Comparison of a monopole and a PIFA handset antenna in the presence of the human head

The great majority of wireless devices, such as handset phones, are used close to the human head. This fact modifies the antenna performance compared with a free space scenario. One of the critical aspects is that the human head absorbs power from the antenna radiation. In this sense, it is necessary to reduce such absorption not only to minimize the temperature inside the head, but also to increase the radiated power to free-space. The performance associated to two types of handset antennas, a monopole and a planar inverted-F antenna (PIFA) is evaluated regarding the presence of the human head. The most significant parameters (reflection coefficient, efficiency, and specific absorption rate) are measured for two different positions of the antenna (handset having the antenna close to the ear and the other when the handset is rotated 180°) as a function of the low frequency region (∼ 824-960 MHz) and high frequency region (∼1710-2170 MHz). Despite the monopole presented here occupies less space and covers more bands regarding free-space conditions, the PIFA under analysis becomes more robust to the human head loading effect.