Antennas based on modified metallic photonic bandgap structures consisting of capacitively loaded wires

Antenna systems based on some improved metallic photonic bandgap (MPBG) structures are introduced. A useful modification is introduced by replacing each wire in a two-dimensional MPBG structure by a chain of many identical conducting elements of a certain shape. Each such chain forms an effective wire of capacitive impedance. The optimal design for maximal radiation efficiency and directivity is obtained by choosing an appropriate value of the impedance per unit length for the effective wire and the geometry of the modified MPBG structure. The optimal impedance is realized by using elements of various shapes, including broken wire elements and planar H-shaped elements. Numerical results have shown that the modification can increase the efficiency of the MPGB antenna by a factor of 1000, as well as reduce the thickness of the MPGB structure to about lambda / 3 in the presence of a metal background plane. (C) 2001 John Wiley & Sons, Inc.