Abstract
A chipless, wireless current sensor system was developed using a giant magnetoimpedance (GMI) magnetic sensor and one-port surface acoustic wave (SAW) reflective delay line for real-time power monitoring in a current-carrying conductor. The GMI sensor has a high-quality crystalline structure in each layer, which contributes to a high sensitivity and good linearity in a magnetic field of 3–16 Oe. A 400 MHz RF energy generated from the interdigital transducer (IDT)-type reflector on the one-port SAW delay line was used as an activation source for the GMI magnetic sensor. The one-port SAW delay line replaces the presently existing transceiver system, which is composed of thousands of transistors, thus enabling chipless and wireless operation. We confirmed a large variation in the amplitude of the SAW reflection peak with a change in the impedance of the GMI sensor caused by the current flow through the conductor. Good linearity and sensitivity of ~0.691 dB/A were observed for currents in the range 1–12 A. Coupling of Mode (COM) modeling and impedance matching analysis were also performed to predict the device performance in advance and these were compared with the experimental results.
Highlights
In modern electrical technologies, there is a need for a system that monitors the real-time power usage at any location and transmits the information wirelessly to a portable reader[1,2]
Wireless current sensing system that comprises of a giant magnetoimpedance (GMI) magnetic sensor and one-port surface acoustic wave (SAW) delay line
The one-port SAW reflective delay line consists of input interdigital transducer (IDT) connected to an antenna, a shorted-grating reflector for a reference peak, and an IDT-type reflector linked to the GMI sensor
Summary
There is a need for a system that monitors the real-time power usage at any location and transmits the information wirelessly to a portable reader[1,2]. Current sensors based on GMI and giant magnetoresistance (GMR) have been reported in literature, and are preferred because of their high sensitivity, wide frequency range, small size, low power consumption, and facile compatibility with CMOS technologies[20,21,22,23,24,25]. The development of this kind of current sensors has been facilitated by the progress in both theoretical and technological methods. Karilainen et al developed the voltage sensor for biomedical application based on a SAW delay line with voltage-dependent impedance loading on a reflector IDT35
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