Study of UWB half-ellipse antenna with a shallow backed cavity in vital sign detection

The impulse radar is an effective tool for nondestructive subsurface sensing. In this paper, a shallow back-cavity shielded planar dipole antenna used in a Vital Sign Detection radar consisting of two half-elliptical-shape arms and working at 400MHz is investigated numerically and experimentally. The voltage standing wave ratio (VSWR) and radiated waveforms are analyzed. A loading technique for improving pulse radiation and reducing late-time ringing is introduced. The presented antenna characteristic is compared with one bowtie antenna in the same dimensions. The influence of the shallow cavity to the antenna characteristic is also presented. The designed antenna is fabricated and also applied to a vital sign detection system. Tested data shows that the back-cavity shielded antenna works satisfactorily in the prototype system.