Investigation of parasitic elements for coupling reduction in multiantenna hand-set devices
This article investigates parasitic radiating structures for coupling reduction between two 900MHz planar inverted-F antennas (PIFAs) in a hand-held device. Measurement of the initial prototype shows that a maximum isolation enhancement of more than 8 dB is achieved with a single parasitic element. This is followed by optimization of the parasitic structure for compactness, improved bandwidth, and tuning capability. First, different techniques for miniaturization are employed to obtain 60% less footprint with a 22 mm x 15 mm meandered parasitic element. Second, it is demonstrated that the isolation bandwidth can be increased by employing several parasitic radiators with different lengths. Finally, it is presented that the operation of a handheld device, as well as the coupling reduction technique, is compromised in proximity to the human body. For the first time, a miniaturized electronically tunable parasitic radiating element is designed to compensate for the detuning of the coupling reduction technique and adjusting its resonance to achieve maximum isolation between two handset PIFAs. Measurements of the fabricated prototype show 810960 MHz tuning range.  2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:110, 2014.
multiantenna structures multiple-input multiple-output (mimo) systems mutual coupling wireless communication