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In this letter, a compact four-port antenna structure with an area of 40 times 40 mm2 and constructed from inexpensive FR-4 printed circuit board is described. The antennas operate at 2.48 GHz, and in terms of wavelengths have a compact overall area of 0.33 lambdao times 0.33 lambdao and this would usually result in very strong mutual coupling between the four antenna ports. However, in our proposed structure, the mutual coupling between antenna elements is better than -10 dB. Although this is not low mutual coupling by some standards it is suitable for multiple-input-multiple-output (MIMO) communications in portable devices as verified by our experimental MIMO testbed capacity results. Furthermore measurements and characteristics of the antenna structures are provided.