Amy Droitcour

Range correlation and I/Q performance benefits in single-chip silicon Doppler radars for noncontact cardiopulmonary monitoring

Direct-conversion microwave Doppler-radar transceivers have been fully integrated in 0.25-/spl mu/m silicon CMOS and BiCMOS technologies. These chips, operating at 1.6 and 2.4 GHz, have detected movement due to heartbeat and respiration 50 cm from the subject, which may be useful in infant and adult apnea monitoring. The range-correlation effect on residual phase noise is a critical factor when detecting small phase fluctuations with a high-phase-noise on-chip oscillator. Phase-noise reduction due to range correlation was experimentally evaluated, and the measured residual phase noise was within 5 dB of predicted values on average. In a direct-conversion receiver, the phase relationship between the received signal and the local oscillator has a significant effect on the demodulation sensitivity, and the null points can be avoided with a quadrature (I/Q) receiver. In this paper, measurements that highlight the performance benefits of an I/Q receiver are presented. While the accuracy of the heart rate measured with the single-channel chip ranges from 40% to 100%, depending on positioning, the quadrature chip accuracy is always better than 80%.

A microwave radio for Doppler radar sensing of vital signs

A microwave radio for Doppler radar sensing of vital signs is described. This radio was developed using custom DCS1800/PCS1900 base station RFICs. It transmits a single tone signal, demodulates the reflected signal, and outputs a baseband signal. If the object that reflects the signal has periodic motion, the magnitude of the baseband output signal is directly proportional to the periodic displacement of the object. When the signal is reflected off a persons chest, this radio with appropriate baseband filters can detect heart and respiration rates from a distance as large as one meter from the target.

Signal-to-Noise Ratio in Doppler Radar System for Heart and Respiratory Rate Measurements

A CMOS Doppler radar sensor has been developed and used to measure motion due to heart and respiration. The quadrature direct-conversion radar transceiver has been fully integrated in 0.25-mum CMOS, the baseband analog signal conditioning has been developed on a printed circuit board, and digital signal processing has been performed in Matlab. The theoretical signal-to-noise ratio (SNR) is derived based on the radar equation, the direct-conversion receivers properties, oscillator phase noise, range correlation, and receiver noise. Heart and respiration signatures and rates have been measured at ranges from 0.5 to 2.0 m on 22 human subjects wearing normal T-shirts. The theoretical SNR expression was validated with this study. The heart rates found with the radar sensor were compared with a three-lead electrocardiogram, and they were within 5 beats/min with 95% confidence for 16 of 22 subjects at a 0.5-m range and 11 of 22 subjects at a 1.0-m range. The respiration rates found with the radar sensor were compared with those found using a piezoelectric respiratory effort belt, and the respiration rates were within five respirations per minute for 18 of 22 subjects at a 0.5-m range, 17 of 22 subjects at a 1.0-m range, and 19 of 22 subjects at a 1.5-m range.

Non-contact respiratory rate measurement validation for hospitalized patients

This paper presents the first clinical results for validating the accuracy of respiratory rate obtained for hospitalized patients using a non-contact, low power 2.4 GHz Doppler radar system. Twenty-four patients were measured in this study. The respiratory rate accuracy was benchmarked against the respiratory rate obtained using Welch Allyn Propaq Encore model 242, the Embla Embletta system with Universal XactTrace respiratory effort sensor and Somnologica for Embletta software, and by counting chest excursions. The 95% limits of agreement between the Doppler radar and reference measurements fall within +/-5 breaths per minute.

Range correlation effect on ISM band I/Q CMOS radar for non-contact vital signs sensing

A quadrature direct conversion microwave Doppler radar has been fully integrated in 0.25 /spl mu/m CMOS. This ISM band radar chip has been used to detect heart and respiration movement 50 cm from the subject. While oscillator phase noise is a performance-limiting factor in CW radar systems, the range correlation effect enables measurement of small phase modulations in spite of the notoriously high phase noise of the on-chip CMOS oscillator. This is the first reported quantitative experimental verification of the range correlation effect.

Applications of MIMO techniques to sensing of cardiopulmonary activity

Remote monitoring of cardiopulmonary activity based on Doppler shifts in radio signals shows promise in medical and security applications, however the problems of motion artifacts and presence of multiple subjects limit the usefulness of this technique. By applying MIMO signal processing, it is possible to overcome limitations of current systems and isolate signals from multiple sources.

Wireless IC Doppler radars for sensing of heart and respiration activity

Remote monitoring of respiration and heart activity can be implemented using wireless communications technology and Doppler radar techniques. Such monitoring has been demonstrated by leveraging existing wireless technology. RFICs developed for wireless base stations have been reused to produce hybrid and fully integrated Doppler radars for vital signs sensing. Heart and respiration activity were observed using these radars at a distance of up to one meter. This technology can potentially enable low-cost, noninvasive long term monitoring of chronic and recovering patients.

Integrated heaters for temperature control in disposable bioassay cartridges for use with portable, battery-operated instruments

Two methods for heating fluids in microliter- to milliliter-scale reaction chambers in disposable bioassay cartridges are analyzed and compared. Inductive heating requires no electrical contact between the energy source and the cartridge and uses a very inexpensive component in the cartridge. Resistive heating with a surface mount component requires electrical interconnection, but is generally conducive to low-cost off-the-shelf components. Typical power consumption for both inductive heating and resistive heating is consistent with battery-powered operation. A finite element model for heating an injection-molded plastic cartridge with a surface-mount resistor has been developed and validated through experiments on a 40 mm × 10 mm × 7.5 mm injection molded polystyrene cartridge with embedded 1kΩ surface-mount resistors. A model of frequency-dependent heat generation in a novel inductive heating device is also presented.

Modified silicon base station chips as biomedical sensors

Subcircuits designed for DCS1800/PCS1900 base stations have been reconfigured into single-chip Doppler radar transceivers. Three of these radar chips have been fully integrated in 0.25 /spl mu/m silicon CMOS and BiCMOS, and they have been used to remotely monitor heart and respiration activity. These radar chips have detected heartbeat and respiration rate 50 cm from the subject, which may be useful in home monitoring, continuous monitoring, and physiological research.