A K-band sensor interface design for remote cardiorespiratory sensing and monitoring

Abstract

The need for a contact-less cardiorespiratory measurement made many researchers put their e orts on this matter. There are many di erent approaches to this issue. From ow of the air in and out of the mouth [1] to image processing of a camera [2]. A technique based on Doppler e ect to detect movement in patient's chest wall is used. This movement contains many di erent kinds of data such as breathing movement, heartbeat, and random muscle twitches. In addition, we receive signal from stationary environment as well as dynamic objects and people around the patient. That is the reason why we need to precisely lter out the unwanted data in order to obtain the bio-signals successfully. A system has been designed and its functionality tested. An analog circuit manages the input signal coming from the K-band sensor. Filtering and ampli cation are done in this block. An automatic gain control (AGC) unit is also designed and used to maintain the output signal amplitude so that we can use the highest e ciency possible from analog to digital converter (ADC). The signal is then converted to digital and the relative movement is calculated in an arm-based processor. Then, the data are sent to the monitoring terminal using user datagram protocol (UDP). In the monitoring terminal, several digital signal processing steps are taken to visualize the signal in time domain, frequency domain, and spectrogram. A graphical user interface (GUI) is designed for easier observation of life signs. Additionally, three similar systems are fabricated and placed in three di erent locations, all of them connected to a server. This makes it possible to monitor the conditions of multiple patients at the same time and using this idea, we created a medical hub, which can be placed in a hospital to help monitor patients inside their home or in di erent rooms in hospital.