Integrated Four Low-Profile Shorted Patch Dual-Band WLAN MIMO Antennas for Mobile Device Applications

Four dual-band shorted patch antennas (SPAs) with a low profile of 1 mm ( 0.008\lambda at 2.4 GHz) integrated into a square-ring structure of size 66 mm \times66 mm (about 0.53 \lambda \times 0.53\lambda at 2.4 GHz) for 4 \times {4} multiinput-multioutput (MIMO) operation are presented for mobile device applications. Each SPA consists of a larger shorted patch and a smaller shorted patch to, respectively, generate the 2.4 GHz band (2400-2484 MHz) and 5.8 GHz band (5725-5875 MHz) for dual-band wireless local area network (WLAN) operation. Two SPAs are orthogonally connected with the first SPA's larger shorted patch and the second SPA's smaller shorted patch sharing a common metal wall at the corner of the square-ring structure. By repetitively connecting the third SPA to the second one and finally the fourth SPA to the third and first ones, the proposed design can generate four decoupled waves in the 2.4 GHz/5.8 GHz WLAN bands with very low envelope correlation coefficients of less than 0.1. With 1 mm low profile, the proposed WLAN MIMO antennas are expected to find applications in integration with the back cover of the mobile device.