No abstract

No abstract

A novel passive wireless temperature sensor is presented, which aims at operating in harsh environments. For this purpose, the tag is designed quasi-chipless and it uses a harmonic radar sensing principle: it combines the backscattering on the first harmonic of the transmitted frequency with frequency-position encoding of the measured value. The harmonic radar approach brings significant advantages for the wireless readout, since it isolates the undesired radar clutter from the useful tag signal. The tag signal carries the desired temperature information encoded in the position of a resonance transmission peak. The tag is built up planar and consists of two patch antennas, a temperature-dependent bandpass filter and a diode-based harmonic generator. It works at 1.59 GHz and backscatters at 3.18 GHz. Wireless indoor measurements have proven the concept. The sensor has shown a temperature sensitivity of 1.2 MHz/K in the range of 22-109°C.

A passive wireless temperature sensor with identification capabilities based on a phase modulation scheme is discussed in this paper. The approach presented utilizes a pulse backscatter technique based on slow wave (metamaterial) transmission lines. The focus of the work are the material engineering for the temperature-sensitive element and the integration of this element into a passive phase modulation circuit and the entire sensor tag. The approach makes use of temperature-sensitive bariumstrontium-titanate thick film capacitances. The discussed principle has been experimentally verified with a prototype.

This paper introduces three novel passive phase modulators for entirely electromagnetic chipless time domain RFID tags. The modulators overcome limitations of earlier approaches and allow for a highly increased signal space coverage, and, therefore, the implementation of high order PSK or QAM schemes. All three modulators are studied in theory and practically implemented up to a 16-PSK on a reconfigurable prototype tag with 4 modulation stages, realizing a 16 bit information content. Besides showing the measurement results, the assets and drawbacks of the three approaches are carefully compared and the achieved information density is related with approaches from literature.