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A method of analyzing Yagi-Uda-type antennas is presented. Since the Yagi-Uda array is a fairly well-known antenna, it is used as an example to demonstrate the application and accuracy of the method. However, the method of solution is not limited to a planar array, such as the Yagi, but can be applied to arrays of nonplanar linear elements. The approach taken in analyzing Yagi-Uda antennas is based on rigorous equations for the electric field radiated by the elements in the array. All interactions are taken into account. Calculated results are presented for the Yagi-Uda array that show excellent agreement with experimental results reported in the literature. In addition, the dependence of the far-field patterns on the phase velocity is shown. It is also demonstrated that the phase velocity is generally nonuniform along the array.

Abstrucl-An iterative method is developed for computing the scattered electric fields at the apertures of large perfectly conducting cavities. The field iterative method (FIM) uses KirchhofPs approximation to initiate a two stage iterative process (i.e., the method of successive approximations), involving both the magnetic field integral equation and the electric field integral equation, to calculate the electric currents on the internal cavity walls and the electric fields across the aperture of the cavity. The technique combines the flexibility of the boundary-integral method with the speed necessary to efficiently analyze large scale cavity problems. The following paper presents the general theory, and applies the technique to the problem of TE scattering from two-dimensional perfectly conducting cavities.

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