Effect of the openings in a compact patch antenna for an RFID-sensor-node

Wireless sensing with UHF RFID tags gets attention in the last years. Some systems integrate sensor components on the tag beside the RFID chip. For this application type a patch antenna that integrates sensor components and the RFID chip in openings in the top and the bottom patch has been developed. The antenna is presented and an analysis of the size and the placing of the openings to the gain and the input impedance is shown.