||An antenna miniaturization technique that can substantially miniaturize an antenna to allow its incorporation into a compact package for WLAN (2.4–2.484 GHz) applications is proposed. For this purpose, the semiconductor-based glass integrated passive device (GIPD) manufacturing technology is adopted. To facilitate the design, an equivalent circuit approach is applied to the loop-based antenna in which the structure is conveniently integrated with the ground trace in the semiconductor fabrication process to improve both miniaturization and radiation efficiency. Under these conditions, the resonant length of the loop antenna is not necessarily one-wavelength so the antenna can be made electrically small. This approach was extended to construct a multiple-input-multiple-output (MIMO) antenna in a small IPD. The gap between the driven strip and the loop structure functions as an internal tuning circuit, thus contributing to antenna miniaturization. Moreover, the multiple antenna elements are arranged to construct a MIMO system. Furthermore, a good isolation (S21 < −15 dB) is achieved using a space of only 0.3 mm (0.005 λ) spacing between two antennas.|
In addition, isolation enhancement between two closely spaced antennas was achieved based on the reaction theorem. A MIMO antenna consists of radiation elements and a ground plane that were located on the top and bottom side of the substrate, respectively. In order to generate an equivalent magnetic current source, a slot was set on the ground nearby the transmission line. Then, the electric fields cross the slot so that it generates an equivalent magnetic current source to diminish the effect caused by the coupling electric current source, resulting in a lower magnitude of the S21. Single, dual and wideband antenna applications were demonstrated.