A Proximity Coupling RF Sensor for Wrist Pulse Detection Based on Injection-Locked PLL

Byung Hyun Kim, Yunseog Hong, Yong Jun An, Sang Gyu Kim, Hee Jo Lee, Sung Woo Kim, Seung Bum Hong, Gi Ho Yun, Jong Gwan Yook

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


In this paper, a proximity coupling RF sensor based on injection-locked phase-locked loop (PLL) for wrist pulse detection is proposed. The sensor is composed of two main parts: a free-running oscillator and a PLL synthesizer containing a voltage-controlled oscillator. The free-running oscillator is built with a two-port microstrip line resonator (inter-digital electrodes), which acts as part of a transducer that can transform the expansion or contraction of the radial artery into an impedance variation. Measurements show that the impedance variation of the resonator due to changes in the radial artery causes a frequency change of up to 0.74 MHz in the free-running oscillator. For the PLL part, the frequency change can be transformed to a variation in dc voltage by injection of the modulated signal from the wrist pulse into a phase-locked oscillator. The variation of the loop-control voltage, in one cycle of the pulse, is approximately 10-15 mV peak-to-peak. Our sensor is demonstrated to be an effective noncontact and noninvasive scheme for wrist pulse detection.

Original languageEnglish
Article number7462276
Pages (from-to)1667-1676
Number of pages10
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number5
Publication statusPublished - 2016 May

Bibliographical note

Publisher Copyright:
© 2016 IEEE.

All Science Journal Classification (ASJC) codes

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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