Compact Four-Port Antenna Suitable for Portable MIMO Devices

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 lambda_o times 0.33 lambda_o 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.