Frequency Agile Omnidirectional Alford Loop: an Implementation Perspective Overview

A compact circular Alford Loop antenna design is proposed to work at 400 MHz and 440 MHz UHF bands for satellite-based IoT applications. The frequency reconfiguration mechanism is based on PIN -diode switching. The design of a matching circuit to allow the diodes DC bias over the RF structure is presented, with a focus on practical discrete surface mounted components. Measured results on a prototype of the antenna agree with simulations, confirming the horizontal polarization and frequency switch by simply applying a DC bias over the antenna's SMA connector. The compactness and radiation characteristics of this antenna make it a good candidate for new generation of low-cost IoT satellite-based communication's ground station.