A wireless chipless temperature sensor utilizing an orthogonal polarized backscatter scheme

A novel passive wireless temperature sensor is presented which is designed planar and chipless. The sensor tag uses a backscatter scheme with two linear polarization planes to seperate transmit and receive path during wireless readout. The measured value is encoded in the spectral signature of the tag by a temperature-dependent notch filter. This filter is set up as a coupled line resonator, loaded by an interdigital Barium-Strontium-Titanate (BST) varactor. The temperature-dependency of the permittivity of the ferroelectric BST affects the varactor's capacity and consequently allows a temperature measurement. The sensor has been successfully operated in the temperature range between 20 °C and 85 °C.