Small Split-Ring Resonators as Efficient Antennas for Remote LoRa IOT Systems—A Path to Reduce Physical Interference

Abstract

While wireless IOT modules can be made extremely compact, antennas typically protrude from the module, providing the potential to catch near moving/rotating equipment or transfer loads to the PCB through end forces, which can lead to failures. This work explores the use of split-ring resonator (SRR) designs to achieve a planar antenna with a maximum dimension less than a monopole working at the same frequency. The very narrow bandwidth of the SRR required detailed physical models to create printed circuit board (PCB)-based antenna designs that could be used at LoRa frequencies of 433 MHz and 915 MHz. Uncertainty analysis allowed for the impact of geometrical and physical tolerances on the resonant frequency to be evaluated. Nearfield and farfield measurements were performed allowing for the resonant frequency, directionality, and range of the antenna to be evaluated. An unbalanced SMA port was added to the SRR design to allow for the use of a network vector analyser to determine the input impedance of various designs. The optimum design achieved an input resistance of 44 Ω at a resonant frequency of 919 MHz, close to the target values (50 Ω at 915 MHz). Field measurements of the received signal strength from a planar antenna design indicated a gain of 5 dB over a conventional quarter-wave monopole antenna, in a footprint that was 40% smaller than the monopole.

New Elliptical Miniaturized Antenna Using Concentric Open Rings for UWB Applications

“…The design presented in this paper combines selected conventional techniques to meet the requirements of a practical UWB system, along with the use of elliptical concentric open rings (CORs). These latter are adopted as an alternative to split ring resonators (SRRs) that suffer from narrow bandwidth operation [48,49]. The procedure introduces elliptical CORs on the patch resulting in a multitude of current paths.…”

A Novel Strategy for Monitoring a PV Junction Box Based on LoRa in a 3 kW Residential PV System

“…On the contrary, since it has a very low data transfer rate of less than 100 bps, there are restrictions in monitoring the PV junction box in the case of a large-scale PV system or a large amount of processed data. LoRa is a representative technology of low-power long-distance communication and provides a very wide communication range with low power [25][26][27][28]. In an open area, LoRa gives a wide coverage of over 10 km in perfect conditions and consumes 10 mW at most [29].…”