Increasing use of smart meters and Internet of Things (IoT) devices will erode limited bandwidth. Lower-frequency bands at 450 MHz are available for smart-metering applications, but lower frequencies imply larger wavelengths and larger antennas; these may not always be compatible with meters and sensors designed to be inconspicuous. To provide a solution, researchers/designers from different organizations in Dublin, Ireland proposed an ingenuous folded meandering monopole antenna capable of receiving signals within the 410-to-470-MHz UHF range. The antenna is printed on low-cost, double-sided FR-4 printed-circuit-board (PCB) material. The antenna is located on the corner of a rectangular ground plane measuring 130 × 70 mm. Feed and short strips are located on the rear side of the antenna with interconnections to the meandering line by means of a slider and a plated viahole.
The compact UHF antenna design was fabricated, tested, and simulated with commercial simulation software. The moveable aluminum via slider, which controls the resonant frequency, allows tuning at any frequency across the frequency range. The antenna design provides a tunable bandwidth of 409.5 to 481.1 MHz, and the slider can be precisely positioned for a desired operating frequency, such as 450 MHz. The antenna was simulated alone and as an installed component of a system, using different orientations of the antenna ground plane in the models. Although there was some shift in center frequency as a result of the change in ground-plane orientation, the omnidirectional antenna provides a stable radiation pattern across its tunable bandwidth with measured efficiency of 21%. See “Folded Meandered Monopole for Emerging Smart Metering and M2M Applications in the Lower UHF Band,” IEEE Antennas & Propagation Magazine, Vol. 58, No. 2 April 2016, p. 60.
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