Phased array antennas for personal communications handsets

Abstract

A two element phased array is considered for use in a personal communications handset working at frequencies near 2 GHz. The interaction with the user's head is modelled approximately using the method of spherical wave expansions, treating the head as a two-layered dielectric sphere. By designing the array to radiate away from the head, overall efficiency and azimuth coverage are simultaneously improved, and user exposure is reduced. Improved results are obtained when the excitation ratio is chosen to produce a null field at a near field point on the head surface near the antenna. This requires a substantial increase in the relative excitation of the outer radiating element, as compared with a conventional cardioid pattern array. The peak specific absorption rate can be reduced by at least 15 dB.