An apparatus comprises a processor (101) configured to control generation of an ultra-wideband radar signal and reception of one or more resultant signals； a transmit antenna (104) configured to output the ultra-wideband radar signal directed at biological tissue； and a receive antenna (105) configured to receive the one or more resultant signals based on a reflection of the ultra-wideband radar signal from the biological tissue. The transmit antenna is positioned at a fixed angle relative to the receive antenna.The apparatus may be embodied in a wearable device.
