Design of helical antenna for SAW passive wireless temperature sensor

A sensor antenna which is suitable for using as SAW passive wireless temperature measuring system has been designed based on the basic theory of the helical antenna in this paper. The size of the helical antenna has been identified. Firstly the modeling and optimization of the helical antenna have been carried out by using the HFSS software, thus the final dimension of the helical antenna with 433MHz resonant frequency and 300~500 MHz broadband has been determined. Then a impendence matching network between the antenna and the sensor has been designed by using the ADS software, which makes their input impendence conjugate. The simulation results are in good agreement with the measured ones. The voltage standing wave ratio (VSWR) of the antenna is less than 1.2 over the whole frequency range. Finally the sensor is wireless tested combining with the reader, showing the practicability of the sensor.