Compact planar inverted-F antenna system for MIMO USB dongle operating in 2.5—2.7 GHz band

This paper presents a design of a compact planar MIMO antenna system for an LTE/WiMAX USB dongle operating in the 2.5-2.7 GHz frequency band. The proposed MIMO antenna system consists of two planar inverted-F antenna elements with high isolation between them. The high isolation is achieved by mirror symmetrical orientation of the developed printed inverted-F antenna elements relative to each other. This provides pattern diversity between the two different antenna elements. The antenna system is realized using the standard FR4 PCB substrate that leads to a low production cost. The occupied antenna area has the dimensions of 21.5 mm × 20 mm that is only a fraction of the operating wavelength (115 mm at 2.6 GHz). The designed MIMO antenna system has the bandwidth of more than 200 MHz at the reflection coefficient level below -8 dB. The isolation between the antenna elements across the radiation bandwidth exceeds 8.5 dB and the envelope correlation coefficient is lower than 0.1. Experimental measurements of the fabricated antenna system confirm the results of electromagnetic simulation.