Soft Surfaces for Reducing Mutual Coupling Between Loaded PIFA Antennas

The use of planar soft surfaces to reduce mutual coupling in a new type of planar inverted-F antenna (PIFA) is demonstrated in this work. The proposed antenna is dual-band, single-port, and quite compact, especially for the low frequency of operation. At that frequency band, the mutual coupling is more critical. With the purpose of decreasing this coupling, a solution based on soft surfaces made of simple printed strips with grounded vias is presented, achieving a simultaneous reduction on the mutual coupling level at the two bands of operation of the antenna. In this particular example, only two strips are used and a reduction on the coupling of more than 6 dB is experimentally verified for these two bands and for different distances between elements. The use of a multilayer substrate is a key aspect in the proposed design.