The demand for higher data transfer rates in the mobile communication networks continues to increase. It is likely that future communication networks will provide increased capacity and performance through the introduction of multiple antennas at both end of the communication link. Multiple antennas offer additional degrees of design freedom that can be used to increase capacity, extend coverage and reduce interference in a wireless network. Employing multiple-input multiple-output (MIMO) antenna systems at both the base stations and in the terminals is thus an effective way to increase capacity.
Increased capacity in MIMO systems requires that the multiple streams of data, which are sent and received in parallel, are independent of each other. In small handheld devices, such as cell phones, the available space for the antennas is very limited and the antenna signals will interact if the antenna implementation is not properly designed.
Compact MIMO antenna systems as in handheld devices not only need to be optimized but also need to find a proper balance between competing requirements such as size and various performance measures. Multi-objective optimization is well suited for this situation, removing the need for upfront weighting of several objectives as commonly used in single objective optimization methodologies. It also reveals the relations between the objectives and builds the basis for overall better decisions.
The Efield® time-domain solver is used to calculate antenna scattering parameters within two frequency bands along with efficiency and signal correlation for two closely spaced planar inverted F-antennas in a handheld device. The layout of the
antennas is controlled by near 25 design variables, which together create a very large design space. The general optimization software modeFRONTIER® is used to automatically search the design space for the optimal antenna layout with respect to firm area constraints and multiple conflicting performance objectives. |
