A compact VHF antenna for smart meters

Energy companies have demanded two way communications between the consumer energy meter and the company to ease data collection and enable variable energy tariffs. There are serval bands in use from GSM to ISM bands working at 900, 315, 434 and 868 MHz. In hilly terrains and meters located in basements these frequencies do not propagate well in these bands, however frequencies below 200 MHz are much better. This work describes a narrow band antenna derived from a perturbed microstrip patch working at 169 MHz. Its largest dimension is only 0.07λ at resonant frequency with a ka = 0.18. A gain of -1.2 dBi and an SII of -2 dB was achieved. The antenna was designed to fit directly to the smart meter so its radiation pattern was optimised to radiate broadside. It incorporates a novel matching element to allow ease of manufacture. From near field studies it can be described as parasitic resonator excited by a single driven electrode matching 50 ohms. The main method of tuning was by altering the separation of the top fin structures. The antenna was finally tuned to the required resonant frequency when enclosed in an polycarbonate plastic housing.