A High-Efficiency Compact UWB Antenna with Modified Defected Ground Structure for Defense Applications

Abstract

Modern defense communication and radar systems require a compact, wideband, and high-efficiency antennas those are capable of operating across multiple frequency bands. The paper presents the design and realization of a compact semi-circular ultra-wideband (UWB) microstrip antenna with a modified defected ground structure (DGS), consisting of a rectangular notch to enhance impedance bandwidth and radiation characteristics. The proposed antenna simulated in CST studio and also fabricated on FR-4 substrate of size 30 × 15 × 0.8 mm³, providing a lightweight structure suitable for portable defense equipment and also in the radar system. The antenna operates within two broad frequency regions, 2.74-3.37 GHz and 5.62-20.07 GHz, covering portions of the S, C, X, and Ku bands widely used in radar, surveillance, and satellite communication systems. Structural modifications, including chamfered patch edges and a C-shaped slot, collectively improve the surface-current distribution, suppress surface-wave effects, and enhance the impedance bandwidth, resulting in two distinct operating bands of 2.74–3.37 GHz and 5.62–20.07 GHz, with fractional bandwidths of 20.62% and 112.5%, respectively, and a peak gain of 4.4 dB, and maximum simulated total efficiency of approximately 98%. The measured and simulated results show reasonable agreement, validating the antenna’s ultra-wideband behavior and stable radiation performance. Due to its compact size, coverage across portions of multiple microwave bands, and high efficiency, the proposed antenna is a strong candidate for next-generation multi-band defense communication and sensing applications.