Broadband Compact Quasi Yagi Antenna for UHF Wireless Communication Systems with Enhanced Performance at UHF ISM Bands

Abstract

In this study a broadband planar quasi Yagi antenna operated at ultra-high frequency (UHF) band is presented. The performance of the antenna is particularly improved for two popular UHF frequencies of 433 and 868 MHz used in several wireless communication applications such as Long Range (LoRa) Internet of Things (IoT) Machine-to-Machine (M2M) Wireless Meter bus (M-bus) and Radio Frequency Identification (RFID). The proposed antenna includes a printed feed dipole with a ground reflector and two parasitic (director) elements on a substrate to keep total dimensions of the antenna within compact size. The parasitic elements are very thick and closely spaced to feed dipole. Significant increase in the bandwidth is obtained with the improved effects due to usage of tapered feed line and tapered reflector. The antenna's 10-dB return loss bandwidth is measured more than 70% between 428 MHz and 896 MHz. The antenna offers moderate peak gain values of 5.5 dBi and 5 dBi, and front-to-back ratio (F/B) values of 12 dB and 14 dB at lower and higher parts of UHF band around 433 and 868 MHz respectively. The peak gain and F/B ratio values are found to be minimum 4 dBi and 8.5 dB within the operating bandwidth respectively.