A novel 4-element Multi-Input Multi-Output (MIMO) array antenna is proposed for Dedicated Short Range Communications (DSRC), Wireless Local Area Network (WLAN), and X-band applications. The proposed antenna is a microstrip antenna that consists of a simple square patch as radiating element with a defected ground structure (DGS). Dimensions of the proposed antenna are very compact with size 40 × 48 × 0.8 mm 3 . It operates from 5.6-6.1 GHz (DSRC/WLAN) and 8.7-10.8 GHz (X-band) with impedance

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... widths (S 11 <= −10 dB) of 500 MHz and 2.1 GHz, respectively. The isolation between elements of MIMO is also greater than 25 dB in the operating bands. Antenna performance parameters are investigated at 5.9 GHz and 10.5 GHz center frequencies and computersimulated, and experimentally measured characteristics are found to be satisfactory. A peak gain of 4.8 dB is achieved, and radiation efficiency is also greater than 75% in operating bands. Envelope Correlation Coefficient (ECC) is less than 0.05, and Diversity Gain (DG) is very close to 10. Group delay among the MIMO elements is below 2.7 ns, and Channel Capacity Loss CCL is also below 0.4 bits/sec/Hz. Therefore, the proposed 4-element MIMO antenna is suggestible for DSRC/WLAN and X-band applications.