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

Modulate the vital signs of a person onto multiplexed RF signals, including the heart rate, the respiration rate, the breath effort, and the blood pressure.

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

Wireless version NCS system illustration by Nature News.


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

Designed an intelligent non-linear transmission line tag. Combined with the second harmonic reader, the tag’s ID and accurate (50 microns in air, 5 microns in water with 915 MHz system) ranging and (millimeters) position can be obtained. The system is not limited by the Uncertity Priciple from Fourier transform mathematical model, so the high spacial 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.

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.

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. 

NCS Bird.png

Schematic of the wireless NCS system

Real-time heartbeat and breath monitoring of a parakeet.


CDMA protocols in Harmonic RFID System

The CDMA protocols are developed for the harmonic RFID tags and collaborative readers. The protocols provide better tag access synchronization, noise performance and tag yield rate.

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.

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)

Utilize the UHF RFID system to get the microwave images of the people in indoor environment. The RFID tag and reader antennas compose a multistatic microwave imaging system.

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.

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, Supported by 973-Funding Agency)

With a 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.

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).

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