Cherry and Iskander [196,197] have used the FDTD method to model an array of interstitial antennas for hyperthermia purposes. In 1994, Ren et al. [198] analyzed 2-D phased-array antennas with Floquet boundary conditions. Also in 1994, Thiele and Taflove [199] presented results for the radiation from Vivaldi flared horn antennas and arrays, while Naito et al. [200] presented results for a single radiator of a circularly polarized printed array composed of strips and slots. Uehara and Kagoshima [201] have recently analyzed microstrip phased-array antennas.