Isolation enhancment of two planar monopole antennas for MIMO wireless applications

This paper presents a planar slotted meander line structure to reduce the mutual coupling between two microstrip fed planar monopole patch antennas. The array provides a relative operating bandwidth of 98 % (1.37-4.00) GHz matched at a reflection coefficient S11 and S22 less than -10 dB with a total realized gain of 3.9, 4.66, and 4 dB at 1.85, 2.4, and 3.5 GHz respectively. The isolation level has been reduced to less than -20 dB for a wide frequency band of 85 % (1.46-3.64) GHz. The design represents a good candidate for modern wireless standards utilizing MIMO techniques including 3GPP LTE, WiMAX, WiFi, as well as systems utilizing ISM spectrum equipped with multiple antennas.