Rectangular Shaped Quarter Mode Substrate Integrated Waveguide (R-QMSIW) 1 x 2 MIMO Antenna for Sub-6 GHz and WiMAX Applications

Introduction: In this work, a compact rectangular-shaped Quater-mode Substrate Integrated Waveguide (R-QMSIW) 1 × 2 MIMO antenna with a defective rectangular slot loading is demonstrated for sub-6 GHz and WiMAX applications. The suggested antenna is implemented on an FR-4 substrate material (εr = 4.3) to achieve miniaturization and dual-band operation. CST software was used for simulation, and experimental validation was carried out to assess its performance. Method: The Substrate-Integrated Waveguide (SIW) is predominantly regarded as the preferred medium for transmission in high-frequency applications. The dual-band performance was observed by loading the antenna with a defective rectangular slot on its top patch and a rectangular slot on the bottom ground plane. Results: The proposed antenna resonates at 3.5 GHz and 4.93 GHz, achieving measured gains of 3.37 dBi and 4.28 dBi, respectively. MIMO parameters exhibit isolation less than –20 dB, an Envelope Correlation Coefficient (ECC) below 0.001, Channel Capacity Loss (CCL) under 0.1 bits/sec/Hz, and Total Active Reflection Coefficient (TARC) less than –15 dB. A Diversity Gain (DG) greater than 9.9975 dB confirms its suitability for wireless standards. Discussion: The use of defective rectangular and rectangular slots enhances impedance matching and radiation performance while maintaining a compact size. A strong correlation is observed be tween simulation and fabricated-prototype results, validated using a Vector Network Analyzer (V NA). Across the operational bands, the suggested antenna shows stable radiation properties. Conclusion: The demonstrated R-QMSIW 1 × 2 MIMO antenna exhibits excellent dual-band performance, high gain, and desirable diversity characteristics. These results confirm its suitability for deployment in modern 5G telecommunication systems and WiMAX applications.