Miniaturized Ultra-Wideband Omnidirectional Whip Antenna with Improved Gain

This paper introduces a novel miniaturized ultra-wideband omnidirectional whip antenna with enhanced gain performance. The antenna is fed by a tapered coplanar waveguide (CPW), and its radiating element is modeled after a double-ridged horn antenna. To improve the impedance matching at low frequencies, distributed resistors are loaded at the end of the patch. Through electric field distribution analysis, two pairs of parasitic elliptical patches and slots are strategically added to the back of the antenna, significantly improving gain at higher frequencies. The antenna achieves dual-band operation, with 131.6% (0.68-3. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3\text{GHz})$</tex> ultra-wideband at the low frequency and more than 22.2% (4.8-6GHz) bandwidth at the high frequency. The radiation pattern demonstrates excellent horizontal omnidirectional characteristics, with minimal 3dB gain fluctuation across the effective frequency band. Additionally, the overall size of the antenna is only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.06 \lambda_{\text{low }} \times 0.25 \lambda_{\text{low }} \times 0.001 \lambda_{\text{low }}$</tex>, which makes it well-suited for mobile communications, satellite communication, Internet of Things (IoT) and so on.