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Vital signs over multiplexed radio by near-field coherent sensing (NCS)

For the first time, NCS was formulated and demonstrated to monitor the vital-sign dynamics of heartbeat, respiration, and blood pressures of people [Hui, Kan, Nat. Electron. 2018] and various animals [Hui, Kan, Sci. Adv. 2019]. NCS modulates vital signs, including the heart rate, respiration rate, breath effort, and blood pressures, onto multiplexed RF signals by wearable sensors without direct skin contact and can monitor multiple people and multiple points of one person with high interference isolation and signal-to-noise ratio.


The human torto electromagnetic mechanical hybrid simulation of near-field coherent sensing (NCS) by CST Microwave Studio.

NCS News

Wireless version NCS system illustration by Nature News.


Radio ranging with ultra-high resolution using a harmonic radio-frequency identification system

An UHF RFID ranging system was demonstrated with the resolutions of 50 μm in air and 5 μm in water at 1 kHz sampling rate [Hui, Kan, Nat. Electron. 2019], which is the highest performance achieved by the UHF system. The system is not limited by the Uncertainty Principle from Fourier transform mathematical model, so the high spatial and temporal resolutions can be achieved simultaneously.

Real-time experiment with 25 μm step measurement in water with 1 kHz refresh rate.


The schematics of the ultra-high resolution harmonic RFID ranging system.

Real-time 3D harmonic tag tracking: single tag free moving, robotic arm, and toy train.

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The schematic of the harmonic RFID 3D localization system.


Multi-channel heartbeat dynamics and single-point noninvasive pulmonary blood pressures (DoD, CDMRP)

A new wearable radio-frequency sensor with multiple observation points can give central systolic and diastolic blood pressures as well as detailed heartbeat dynamics that follow the traces of the Wiggers Diagram.

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The multi-channel heartbeat dynamics sensing system. (a)(b) Sensing antenna pairs. (c) 4-point, 16-channel system by SDRs. (d) Testing on a person. 

Multi-channel NCS signals with ECG and stethoscope


Blood pressures analyses in heart ejection phase functions (middle). Aortic pressures analyses (left). Pulmonary pressures analyses (right).

Heart sound recovered from RF signals comparing with the stethoscope. (please unmute the video)


  • X. Hui and E. C. Kan “Multi-point near-field RF sensing of blood pressures and heartbeat dynamics,” IEEE Access, vol. 8, pp. 89935–89945, 2020.

No-touch measurements of vital signs in small conscious animals

Monitor the vital sign signals without the notice of the animal with UHF band RF system. 

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Schematic of the wireless NCS system

Real-time heartbeat and breath monitoring of a parakeet.


CDMA protocols in Harmonic RFID System

The harmonic RFID system with code division multiple access (CDMA) on tags and readers solved the problems of the conventional systems which limit the read yield rates and real-time multi-tag sensing applications [Hui, Ma, Kan, IEEE J. RFID 2017; Hui, Kan, IEEE J. RFID 2018]. The patents were purchased by Tandem Launch (Montreal, Canada) for $ 800k.

Tag CDMA indoor localization

Harmonic RFID

Harmonic RFID localization system with tag CDMA protocol

Collaborative CDMA reader in harmonic RFID system


Two nearby RFID readers can suffer from reader-to-reader collision (R2RC) for tags within the overlapped reading zone as well as possible reader receiver jamming.


Experimental scenario with various scatters (black blocks) in the reading zone to create complex multi-path.

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The failure rates in the single reader scheme and the collaborative CDMA reader scheme. Slope higher than 2 suggests anticorrelation in individual reader failures and rich reader collaboration.


UHF RFID indoor imaging for tagless persons (on-going, ARPA-E)

The harmonic RFID and conventional RFID system were applied as the multi-static imaging system for the smart building and assistant live applications. The system can obtain the tag-less object’s imaging to derive the location, object shape and dynamic information.


The 1:6 scale model of a conference room with 2 persons inside. The microwave images (3D and 2D) are shown on the screen.

 Personal thermoregulation (Supported by ARPA-E)

Integrate the thermoelectric devices on the undergarments for the personal thermoregulation. The innovative passive garment-integrated temperature sensor is developed and tested.


 The thermoelectric energy conversion unit.

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The RFID based passive temperature sensor is integrated on a conductive embroidered antenna, and the temperature reading is shown on the computer screen (~21 °C).


  •  L. Lou, D. Shou, H. Park, D. Zhao, Y. S. Wu, X. Hui, R. Yang, E. C. Kan and J. Fan “Thermoelectric air conditioning undergarment for personal thermoregulation,” Energy and Buildings, vol. 226, pp. 110374, 2020.

Multiplexed Millimeter Wave Communication with Dual Orbital Angular Momentum (OAM) Mode Antennas

(work before Cornell)

With a customized ring resonator structure antenna, two orbital angular momentum modes millimeter wave (60 GHz band) beam can be generated. The MMW vortex multiplex communication link is achieved and tested.


The explosive view of the dual-mode OAM antenna operating at 60 GHz band.


The CST simulation of the antenna generating the OAM beam of l=+3.

Dual-mode OAM multiplex communication.


Distributed Fiber Optics Sensor (work before Cornell)

A real-time 22 km range, 15 m resolution distributed fiber optics sensor was built and tested with the innovated hardware and algorithm design.


Distributed fiber optics sensor schematic.

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Frequency-distance analyses of the sensor signal.


  • X. Hui, et al. “Hilbert–Huang transform time-frequency analysis phi-OTDR distributed sensor.” IEEE Photonics Technology Letters 26 2403-2406, (2014).

  • X. Hui, et al. “Space-frequency analysis with parallel computing in a phase-sensitive optical time-domain reflectometer distributed sensor” Applied Optics 53 (28), 6586-6590, (2014).

  • X. Hui, et al. “Electro-optic modulator feedback control in phase-sensitive optical time-domain reflectometer distributed sensor” Applied Optics 52 (35), 8581-8585, (2013).

Collaborative Robotic System (work before Cornell)

Major team member in a robotic team. Worked on the navigation control algorithm, motor networks, sensor system (camera and LIDAR) for the Autonomous Robot #2 (with 2 green compress air bottles).

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A photo of the Autonomous Robot #2 worked on.

A video when the robots in a competition. Red team. Autonomous Robot #2 is the one with 2 green compress air bottles

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