Reducing User Effects on Mobile Handset Antennas Using Mode Mapping

In this work, we investigate how different radiation patterns are influenced by the user’s hand, based on which we design handset antennas that are robust to the hand effect. Handset antenna working at dual bands is firstly simulated numerically, with its eigenvalues, characteristic currents and farfields calculated over the frequency bands. Afterwards, the total pattern of the antenna is mapped to its characteristic patterns using weighting coefficients. To study the influence of the hand on each modal pattern, the pattern for the antenna with hand is then obtained. Similar to the free space scenario, the pattern with hand is also mapped to the characteristic patterns in free space. Comparing the weighting coefficients of each mode in free space and with hand, it is derived that the radiation pattern with null at the boresight is less affected by the hand. According to the observation, a handset antenna, which radiates little power towards the boresight, is designed. It is proved that the radiation efficiency of the proposed antenna with hand is 2.4 dB higher than that of the reference antenna.