Study Of The Sensors Based On Chipless RFID And The Reader Antenna

With the development of internet of things,the sensors based on RFID technology are put more and more attention.As the main components used to transfer the information,and the performance of antenna is also concern widely.In this article,we mainly studied a RFID sensor and a reader antenna.(1)A novel resistance type sensor based on chipless RFID is presented.The used substrate is Rogers R04003 with a relative permittivity of 3.55,size of 48 × 25 × 0.8 mm3.The scatterer is designed to be V-shaped.The fixed arm A is placed along the x-axis and the rotating arm B has an angle ?with respect to x-axis.The angle ? between two arms is used to encode the address data of sensor.The resistor is loaded in the middle of the two V-shaped arms.The sensor is excited by the plane wave.The angle ? and the value of resistor can be identified by measuring the scattered field in two orthogonal polarization directions.The realized sensor has the identification errors less than 3° in the angle and less than 1.5 ? in the resistance value.Every element can carry 4 bits of coding information.Also,for different codes of one element,the proposed sensor uses the same spectrum.This is beneficial to improve the efficiency of the spectrum.(2)A resistance sensor with two unit is studied.The sensor includes two V-shaped radiating patch which was composed of different lengths and angles.The unknown resistance R on one of the unit.The angle ?1 and ?2 between V-shaped radiating patch is used to encode the address data.The results indiate,the realized sensor can encode 5 bit and the identification errors less than 2 ? in the resistance value.(3)A tri-band monopole antenna fed by a coplanar waveguide(CPW)for reader applications is proposed.The realized antenna has a total size of 59 mm×40.55 mm×1.6 mm.The used substrate is FR4.It comprises two different monopoles and can operate at three resonant frequencies of 1.57 GHz,2.4 GHz and 3.5 GHz.The frequency 1.57 GHz and 3.5 GHz are controlled mainly by the longer monopole and 2.4 GHz is mainly decided by the shorter monopole.In order to improve the gain of the antenna,a rectangular patch is added on the left side of the ground plane.The measured results show that the bandwidth at three frequencies are 254 MHz(1.518-1.772 GHz),461 MHz(2.289-2.75 GHz)and 226 MHz(3.514-3.714 GHz)respectively,covering the band for GPS,WLAN and wireless access system.The gain are 2.15 dBi,3.12 dBi and 3.86 dBi respectively.