Design of a quasi-chipless harmonic radar sensor for ambient temperature sensing

Abstract

This paper presents a passive wireless tag for ambient temperature sensing. The tag uses harmonic radio-frequency backscattering to encode and transmit the measured value. The harmonic radar approach is taken due to the advantage of a radar clutter-free Rx signal, which increases the applicability of the tag significantly compared to many other chipless sensors. The harmonic tag is fabricated with planar printed circuit board technology and it uses a harmonic generator based on a single unbiased diode. The tag setup and wireless proof-of-concept measurements with a range of more than 3.25 m are presented.Index Terms-Passive microwave remote sensing, temperature sensors, sensor systems and applications, radio frequency.

Harmonic Synthetic Aperture Radar Processing

“…If a fixed unambiguous range is required, and the second harmonic is investigated, the sampling frequency of the beat signal must be doubled as compared with the conventional case. Accordingly, if harmonics up to order L is investigated, the sampling frequency must be increased by a factor L. We note that, after low-pass filtering the result indicated in (11), the overall result is the same as if a conventional FMCW system had been applied to a single harmonic signal within the frequency band [2f 0 , 2(f 0 + B)]. This means that the different harmonic components of the return signal is separated in the receiver.…”

“…Harmonic radar has also been used to track insects and small animals [3]- [7]. Other known applications are, for example, in problems related to detection of vital signs [8]- [10], temperature sensing [11], [12] and detection of radio-frequency (RF) electronics [13]. Many of the applications for harmonic radar rely on using tags that cause higher order harmonic reflections when illuminated by an RF signal.…”

A chip-less and battery-less subharmonic tag for wireless sensing with parametrically enhanced sensitivity and dynamic range

“…The interrogation frequency, temperature range, communication range and EIRP relative to the reported SubHT are compared to those of other previously developed counterparts tested in uncontrolled (this work and Refs. [45][46][47][48][49][50] or controlled (Ref. 51 ) electromagnetic scenarios.…”

Energy-Efficient Harmonic Transponder Based on On-Off Keying Modulation for Both Identification and Sensing

“…So, they can be placed in harsh environments and in remote areas. These features justify their application for insect-tracking [7][8][9], condition monitoring [10][11][12][13], and search-and-rescue applications [14,15].…”

“…Some attempts to encode additional information in harmonic tags have been already reported in the literature. Most harmonic transponders encode sensor information statically in the power of the back-scattered second harmonic [11,12]. However, the received power also depends on the channel and on the tag-to-reader distance, which makes information recovery prone to errors.…”