UWB loop antenna with stable broadside radiation characteristics

Abstract

ABSTRACTIn this article, a circular loop antenna with stable broadside radiation characteristics for ultrawideband (UWB) applications is proposed. It consists of a circular loop and circular sectors, and the circular sectors are used to directly match a 50‐Ω feed line over a UWB frequency band. The geometry of the proposed antenna is optimized to cover the 3.1–10.6 GHz UWB frequency band with stable broadside radiation patterns. The input impedance and voltage standing wave ratio (VSWR) characteristics of three different structures (a center‐fed circular loop with thin strips, a structure with circular sectors as an end‐truncated semicircular dipole, and the proposed loop antenna with circular sectors) are compared. The optimized proposed antenna is fabricated on a Teflon substrate. It exhibits a measured impedance frequency band of 3.08–12.27 GHz (120%) for a VSWR < 2, which ensures operation in the UWB band. Measured broadside gain is 3.0–7.0 dBi, and stable broadside radiation patterns are observed in the entire UWB band. Measured group delay remains almost constant with a variation of less than ±0.5 ns for the face‐to‐face orientation, and this indicates good time domain performance of the antenna. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2515–2519, 2015