Depolarization in three dimensions: Theoretical formulations and empirical results

Golmohamadi, Marcia; Frolík, Jeff

doi:10.1109/wamicon.2016.7483834

Cited by 10 publications

(3 citation statements)

References 16 publications

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“…The antenna is a key component in RFTacho's hardware as it is responsible for emitting and receiving the electromagnetic waves. However, linear antennas suffer from severe depolarization in industrial environments [13,15]. Depolarization means that an obstacle alters the polarization of the incident electromagnetic wave by a certain percentage.…”

Section: Antenna Comparisonmentioning

confidence: 99%

“…The TX and RX antennas are co-located inside the same device, allowing for a small form-factor that can be easily deployed in industries. OAM antennas have two advantages: 1) higher immunity against depolarization in high scattering environment [15], 2) OAM waves interact with the rotational motion by changing its frequency through rotational Doppler shift, which can be exploited to measure a machine's rotation speed.…”

Section: System Overviewmentioning

confidence: 99%

“…2.3): RFTacho needs to operate in industrial scenarios, where radio waves undergo high scattering from heavy metallic machinery, that change the polarization of the transmitted electromagnetic fields [13]. In these environments, linearly polarized antennas (commonly used in communication systems) suffer from severe depolarization that makes it challenging to identify the signal from noise [15]. Depolarization further reduces the received signal power, leading to a significant decrease in the signal-to-noise ratio.…”

Section: Introductionmentioning

confidence: 99%

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RFTacho: Non-intrusive RF monitoring of rotating machines

Heggo¹,

Bhatia²,

McCann³

2022

Preprint

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Measuring rotation speed is essential to many engineering applications; it elicits faults undetectable by vibration monitoring alone and enhances the vibration signal analysis of rotating machines. Optical, magnetic or mechanical Tachometers are currently state-ofart. Their limitations are they require line-of-sight, direct access to the rotating object. This paper proposes RFTacho, a rotation speed measurement system that leverages novel hardware and signal processing algorithms to produce highly accurate readings conveniently. RFTacho uses RF Orbital Angular Momentum (OAM) waves to measure rotation speed of multiple machines simultaneously with no requirements from the machine's properties. OAM antennas allow it to operate in high-scattering environments, commonly found in industries, as they are resilient to de-polarization compared to linearly polarized antennas. RFTacho achieves this by using two novel signal processing algorithms to extract the rotation speed of several rotating objects simultaneously amidst noise arising from high-scattering environments, non-line-of-sight scenarios and dynamic environmental conditions with a resolution of 1𝑟𝑝𝑚. We test RFTacho on several real-world machines like fans, motors, air conditioners. Results show that RFTacho has avg. error of < 0.5% compared to ground truth. We demonstrate RFTacho's simultaneous multiple-object measurement capability that other tachometers do not have. Initial experiments show that RFTacho can measure speeds as high as 7000 rpm (theoretically 60000 rpm) with high resiliency at different coverage distances and orientation angles, requiring only 150 mW transmit power while operating in the 5 GHz license-exempt band. RFTacho is the first RF-based sensing system that combines OAM waves and novel processing approaches to measure the rotation speed of multiple machines simultaneously in a non-intrusive way.

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Section: Antenna Comparisonmentioning

confidence: 99%

Section: System Overviewmentioning

confidence: 99%