A Curved Monopole Antenna for HF Radar with Enhanced Gain and Bandwidth

TL;DR

This paper introduces a curved monopole antenna design that enhances gain and bandwidth for HF radar, demonstrating improved performance over conventional antennas through simulation and array extension.

Contribution

The paper presents a novel curved monopole antenna design with optimized curvature and straight sections, achieving significant gain and bandwidth improvements for HF radar applications.

Findings

Achieved 18.5% gain increase and 400 kHz bandwidth expansion.

Demonstrated stable array behavior with 24% gain enhancement.

Provided a compact, broadband antenna solution for next-generation HF radar.

Abstract

This paper presents the design and simulation of a new curved monopole antenna optimized for skywave HF radar applications, with a systematic investigation of the effects of curvature and fixed-section length on antenna performance. The proposed design achieves improved impedance matching, broader bandwidth, and enhanced realized gain compared to a conventional quarter-wavelength monopole at 15 MHz. Parametric analysis shows that fully bending the monopole degrades performance, whereas introducing a straight section and carefully optimizing the curvature enables a 18.5% gain increase and a 400 kHz bandwidth expansion. The single-element design is further extended to a 12-element linear array with 0.45{\lambda} spacing (where {\lambda} is the wavelength), demonstrating stable embedded-element behavior and improved low-to- moderate elevation gain for skywave over-the-horizon radar operation. At {\theta} = 30{\deg}, the proposed array achieves 14.04 dBi compared to 13.11 dBi for the reference array, corresponding to 24% gain enhancement, which is significant in high-power HF radar systems. These results confirm that the proposed curved monopole antenna provides a compact, broadband, and scalable solution for next-generation HF radar arrays.