Design of multiband MIMO antenna in compact mobile handsets and SAR distribution

The Multiband antenna for mobile applications operating in GSM, DCS, PCS, UMTS, Bluetooth and LTE bands has implemented in HFSS 13.0 of the dimension 110*50*1 mm³. The idea of multiband antenna has carried out in designing the MIMO mobile handset antenna in CST studio. It consists of a pair of printed MIMO antennas for mobile handsets. Each antenna being a coupled fed monopole in a meandered shape, is capable of covering GSM 1800/1900, UMTS, WLAN and LTE frequency bands. The antennas are fixture diagonally at the non-grounded portion of the circuit board. The substrate used for the circuit board is FR4 with relative permittivity of 4.4 and loss tangent of 0.02. The overall volume of the circuit board is 110 × 65 × 0.8 mm³ with each antenna occupying an area of 24 × 14.5 mm². Since mutual coupling is the major problem, hence to improve the isolation between antennas, dual decoupling structures consisting of ground slots and inverted L ground branches that extend into the non-grounded portion are etched diagonally on the bottom layer of the substrate. The isolation achieved is better than 15 dB over all the frequency bands covered by each antenna leading to an envelope correlation coefficient of less than 0.02. SAR performance also described and measured SAR value meets the industry standards.