Wireless RF Vital Signal Sensor Using Autoregressive Spectral Estimation Method

This letter describes a compact and novel wireless vital signal sensor at 2.4 GHz that can detect heartbeat and respiration signals. The oscillator circuit incorporates a planar resonator, which functions as a series feedback element as well as a near-field radiator. The periodic movement of the body during aerobic exercise causes an input impedance variation of the radiator within the near-field range. This variation results in a corresponding change in the oscillation frequency, and this change has been utilized for detection of human vital signals. In addition, a surface acoustic wave (SAW) filter and power detector have been used to increase the system sensitivity and to transform the frequency variation into a voltage waveform. Also, the autoregressive spectral estimation method is applied to achieve precise vital sign detection. The experimental results show that the proposed sensor placed 20 mm away from a human body can detect the vital signals very accurately.

[1]  C Gabriel,et al.  The dielectric properties of biological tissues: I. Literature survey. , 1996, Physics in medicine and biology.

[2]  Jong-Gwan Yook,et al.  5.8 GHz Vital Signal Sensing Doppler radar using Isolation-improved Branch-line Coupler , 2006, 2006 European Radar Conference.

[3]  Jeremy Everard.  Fundamentals of RF circuit design : with low noise oscillators , 2001 .

[4]  Jenshan Lin,et al.  0.25 /spl mu/m CMOS and BiCMOS single-chip direct-conversion Doppler radars for remote sensing of vital signs , 2002, 2002 IEEE International Solid-State Circuits Conference. Digest of Technical Papers (Cat. No.02CH37315).

[5]  Randall W. Rhea,et al.  Oscillator design and computer simulation , 1990 .

[6]  J. M. Spyers-Ashby,et al.  A comparison of fast fourier transform (FFT) and autoregressive (AR) spectral estimation techniques for the analysis of tremor data , 1998, Journal of Neuroscience Methods.

[7]  K. Ura,et al.  Noise Analysis of Nonlinear Feedback Oscillator with AM-PM Conversion Coefficient , 1980 .

[8]  P. C. Richardson,et al.  Capacitive electrocardiographic and bioelectric electrodes. , 1969, IEEE transactions on bio-medical engineering.

[9]  A.E. Fathy,et al.  Through-the-Wall Radar Life Detection and Monitoring , 2007, 2007 IEEE/MTT-S International Microwave Symposium.

[10]  Tsuyoshi Kato,et al.  Capacitive Sensing of Electrocardiographic Potential Through Cloth From the Dorsal Surface of the Body in a Supine Position: A Preliminary Study , 2007, IEEE Transactions on Biomedical Engineering.

[11]  Tzyy-Ping Jung,et al.  A brain-machine interface using dry-contact, low-noise EEG sensors , 2008, 2008 IEEE International Symposium on Circuits and Systems.