Abstract
Abstract. Radar systems for contactless vital sign monitoring are well known and an actual object of research. These radar-based sensors could be used for monitoring of elderly people in their homes but also for detecting the activity of prisoners and to control electrical devices (light, audio, etc.) in smart living environments. Mostly these sensors are foreseen to be mounted on the ceiling in the middle of a room. In retirement homes the rooms are mostly rectangular and of standardized size. Furniture like beds and seating are found at the borders or the corners of the room. As the propagation path from the center of the room ceiling to the borders and corners of a room is 1.4 and 1.7 time longer the power reflected by people located there is 6 or even 10 dB lower than if located in the center of the room. Furthermore classical antennas in microstrip technology are strengthening radiation in broadside direction. Radar systems with only one single planar antenna must be mounted horizontally aligned when measuring in all directions. Thus an antenna pattern which is increasing radiation in the room corners and borders for compensation of free space loss is needed. In this contribution a specification of classical room sizes in retirement homes are given. A method for shaping the antenna gain in the E-plane by an one-dimensional series-fed traveling wave patch array and in the H-plane by an antenna feeding network for improvement of people detection in the room borders and corners is presented for a 24 GHz digital beamforming (DBF) radar system. The feeding network is a parallel-fed power divider for microstrip patch antennas at 24 GHz. Both approaches are explained in theory. The design parameters and the layout of the antennas are given. The simulation of the antenna arrays are executed with CST MWS. Simulations and measurements of the proposed antennas are compared to each other. Both antennas are used for the transmit and the receive channel either. The sensor topology of the radar system is explained. Furthermore the measurement results of the protoype are presented and discussed.
Highlights
Because of the rising amount of elderly people in retirement homes and the non-continuous observation by caretakers, the early recognition of emergencies should be improved further
The goal is to achieve a non-invasive alternative with a planar microstrip patch antenna based radar system which can monitor people’s vital signs while they move freely around in their home
Many activities are based on standard radar systems with conventional antenna designs and by optimizing the signal processing (Will et al, 2015)
Summary
Because of the rising amount of elderly people in retirement homes and the non-continuous observation by caretakers, the early recognition of emergencies should be improved further. The goal is to achieve a non-invasive alternative with a planar microstrip patch antenna based radar system which can monitor people’s vital signs while they move freely around in their home. Many activities are based on standard radar systems (classical CW or FMCW systems) with conventional antenna designs and by optimizing the signal processing (Will et al, 2015). In two former conference contributions the authors have shown in detail the concept of the antenna design for monitoring elderly people in retirement homes (Schäfer et al, 2018a, b). A parallel feeding network (PFN) for the individual line arrays is designed in order to compensate the gain in the H-plane. 4 the transmission characteristics and the feeding network design will be described and the microstrip patch antennas are shown.
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