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

Abstract

This paper presents a novel passive Schottky-diode frequency doubler equipped with an on-off keying (OOK) modulation port to be used in harmonic transponders for both identification and sensing applications. The amplitude modulation of the second-harmonic output signal is achieved by driving a low-frequency MOSFET, which modifies the dc impedance termination of the doubler. Since the modulation signal is applied to the gate port of the transistor, no static current is drained. A proof-of-concept prototype was manufactured and tested, operating at 1.04 GHz. An on/off ratio of 23 dB was observed in the conversion loss of the doubler for an available input power of −10 dBm. The modulation port of the circuit was excited with a square wave (fm up to 15 MHz), and the measured sidebands in the spectrum featured a good agreement with the theory. Then, the doubler was connected to a harmonic antenna system and tested in a wireless experiment for fm up to 1 MHz, showing an excellent performance. Finally, an experiment was conducted where the output signal of the doubler was modulated by a reed switch used to measure the rotational speed of an electrical motor. This work opens the door to a new class of frequency doublers, suitable for ultra low-power harmonic transponders for identification and sensing applications.

Biomaterial Inks from Peptide-Functionalized Silk Fibers for 3D Printing of Futuristic Wound-Healing and Sensing Materials

“…The circuit, demonstrated in ref. [ 28 ], is a passive frequency doubler, based on a series-connected low-barrier Schottky diode and two quarter-wave stubs working as harmonic filters [ 29 ]. Input- and output-matching networks were added to match the circuit to input and output impedances of 50 Ω.…”

“…When the applied pressure is below threshold, the two copper plates are separated, and no DC current can flow in the circuit. This modifies the self-bias point of the diode [ 29 ], thereby increasing the doubler’s frequency conversion loss or, equivalently, reducing the power of the second harmonic signal at the output port. A bypass capacitor (C b ) is connected in parallel with the 3D-printed grid shock sensor, to avoid the RF signals being affected by the sensor parasitics.…”

Microwave-Enabled Wearables: Underpinning Technologies, Integration Platforms, and Next-Generation Roadmap

“…The piezoresistor is inserted at the output matching network of the frequency doubler and controls the level of the DC voltage which make the sensor reverse biased, thereby varying the magnitude of the backscattered second harmonic [115]. Similarly, the matching network could be loaded using a switch driven by an encoded bit-stream [116], enabling the harmonic modulator to carry more information in a clutter-free, dual-band, and bi-static manner, which could be particularly attractive for fully-integrated transponders, e.g. Fig.…”

Passive Harmonic Vibration Sensor based on Amplitude Modulation for Industrial Application

“…An NMOS transistor is used to control the self-bias point of the Schottky diode (Vdc in Fig. 1), thereby causing the amplitude modulation of the generated second harmonic signal [3]. A piezoelectric cantilever is connected to the gate of the transistor [4].…”

“…1), thereby causing the amplitude modulation of the generated second harmonic signal [3]. A piezoelectric cantilever is connected to the gate of the transistor [4]. This way, when a vibration occurs, a sinusoidal signal vgs is developed, and the transistor is periodically switched from off to triode region.…”