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Abstract Optical frequency combs, featuring evenly spaced spectral lines, have been extensively studied and applied to metrology, signal processing, and sensing. Recently, frequency comb generation has been also extended to MHz frequencies by harnessing nonlinearities in microelectromechanical membranes. However, the generation of frequency combs at radio frequencies (RF) has been less explored, together with their potential application in wireless technologies. In this work, we demonstrate an RF system able to wirelessly and passively generate frequency combs. This circuit, which we name quasi-harmonic tag (qHT), offers a battery-free solution for far-field ranging of unmanned vehicles (UVs) in GPS-denied settings, and it enables a strong immunity to multipath interference, providing better accuracy than other RF approaches to far-field ranging. Here, we discuss the principle of operation, design, implementation, and performance of qHTs used to remotely measure the azimuthal distance of a UV flying in an uncontrolled electromagnetic environment. We show that qHTs can wirelessly generate frequency combs with μWatt-levels of incident power by leveraging the nonlinear interaction between an RF parametric oscillator and a high quality factor piezoelectric microacoustic resonator. Our technique for frequency comb generation opens new avenues for a wide range of RF applications beyond ranging, including timing, computing and sensing.
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This content will become publicly available on December 2, 2026
A Batteryless Wireless Microphone Using RF Backscatter
Wireless microphones are essential tools in business, education, entertainment, and other domains. However, most existing designs rely on batteries, leading to the inconvenience of frequent recharging and the risk of unexpected power failure during use. In this paper, we present TagMic, a battery-free wireless microphone enabled by a novel radio frequency (RF) backscatter technology. TagMic is built on two key innovations.(i) Parametric backscatter tag design:This design enables the RF tag to operate at separate excitation and reflection frequencies, fundamentally mitigating the self-interference problem inherent in conventional RFID systems. Unlike harmonic backscatter approaches, it also requires a significantly lower activation voltage, resulting in a longer communication range.(ii) Voice modulation via RF coupling:A passive piezoelectric sensor is integrated with the RF tag through RF coupling to enable analog-domain frequency modulation (FM), directly encoding voice signals onto the backscattered signal. This eliminates the need for digital signal processing, allowing for truly continuous voice streaming. We have built a prototype of TagMic and evaluated it under realistic conditions. Extensive experiments demonstrate its effectiveness in achieving battery-free, continuous, and seamless wireless voice streaming in realistic applications.
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- Award ID(s):
- 2225337
- PAR ID:
- 10656467
- Publisher / Repository:
- ACM
- Date Published:
- Journal Name:
- Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies
- Volume:
- 9
- Issue:
- 4
- ISSN:
- 2474-9567
- Page Range / eLocation ID:
- 1 to 18
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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