Multi-Band Ring Microstrip Patch Antenna Enhanced by Nd: YAG Laser Processing at C-band for Wireless Communications

This paper presents the design, fabrication, and experimental characterization of slotless and slotted ring microstrip antennas implemented on an FR-4 substrate and subsequently modified through Nd: YAG laser treatment. The experimental investigations reveal significant improvements in impedance matching, bandwidth, and multi-band performance as a result of the combined influence of slot incorporation and laser-based modification. For the slotless configuration, the antenna response transitions from a conventional dual-band to a more versatile multi-band behavior, supporting five distinct resonances in the frequency range from 3.89 to 7.64 GHz. Among these, the resonance at 5.12 GHz demonstrates the most favorable performance with a reflection coefficient of –23.13 dB, a voltage standing wave ratio (VSWR) of 1.15, and an effective bandwidth of 130 MHz. Similarly, the slotted variant exhibits five resonances between 4.04 and 7.73 GHz, with excellent impedance matching at 5.15 GHz (S11 = –21.7 dB, VSWR = 1.18) and a broader bandwidth of 180 MHz, alongside additional operational modes at higher frequencies. These results confirm that slot loading, in synergy with laser surface modification, effectively enhances the electromagnetic characteristics of the antennas. Consequently, the proposed designs demonstrate strong potential for deployment in modern wireless communication systems, including Wi-Fi, Bluetooth, WLAN, and emerging 5G applications.