Mobile Phone EMC Deterioration Due to Difierent Realistic Usage Patterns

This paper presents in details the efiects of difierent realistic usage patterns on the EMC, that represented by the antenna total e-ciency (·tot) and the total isotropic sensitivity (TIS), of difierent mobile phone handsets, where a commercial FDTD-based EM solver is used to solve Maxwell's equations. Difierent semi-realistic mobile phone handset models operating in the GSM900, GSM1800, and UMTS/IMT-2000 bands are simulated to achieve the available commercial models, whereas, a heterogeneous MRI-based CAD model is used to simulate the mobile phone user's head. The results achieved in this paper showed that certain realistic usage patterns during a call could dramatically afiect the mobile phone antenna speciflcations, i.e., ·tot, and TIS, and consequently deteriorate its EMC. 1. INTRODUCTION While moving towards a ubiquitous society where anyone can get information from anywhere at any time, antennas are becoming a key component for cellular handsets and other portable wireless devices. Users of portable wireless devices want such devices to be of small volume, light weight, and low cost. With the huge progress in very large scale integration (VLSI) technology, this dream has become a reality in the past two decades. All that imposed a big challenge to engineers in keeping the mobile phone handset compatible electromagnetically. From a more technical point of view, the user's body, head and hand, have an impact on the mobile handset. The tissue of the user represents a large dielectric and lossy material distribution in the near fleld of a radiator. It is obvious, therefore, that all antenna parameters, such as impedance, radiation characteristic, radiation e-ciency and total isotropic sensitivity (TIS), will be afiected by the properties of the tissue. Moreover, the efiect can difier with respect to the individual habits of the user in placing his hand around the mobile handset or attaching the handset to the head. Optimized user interaction, therefore, becomes a technical performance parameter of cellular mobile phones. The electromagnetic interaction between mobile phone antenna and human body was investigated extensively in the previous literatures, where a review of the most published articles in this fleld can be found in (1), whereas, the Electromagnetic Compatibility (EMC) of mobile phone antennas are studied by few authors (2,3). The EMC of a cellular handset is deflned as its ability to function properly in its intended electromagnetic environment and without introducing excessive electromagnetic energy that may interfere with other devices. This paper investigated the mobile phone EMC, that represented in terms of total e-ciency (·tot) and TIS deterioration due to difierent realistic usage patterns, where both ·tot and TIS are computed due to difierent handhold and handset positions. 2. MOBILE PHONE ANTENNA EFFICINCY AND TIS 2.1. Antenna Total E-ciency (·tot) The e-ciency of a handset antenna is the ratio of the total power radiated by the antenna to the forward power available at its terminals (or those of its associated matching network). The antenna e-ciency is a parameter which takes into account the amount of losses at the terminals of the antenna and within the structure of the antenna. These losses are: re∞ections because of mismatch between the transmitter and the antenna, and I 2 R losses (conduction and dielectric). Hence the total antenna e-ciency can be written as: ·tot = ·mis ¢ ·c ¢ ·d