A Compact Wideband Microstrip Patch Antenna Using a Partial Ground Plane for 28 GHz mmWave Applications

Millimeter-wave (mmWave) communication is a fundamental enabler for next-generation wireless systems due to its capability to support ultra-high data rates and massive network capacity. However, the design of compact antennas operating at mmWave frequencies remains challenging because conventional microstrip patch antennas suffer from inherently narrow impedance bandwidth and limited radiation efficiency. This paper presents a compact wideband microstrip patch antenna operating at the 28-GHz band using a slot-engineered radiating structure combined with a partial ground plane. The antenna is fabricated on a Rogers RT5880 substrate (εr = 2.2, tanδ = 0.0009) with overall dimensions of 20 x 21 x 0.79 mm3. Bandwidth enhancement is achieved by introducing multiple resonant perturbations through strategically positioned slots, which effectively alter surface current distribution and reduce the antenna quality factor. The proposed antenna achieves a – 10 dB impedance bandwidth of 4.88 GHz (26.88-31.76 GHz), specifically covering n257 (26.5-29.5 GHz), n258 (24.25-27.5 GHz), and n261 (27.5-28.35 GHz) bands fully covering the targeted 28-GHz mmWave band. At the resonance frequency, the antenna demonstrates a return loss of – 46.91 dB, VSWR of 1.009, peak gain of 6.45 dB, and radiation efficiency exceeding 92 %. Electromagnetic analysis confirms that the slot configuration generates multiple coupled resonant modes, enabling broadband performance while preserving radiation stability. Comparative analysis with recently reported mmWave antennas demonstrates that the proposed design achieves a favorable trade-off between compact size, bandwidth, and radiation performance. These characteristics make the antenna a strong candidate for 5G, beyond-5G, and emerging 6G millimeter-wave communication systems.