Random body movement cancellation in doppler radar vital sign detection

Changzhi Li, Jenshan Lin

Research output: Contribution to journalArticlepeer-review

271 Scopus citations


The complex signal demodulation and the arctangent demodulation are studied for random body movement cancellation in quadrature Doppler radar noncontact vital sign detection. This technique can be used in sleep apnea monitor, lie detector, and baby monitor to eliminate the false alarm caused by random body movement. It is shown that if the dc offset of the baseband signal is accurately calibrated, both demodulation techniques can be used for random body movement cancellation. While the complex signal demodulation is less likely to be affected by a dc offset, the arctangent demodulation has the advantage of eliminating harmonic and intermodulation interference at high carrier frequencies. When the dc offset cannot be accurately calibrated, the complex signal demodulation is more favorable. Ray-tracing model is used to show the effects of constellation deformation and optimum/null detection ambiguity caused by the phase offset due to finite antenna directivity. Experiments have been performed using 47 GHz radar to verify the theory.

Original languageEnglish
Article number4682605
Pages (from-to)3143-3152
Number of pages10
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number12
StatePublished - Dec 2008


  • Arctangent demodulation
  • Complex signal demodulation
  • Dc offset
  • Noncontact
  • Phase offset
  • Random body movement cancellation
  • Ray tracing
  • Vital sign
  • Wireless


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