Adaptive beam-steering antenna for improved coverage of non-contact vital sign radar detection

This paper presents an adaptive beam-steering antenna for non-contact vital sign radar system at 5.8 GHz. A 2X2 microstrip patch antenna and two phase shifters are manufactured on the same board. Phase shifters consisting of 4 single pole double throw (SPDT) switches are integrated into the matching network of the phase array antenna to save the area. Beam-steering function is controlled by the active phase shifter. The DC bias circuit of the phase shifter is connected with the back side of the antenna through headers. Both simulation and measurement show an antenna bandwidth of 200 MHz centered at 5.8 GHz, which is suitable for a 5.8 GHz non-contact vital sign radar system. The radiation beam of this antenna can steer from -22° to 22° in H-plane, which increases the antenna coverage to 85° without sacrificing antenna gain. Measurement shows the adaptive beam-steering antenna can successfully detect human vital signs while the fixed-beam 2×2 antenna fails due to the limited and fixed antenna beam coverage. The improved performance without increasing antenna area makes the adaptive beam-steering antenna more suitable for commercial application.