Antenna design tradeoff of multiple antenna terminals with ground plane excitation

It is known that the compactness of mobile terminals complicates the design of multiple antennas, since coupling between the antennas increases when they are placed in proximity of one another. While it is possible to mitigate coupling between closely spaced antennas, a tradeoff in bandwidth is required. In this paper, we highlight ground plane excitation as an additional dimension to consider in the design of multiple antenna terminals. This is because small ground plane can interact with the antenna elements and contribute significantly to their radiation characteristics. In particular, the ground plane effect is important for mobile frequency bands lower than 1 GHz, due to the physical dimensions of today’s mobile terminals. Our results show that several design parameters, namely element locations, spacing between elements, and radiation characteristics of individual elements, must be jointly considered in order to achieve the optimum performance tradeoff for multiple antenna terminals. For example, for a two-antenna setup, even though coupling between the elements can be reduced by decreasing the element spacing to avoid ground plane excitation for one of the antennas, the bandwidth is reduced. (Less)