A compact low-cost impedance transformer-fed wideband monopole antenna for Wi-MAX N78-band and wireless applications

Abstract

A compact, transformer-fed, miniaturized, wideband (WB) spearhead-shaped monopole antenna is analyzed, investigated, and fabricated using partial ground structure (PGS). The partial ground is used to achieve wide bandwidth, and a quarter-wave impedance transformer is introduced for impedance matching between a 50 Ω microstrip line and 243 Ω spearhead radiating edge. This results in improved reflection coefficient values lower than −10 dB from 3.28 to 3.83 GHz, and thus, wideband performance is achieved. This fractional bandwidth makes the antenna a suitable candidate for 5G applications like LTE (3.2–3.3 GHz) and Sub-6 GHz, 5G N78-band (3.3–3.67 GHz) in India (3.3–3.8 GHz) and in Europe, Wi-MAX department of telecommunication (3.4–3.6 GHz), and IEEE 802.11y-2008 standard in the USA for LAN and MAN (3.65–3.70 GHz). A low-profile antenna with a size of 13 mm × 26 mm × 1.6 mm has been fabricated on a low-cost FR4 substrate. Therefore, a miniaturized antenna results in a total 85.33% area reduction as compared to a conventional circular patch antenna designed at a frequency of 3.5 GHz with acceptable gain and bandwidth. The RLC electrical equivalent circuit model of the proposed antenna is presented at the end. The simulated results are in concord with the measured results. The antenna exhibits a peak gain of 2.92 dBi and an omnidirectional radiation pattern.