz. The outcomes demonstrate that integrating DGS into microstrip filters provides a cost-effective strategy for miniaturization and performance enhancement, ensuring suitability for compact RF front ends in emerging 5G/6G wireless communication systems.