From L-shaped planar monopoles to a novel folded antenna with wide bandwidth

Abstract

A novel folded monopole antenna is investigated numerically and experimentally. The proposed antenna comprises a short folded monopole suitably shaped at the base with two vertical grounding probes. This small antenna is shown to have a fractional impedance bandwidth up to 125% (1.6 GHz to 7.5 GHz) for a 10 dB return loss. An interesting compromise between impedance bandwidth and pattern control is found by tuning a double side bevel at the base of the monopole, the position of the feeding point and its distance from the ground plane. Measurements and simulations are in good agreement and show a dramatic improvement in terms of impedance bandwidth compared with planar and L-shaped monopole antennas. Impedance and radiation characteristics make this novel folded monopole antenna a remarkable candidate for indoor applications where the wideband coverage of different systems is required. The working bandwidth covers a large number of wireless communication systems including GSM 1800, Personal Communication System (PCS1900), Universal Mobile Communications System (UMTS), the 2.4 GHz (2400–2484 MHz) and 5.2/5.8 GHz (5185–5350/5725–5875 MHz) bands for WLAN communication, Wireless Local Loop (3.4–3.6 GHz), the US-NII bands and the lower bands allocated to ultra-wideband communications.