CUSTOMIZED NON-CONTACT CARDIO-RESPIRATORY MONITORING
Bioradar is a short range, low power, and light weight compact radar to be used for non-contacting monitoring specific biometric modulations, such as heart beat, respiration or other biometric patterns induced by micro movements of human body. One application of the bio-radar is to monitor human sleep pattern for diagnosis of obstructive sleep apnea syndrome (OSAS) or detection of sudden infant death syndrome (SIDS) during sleep. OSA is a common, widely underdiagnosed condition associated with significant morbidity and mortality. Due to intermittent anatomical blockage of the upper airway, reduction or even cessation of airflow occurs during sleeping, resulting in recurrent oxygen desaturation and sleep fragmentation.
Due to the weakness of biometric modulated signals by heart beats and breathing, any environmental clutter, multipath propagation, undesired direct coupling effect from transmitted energy, system flicker noise, and other causes can overwhelm the biometric signals. Thus, the desired bio-radar must have powerful processor for effectively extracting informative biometric signals and estimating physiological parameters.
Based on our experiences in developing software defined RF modules, processor modules and system applications, we are capable of making customized SDR RF/Processor circuit board and software package for realizing the bio-radar with high sensitivity.
Our software-defined radar architecture offers a great deal on system compactness and flexibility. We use a special designed digital signal processor dealing with environmental clutter, multipath, DC coupling effect, and flicker noise to achieve high sensitivity for better extraction of biometric information. Our customized specifications for the bio-radar include:
- Frequency Band: C-band centered at 5.8 GHz (ISM band), X-band centered at 9.8 GHz, or K-band centered at 24.125 GHz (ISM band).
- Radar Signal Waveform: FMCW (frequency modulated continuous wave) and CW.
- Signal Bandwidth: 150 MHz, 250 MHz and expanded bandwidth up to 2 GHz.
- Dynamic Range: > 60 dB
- Phase Noise: < -100 dBc
- Monitoring Range: 0 – 20 m
Bioradar System Architecture
Compared to the conventional homodyne receiver, super-heterodyne receiver has significant higher sensitivity. Its IF-signal is well above the flicker noise. Thus, the flicker noise of the first mixer will not pass through the IF amplifier. The amplified IF signal is much larger than the flicker noise of the second mixer and, thus, flicker noise can be significantly reduced. In the processor module, the respiration and heartbeat signals are extracted separately. The bio-radar system architecture is illustrated below:
We have tested the bio-radar to extract human respiration pattern and heartbeat pattern using our SDR-KIT 980B centered at 9.8 GHz with 400 MHz bandwidth as below. The respiration pattern and heartbeat pattern are extracted from the respiration processor and the heartbeat processor separately. The extracted respiration pattern shows the respiration period of 2-3 sec and the heartbeat period of around 1 sec as blow: