A compact PIFA suitable for du...

A compact PIFA suitable for dual-frequency 900 1800-MHz operation596

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 46, NO. 4, APRIL 1998

where d is the minimum distance from the source to the scan sphere, t0 is the starting time for the electromagnetic eld that is radiated from the source, and fn (!ns a=c) = 0; s = 1; 1 1 1 ; n. By using the denitions of fn (z ) and gn (z ) and the expressions for the multipole ~ tan (~ coefcients (2) it can be shown that E r ; t) is indeed real. Since the outputs of perfect electric and magnetic dipoles are proportional to the time derivatives of the incident electromagnetic and magnetic elds in the direction of the electric and magnetic dipole moment, one can, by using such probes, immediately nd the coefcients (@=@t)anm (t) and (@=@t)bnm (t) needed in (3) and, consequently, avoid a numerical evaluation of the