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7 - Noise- and Interference-Reduction Methods for Microwave Doppler Radar Vital Signs Monitors

By
Isar Mostafanezhad ,
Olga Boric-Lubecke ,
Danilo Mandic  and
Ehsan Yavari
Edited by
Isar Mostafanezhad ,
Olga Boric-Lubecke  and
Jenshan Lin
Isar Mostafanezhad
Affiliation:
University of Hawaii at Manoa
Olga Boric-Lubecke
Affiliation:
University of Hawaii at Manoa
Danilo Mandic
Affiliation:
Imperial College London
Ehsan Yavari
Affiliation:
University of Hawaii
Isar Mostafanezhad
Affiliation:
University of Hawaii, Manoa
Olga Boric-Lubecke
Affiliation:
University of Hawaii, Manoa
Jenshan Lin
Affiliation:
University of Florida
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Summary

Introduction

Doppler radar has recently been extensively used in noncontact cardiopulmonary monitoring [1–3]. A continuous wave (CW) microwave signal is transmitted toward a human subject. Physical motion caused by the respiration and heartbeat of the human subject phase modulates the transmitted signal and reflects it back to the transmit antenna, where it is received and phase demodulated to yield the heart and respiration rates of the subject. Physical motion of the human chest during respiration and heart motion are measured to be about 0.2 to 2 and 8 to 20 mm, respectively [4]. Thus the system has to be very sensitive to phase changes, which are caused by path-length variations. For a stationary transmitter and subject, this path length only varies with a subject's heartbeat and respiration. A nonstationary transceiver antenna or a fidgeting subject will produce additional path variations causing interference in radar signal (Figure 7.1).

There are cases where the transmit/receive antenna cannot be assumed to be physically stationary. For example, if the transceiver is a handheld unit used in search and rescue operations or to sense through walls in military applications, “hand shake” of the operator will introduce path-length variations that phase modulate the received signal in addition to that of the target's cardiopulmonary motion. Also, if the antenna is placed on a platform subject to some vibration, the vibration can cause antenna motion, creating an interference with the radar signal. Monitoring a driver in a vehicle is an example of such an application. Thus the final demodulated signal will include components resulting from operator's unwanted hand shake to the extent that life signs monitoring will become impossible due to excessive interference. The fidgeting of the subject, which can be the result of coughing, sneezing, itching, and similar activities, is another source of this type of interference.

While most sources of unwanted interference motion are random, they can still be categorized to a certain extent by their frequency spectrum and amplitude. For example, a 2003 Ford Taurus with a V6 engine being driven on a flat freeway at a speed of 65 mph creates about 3 to 9 mm of shake at a low frequency of 1.2 Hz [5].

The problem of undesired instrument shake is similar in still image and video cameras, where it causes motion blur in the captured image.

Type
Chapter
Information
Medical and Biological Microwave Sensors and Systems
, pp. 202 - 227
Publisher: Cambridge University Press
Print publication year: 2017

