Wireless CSRR based sensing system for Sensitivity Evaluation of Dielectric Materials in Nearfield ISM-Band

Abstract

RF sources required for exciting RF planar sensors are usually supplied through VNA which makes the detection procedure very cumbersome and introduces limitations in portability. In this paper, a wireless sensing system is proposed in which a RF planar sensor at 2.45 GHz is excited with the help of a Voltage Controlled Oscillator(VCO) designed in the range of 2.1GHz to 2.46 GHz having maximum power output of 1.7dBm at 2.4 GHz. The VCO prototype is designed in Altium software and fabricated on FR4 substrate using IC HMC385 LP4 and connected with a pair of transmitting and receiving broadband standard RF antenna arrangement in the frequency range 2.1-3.1GHz. The modified CSRR structure is designed on Taconic substrate with a fractional sensitivity of 8.16 % with a Q of 123. The VCO model, sensor, antenna and Spectrum Analyzer integration is carried out in ADS together to demonstrate the proposed prototype. The integrated antenna system is then simulated in small distances and the change in sensitivity and quality factor is reported. An equivalent structure for the sensor structure is modelled in ADS and its lumped elements are optimized. Finally, the detection is determined by using a Spectrum analyzer modelling and noting the power level of the harmonics undergoing a shift due to the loading of the sample.