Optimizing Vivaldi Antenna Performance: Feeding Strategies for Broadband GPR Bandwidth Expansion

This paper presents the design of a Vivaldi antenna with several types of feedlines, namely microstrip, microstrip with curved, and coplanar waveguide, for broadband Ground Penetrating Radar (GPR) applications. The purpose of using multiple types of feedlines is to widen the antenna's bandwidth without compromising other performance aspects such as gain, radiation pattern, and directivity. The antenna consists of a single element with a simple configuration using an FR-4 substrate with a thickness of 1.6 mm and an overall compact size of 90 mm × 90 mm × 1.635 mm. Furthermore, the implementation of these three types of feedlines offers their own advantages. The microstrip feedline provides multi-band bandwidth characteristics with a gain of 9.78 dB. The microstrip with curved feedline achieves a high gain of up to 9.90 dB with a wider bandwidth characteristic. Meanwhile, the coplanar waveguide feedline offers the widest bandwidth in the range of 1.1 GHz to 4.7 GHz, achieving a gain of 9.85 dB and relatively stable directivity across various frequencies.