Antennas based on modified metallic photonic bandgap structures consistingof capacitively loaded wires

Antenna systems based on some improved metallic photonic bandgap (MPBG) str uctures are introduced. A useful modification is introduced by replacing ea ch wire in a two-dimensional MPBG structure by a chain of many identical co nducting elements of a certain shape. Each such chain forms an effective wi re of capacitive impedance. The optimal design for maximal radiation effici ency and directivity is obtained by choosing an appropriate value of the im pedance per unit length for the effective wire and the geometry of the modi fied MPBG structure. The optimal impedance is realized by using elements of various shapes, including broken wire elements and planar H-shaped element s. Numerical results have shown that the modification can increase the effi ciency of the MPGB antenna by a factor of 1000, as well as reduce the thick ness of the MPGB structure to about lambda / 3 in the presence of a metal b ackground plane. (C) 2001 John Wiley & Sons, Inc.