The RF sensors operates on Doppler principal. Under this scenario the efficient transceiving element is the key for its success in the detection of tiny human vital signs. Antenna is a device acting as a transition element between RF front end circuitry and free space. Further, it must be a low cost, compact and reliable structure. This section describes the state-of-the art in antenna design along with design and prototyping of various antenna structures useful as the transceiving element in the RF sensor.