Interaction between the Radiation of LTE MIMO Antennas in a Mobile Handset and the User´s Body

Abstract: Due to the great demand for high-speed wireless communication, Multi Input Multi Output (MIMO) antenna systems have been attracted rapidly increased attention. Therefore, the interaction between human body and MIMO antenna becomes an important issue, which will be studied in the present thesis. This thesis mainly focuses on the specific absorption rate (SAR) of the LTE MIMO antenna in mobile phone. It is different from the SISO antenna, and as the MIMO antenna has more operation modes and functions (MIMO, SISO, beam forming, etc.), more parameters need to be investigated for the SAR of the antenna. In this thesis, four designs of dual elements MIMO antenna (dual semi ground free PIFA, co-located antenna, dual OG PIFA in parallel position and dual OG PIFA in orthogonal position) are studied under four typical LTE frequency points (0.75GHz, 0.85GHz 1.9Ghz and 2.1/2.6GHz), with the effects of different chassis lengths (90mm, 110mm, 130mm and 150mm), the port’s states (terminated with 50ohm, open or short) and phase difference (0 degree to 360 degree). The SAR, when dual elements operate simultaneously, is also studied, which is evaluated by the SAR to PEAK Location Spacing Ratio (SPLSR). The simulations are run on both a SAM head phantom and a flat phantom by CST 2011, and measurements on flat phantom are carried out with iSAR and Dasy to verify the accuracy of our simulations. Besides SAR, the body loss of MIMO and SISO LTE antennas (MIMO: dual semi ground free PIFA and co-located Antenna; SISO: OG PIFA on top and OG PIFA at the bottom) in mobile phones are also studied in this thesis. The body loss and multiplex efficiency (MUX) with head and hand (H+H) in an increased cell phone case length (110mm, 130mm and 150mm) are investigated and discussed. Furthermore, some prominent problems in body loss study (body loss reduction, right and left hand problem, etc.) are also discussed in this thesis.