High‐gain horizontally polarised omnidirectional planar antenna using parasitic directors for wireless sensor networks

Abstract

SummaryWireless sensor networks (WSNs) are used to monitor the real‐time parameters of remote/restricted access areas of automation industries which are tightly sealed. In such scenarios, the main challenge is signal transmission in sealed environments. An omnidirectional radiation pattern is preferred as a control link for receiving packets or periodic updates from its neighbouring nodes. However, the gain and directivity of omnidirectional antenna should be sufficient enough to transfer the data to the collecting node. This paper proposes a high‐gain horizontally polarised omnidirectional radiation pattern planar antenna resonating at the 2.45 GHz. The developed microstrip planar antenna offers a very simple and compact structure printed on either side of FR4 epoxy substrate (ε = 4.4) suitable for WSN nodes. A printed dipole director is arranged orthogonally and offers horizontal polarisation. A pair of parasitic elements is placed parallel to dipole radiators to improve the total gain of the antenna. A parallel pair of parasitic elements is placed on an inclination of 45° in antenna design plane for uniform distribution of surface current to achieve the omnidirectional antenna. The symmetrical structure of the radiating element on either side of the substrate avoids the design of the traditional balun structure to reduce the complexity of feeding network. The developed antenna is simulated, fabricated, measured and tested using WSN. The measured radiation (directivity = 3.9 dBi) is maximum at Ⴔ = 0° and Ⴔ = 90°. The frequency response of the antenna indicates a −10 dB fractional bandwidth of 380 MHz (2.24 GHz–2.62 GHz). The measured far‐field response shows a stable average gain of 3.9 dBi over the ISM band. The real‐time received signal strength indicator (RSSI) of the antenna installed in the sensor node observed a success rate of 79.46% with a transmission error of 10%. The observed response of an antenna makes it well‐suitable for WSN in industrial automation.