This paper studies the effect of incident wave angular power spectrum (APS) distribution and user hand effect on the envelope correlation coefficient (ECC) of two port MIMO antenna operating in frequency band of LTE-U sub 6 GHz. APS of uniform and Gaussian distributions are used with different Gaussian angular spread (AS) values i.e. 10˚, 30˚, 50˚ and 70˚. A prototype was fabricated, and three-dimensional radiation patterns of antenna elements were measured in anechoic chamber from 4 to 6 GHz in both cases of free space and when the user hand phantom grips the prototype in data mode. An algorithm to calculate ECC from the complex data of far field radiation pattern with different APS distributions is explained in details. Results show that user hand presence increases ECC between ports compare with free space, whose increase is more obvious under Gaussian APS. ECC values under uniform APS is practically zero over the entire frequency range expect at frequency values close to 6 GHz where the highest ECC values are 0.13 and 0.16 in free space and with user hand respectively. However, Gaussian APS with different AS's shows a significant impact of the ECC. With narrow AS of 10˚, ECC at some incident directions can be as high as 0.84 and 0.92 in free space and with user hand respectively and the mean ECC values under this AS are 0.25 and 0.37 respectively. ECC values keep decreasing as AS gets wider, at AS = 70˚, maximum ECC values are 0.23 and 0.34 in free space and with user hand respectively with mean values close to uniform APS. Statistical distribution of ECC show good agreement with exponential distribution, more agreement between measured ECC and exponential distribution is observed in free space with wider AS.
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