A new coplanar-fed planar monopole antenna is presented for off-body Ultra-Wideband wearable communication systems. The antenna structure comprises a dome-topped, bowlshaped radiating element and a 50 Ohm coplanar feed line for excitation. Its impedance bandwidth is greater than 118%, from 3.05 to beyond 12 GHz, based on a reflection coefficient smaller than -10 dB criterion. The influence of the human body on the operation of this antenna was studied. In particular, a simplified geometry of a human limb was found to be accurate enough for use in input reflection coefficient simulations. The limb tissues were modeled as frequency-dependent materials. Measurement results show the suitability of the simplified geometry to simulate the antenna in the proximity of a human limb.