Abstract
This paper considers design of microstrip MIMO antennas for an LTE/WiMAX USB dongle operating in the 2.5–2.7 GHz frequency band. The MIMO system includes two antenna elements with an additional requirement of high isolation between them that is especially difficult to realize due to size limitations of a USB dongle. Three approaches to achieve the needed system characteristics using microstrip PCB antennas are proposed. For the first design, high port-to-port isolation is achieved by using a decoupling techniques based on a direct connection of the antenna elements. For the second approach, high port-to-port isolation of the MIMO antenna system is realized by a lumped decorrelation capacitance between antenna elements feeding points. The third proposed antenna system does not use any special techniques, and high port-to-port isolation is achieved by using only the properties of a developed printed inverted-F antenna element. The designed MIMO antenna systems have the return loss S11and the insertion loss S21bandwidths of more than 200 MHz at the −8 dB level with the correlation coefficient lower than 0.1 and exhibit pattern diversity when different antenna elements are excited. Experimental measurements of the fabricated antenna systems proved the characteristics obtained from electromagnetic simulation.
Highlights
Modern wireless communication systems should simultaneously provide high reliability and channel capacity
The designed antenna system in [9] uses the diversity technique based on direct connection of the antenna elements for providing high port-to-port isolation in the frequency band around 700 MHz while the diversity in the 2.5–2.7 GHz band is achieved by conventional spatial diversity with large antenna elements separation
This work presented the three different microstrip MIMO antenna system designs for long-term evolution (LTE)/WiMAX USB dongle applications operating in the 2.5–2.7 GHz frequency band
Summary
Modern wireless communication systems should simultaneously provide high reliability and channel capacity. Many works were focused on developing special techniques that allow increasing the isolation between the antenna elements in a MIMO antenna system These diversity techniques are based on different approaches: defected ground structures [2], split ring resonators [3], the electromagnetic bandgaps [4], or utilize a coupling antenna element between the antennas [5]. The designed antenna system in [9] uses the diversity technique based on direct connection of the antenna elements for providing high port-to-port isolation in the frequency band around 700 MHz while the diversity in the 2.5–2.7 GHz band is achieved by conventional spatial diversity with large antenna elements separation. This work aims to design a planar microstrip twoelement MIMO antenna system operating in the 2.5– 2.7 GHz frequency band for the application in modern USB dongles for LTE or WiMAX communication systems.
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