Omnidirectional to Directional Pattern Switching Patch Antenna for Wireless Sensor Nodes at Nuclear Reactor Containment Building

Abstract

The novel design, prototyping, and characterization of an omnidirectional to directional radiation pattern switching planar antenna system are presented. The incorporation of the Yagi-Uda antenna with an Alford loop antenna is proposed. The antenna is formed by a dipole, driver, reflector, and two directors. In a DC bias switching circuit with a combination of eight SMD PIN diodes and two parasitic elements, the antenna's radiation patterns can be shaped to concentrate energy in an omnidirectional radiation pattern. The introduction of switches using an SMD PIN diode at the arms of the driver element produces two switchable frequencies at 915 MHz and 2.45 GHz. Switches at the directors and reflector control the radiation pattern and can be configured to omnidirectional pattern to directional radiation pattern at those resonance frequencies. The radiation patterns as well as the simulated and measured reflection coefficients (S₁₁) are illustrated and analyzed. Return loss (S₁₁) is observed to be −36.36 dB at resonance frequency of 2.45 GHz (2.35–2.69 GHz) with bandwidth 340 MHz and impedance bandwidth 21.1%, and −24.45 dB at resonance frequency of 915 MHz (854–1006 MHz) with bandwidth 152 MHz and impedance bandwidth 16.61%. When compared with the omnidirectional pattern while maintaining the horizontal polarization, the gain of the antenna increases from 4.6 dBi with 90.02% efficiency to 5.1 dB with 87.77% efficiency in a directional pattern. The developed antenna system's final dimensions are 2.45 λ × 1.80 λ × 0.01 λ. The antenna system is tested in a nuclear reactor containment building equipped with a wireless sensor node. The signal transmission indicates the zero (0) invalid frames with 100 dBm received signal strength indication (RSSI). The printable nature of the antenna architecture and successful transmission of signals across the nuclear reactor containment building make the antenna a good candidate for the wireless sensor node (WSN) in the nuclear reactor.