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Low-profile switchable LTE/WWAN MIMO antenna system

ABSTRACT This study proposes a low-profile switchable LTE/WWAN multi-input and multi-output (MIMO) antenna system for laptops. The main and auxiliary antennas, mirror-imaged of each other, are configured on the left and right sides of the top edge of the display ground plane. The two antennas are each a planar inverted-F antenna (PIFA) having the size of 102 × 5 × 3 mm3. The PIFA structure is matched in impedance with a set of reactive chip elements to increase the antenna operating bandwidth, and is combined with a set of switchable circuits to change the low-frequency resonant path in accordance with the switch status, ON or OFF, thus allowing the low-frequency modes to cover the LTE700 and GSM850/900 bands. Without any isolation element, an isolation of 15 dB or more can be achieved in the MIMO antenna system. The measured realized antenna efficiency is also 48% or greater.