1. Introduction
IoT devices increasingly need to support both licensed 5G sub-6GHz bands and adjacent unlicensed spectrum from a single compact antenna to minimise board area and bill of materials, motivating dual-band designs that avoid the size penalty of separate single-band elements.
2. Methodology
A rectangular microstrip patch antenna was designed on a 1.6mm FR4 substrate with a defected ground structure comprising two rectangular slots tuned to introduce a second resonance, targeting the 3.5GHz 5G band and the 5.8GHz ISM band on a compact 24mm by 20mm footprint, simulated in HFSS and subsequently fabricated and measured using a vector network analyser and anechoic chamber.
3. Results
The fabricated prototype achieved a measured return loss of -17.2dB at 3.5GHz and -15.8dB at 5.8GHz, with measured peak gains of 4.1dBi and 5.3dBi respectively, and measured E-plane and H-plane radiation patterns tracked simulated patterns within a 1.2dB margin across the tested angular sweep, confirming the defected ground structure achieved its intended dual-resonance behaviour.
4. Conclusion
The defected ground structure approach enables a compact, single-element dual-band antenna suitable for space-constrained 5G IoT devices without a substantial gain penalty relative to single-band designs. Future work will investigate a tri-band extension incorporating the 700MHz sub-1GHz IoT band.
References
[1] Balanis C. A., Antenna Theory: Analysis and Design, Wiley, 2016. [2] Guha D. and Antar Y. M. M., Microstrip and Printed Antennas, Wiley, 2011.