A more judicious choice of trial functions to implement the Improved Circuit Theory (ICT) application to multi-element antennas is achieved. These new trial functions, based on Tai's modified variational implementation for single element antennas, leads to an ICT implementation applicable to much longer co-planar dipole arrays. The accuracy of the generalized impedance formulas is in good agreement with the method of moments. Moreover, all these generalized formulas including the radiation pattern expressions are all in closed-form. This leads to an ICT implementation which still requires much shorter CPU time and lesser computer storage compared to method of moments. Thus, for co-planar dipole arrays, the proposed implementation presents a relatively very efficient method and would therefore be found useful in applications such as CAD/CAE systems.

This paper describes the characteristics of a one dimensional narrow-wall slotted waveguide array with a single-layer linear-to-circular polarization converter consisting of a dipole array. An external boundary value problem of one slot and three dipoles, which approximates the mutual coupling between the dipole array and an edge slot extending over three faces of a rectangular waveguide, is formulated and analyzed by the method of moments; design of polarization conversion is conducted for this model as a unit element. If every unit element has perfect circular polarization, grating lobes appear in the array pattern due to the alternating slot angle: these are suppressed in this paper by changing the dipole angle and degrading the axial ratio of the unit element. The validity of the design is confirmed by the measurements. The dipole array has negligible effects upon slot impedance; the polarization conversion for existing narrow-wall slotted arrays is realized by add-on dipole array.

A new beam tilt dipole array antenna in a simple structuer has been developed for indoor base stations in the 1.9 GHz band. The antenna comprises a radiator and skewed off-center parasitic elements placed around the radiator. With this stucture, the main beam of the array antenna can be tilted for mobile terminals reception by the effect of mutual coupling. Studies on tilt characteristics for antenna dimensions and tilt mechanism by precise current measurements have clarified the operating principle. The antennas with a fan beam and an omnidirectional pattern have been designed. The measured tilt angle was varied in the range of 0 to 26 with little alteration of the horizontal radiation patterns.