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References

[1] Lin, J. C., “Noninvasive microwave measurement of respiration,” Proc. IEEE 63(10) (1975): 1530.CrossRefGoogle Scholar
[2] Lubecke, V.M., Boric-Lubecke, O., Awater, G., Ong, P.-W., Gammel, P., et al., “Remote sensing of vital signs with telecommunications signals,” presented at the World Congress on Medical Physics and Biomedical Engineering (WC2000), Chicago, July 2000.
[3] Droitcour, A., Lubecke, V. M., Lin, J., and Boric-Lubecke, Olga, “A microwave radio for Doppler radar sensing of vital signs,” in IEEE MTT-S International Microwave Symposium Digest, vol. 1 (Piscataway, NJ: IEEE, 2001), pp. 175–8.Google Scholar
[4] Droitcour, A. D., “Non-contact measurement of heart and respiration rates with a single-chip microwave doppler radar,” Ph.D. dissertation, Stanford University, 2006.
[5] www.vibrationdata.com/Newsletters/August2004_NL.pdf.
[6] Razligh, Q. R. and Kehtarnavaz, N., “Image blur reduction for cell-phone cameras via adaptive tonal correction,” in 2007 IEEE International Conference on Image Processing (IEEE ICIP 2007), vol. 1 (Piscataway, NJ: IEEE, 2007), pp. I-113–I-116.Google Scholar
[7] Greneker, E. et al., “Stabilizing motion in a radar detection system using ultrasound radar range information,” United States Patent no. 6909397, June 21, 2005.
[8] Mostafanezhad, I., Park, B. K., Boric-Lubecke, O., Lubecke, V., and Host-Madsen, Anders, “Sensor nodes for doppler radar measurements of life signs,” in IEEE MTT-S International Microwave Symposium Digest, vol. 1 (Piscataway, NJ: IEEE, 2007), pp. 1241–4.Google Scholar
[9] Mostafanezhad, I., Boric-Lubecke, O., Lubecke, V., and Host-Madsen, A., “Cancellation of unwanted motion in a handheld Doppler radar used for life sign monitoring,” in IEEE MTT-S International Microwave Symposium Digest (Piscataway, NJ: IEEE, 2008).Google Scholar
[10] Park, B.-K., Boric-Lubecke, O., and Lubecke, V. M., “Arctangent demodulation with dc offset compensation in quadrature Doppler radar receiver systems,” IEEE Trans. Microwave Theory Tech. 55(5) (2007): 1073–9.CrossRefGoogle Scholar
[11] Lohman, B., Boric-Lubecke, O., Lubecke, V. M., Ong, P. W., and Sondhi, M. M., “A digital signal processor for Doppler radar sensing of vital signs,” in Proceedings Of the 23rd Annual Engineering in Medicine and Biology Society Conference, vol. 4 (Piscataway, NJ: IEEE, 2001), pp. 3359–62.Google Scholar
[12] Huang, N. E., Shen, Z., Long, S. R., Wu, M. C., Shih, H. H., et al., “The empirical mode decomposition and the Hilbert spectrum from nonlinear and non-stationary time series analysis,” Proc. R. Soc. Lond. A 454 (1998): 903–95.CrossRefGoogle Scholar
[13] Mandic, D., Golz, M., Kuh, A., Obradovic, D., and Tanaka, T. (eds.), Signal Processing Techniques for Knowledge Extraction and Information Fusion (New York: Springer, 2008).CrossRefGoogle Scholar
[14] Flandrin, P., Rilling, G., and Goncalves, P., “Empirical mode decomposition as a filter bank,” IEEE Signal Process. Lett. 11(2) (2004): 112–14.CrossRefGoogle Scholar
[15] Liu, S., He, Q., Gao, R. X., and Freedson, P., “Empirical mode decomposition applied to tissue artifact removal from respiratory signals,” in 2008 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBS Conference), vol.1 (Piscataway, NJ: IEEE, 2008), pp. 3624–7.Google Scholar
[16] Rilling, G., Flandrin, P., “One or two frequencies? The empirical model decomposition answers,” IEEE Trans. Signal Process. 56(1) (2007): 85–95.Google Scholar
[17] Mostafanezhad, I., Boric-Lubecke, O., Lubecke, V., and Mandic, D., “Cancellation of unwanted Doppler radar sensor motion using empirical mode decomposition,” IEEE Sensors J. 13(5): 1897–904.
[18] Mostafanezhad, I., Yavari, E., Boric-Lubecke, O., Lubecke, V., and Mandic, D., “Application of empirical mode decomposition in removing fidgeting interference in Doppler radar life signs monitoring devices,” IEEE Sensors J. 13(5) (2013): 1897–1904.Google Scholar
[19] Massagram, W. J., “A study of feasibility in long-term cardiopulmonary monitoring via Doppler radar,” Ph.D. dissertation, University of Hawaii at Manoa, 2008.
[20] “Codes for MATLAB implementation of EMD,” available at http://perso.ens-lyon.fr/patrick.flandrin/emd.html.
[21] Wu, Z. and Huang, N. E., “Ensemble empirical mode decomposition: a noise assisted data analysis method,” available at ftp://grads.iges.org/pub/ctr/ctr_193.pdf.
[22] Park, B., “Cardiopulmonary monitoring using Doppler radar,” Ph.D. dissertation, University of Hawaii at Manoa, 2007.
[23] Droitcour, A., Boric-Lubecke, O., and Kovacs, G., “Signal-to-noise ratio in Doppler radar system for heart and respiratory rate measurements,” IEEE Trans. Microwave Theory Techn. 57(10) (2009): 2498–507.CrossRefGoogle Scholar
[24] Massagram, W., Lubecke, V. M., Host-Madsten, A., and Boric-Lubecke, O., “Assessment of heart rate variability and respiratory sinus arrythmia via Doppler radar,” IEEE Trans. Microwave Theory Techn. 57(10) (2009): 2542–9.CrossRefGoogle Scholar

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