Generation of Patterns From Concentric Ring Arrays With Dipoles and Waveguides

Introduction

The conventional antennas are used for radar and communication applications. The ring arrays are used for angular symmetry applications (Ma, 1974). The patterns are synthesized with isotropic radiators in concentric ring arrays for generation of desired directional patterns. The resultant radiation patterns depend on the array factor and element pattern. But, in the case of isotropic radiator, the element pattern is unity. Hence, the resultant pattern is the same as the array factor. In this work, directional characteristics are evaluated for the ring arrays and concentric ring arrays with practical radiators.

Various types of practical radiating elements are used in arrays to achieve the desired directional characteristics. The commonly used practical radiating elements are dipoles, monopoles, waveguides, horns, slots and micostrips patch antennas etc. They are used depending on the applications (Ma, 1974, Elliott, 1981; Raju, 2005; Haupt, 2010). Dipole radiators are preferred in low range of frequencies. Half-wave dipoles find wide applications particularly in communications and radars. Dipole length is consider as , spacing between the elements is consider as , and all the elements are excited with uniform amplitude distribution, because grating lobes can be eliminated and mutual coupling is minimized. One of the most suitable elements for phased array antenna is the open-ended rectangular waveguide. Waveguides are useful at microwave range of frequencies. Waveguides are used to guide electromagnetic waves from point to point. However, these elements have very different scan characteristics in the E and H planes. Spacing between the elements is considered as , because mutual coupling is reduced, and grating lobes can be eliminated.

Knudsen (1956) has proposed ring arrays. The elements of the ring arrays are not perpendicular, but the dipoles are placed as in ring geometry. The dipoles are placed normal/tangential to the ring array. The synthesis and analysis of very larger circular array (Hussain et al., 1987) is reported deterministic manner to optimization of the pattern. Space tapered thinned array (Steyskal, 1970) are considered to produce a desired power pattern with the design and implementation a procedure for optimization. Royer (1966) has investigated ring arrays properties as (i) in the horizontal field patterns the serration to be small (ii) the mean horizontal directive gains greater than that of the monopoles from the array. The antenna impedance and mean directive gain of the ring array is also found.

Ring arrays (Redlich, 1970) are designed for aircraft navigation. Synthesizing a ring array in the plane, radiation pattern is developed. The optimum design of ring minimum diameter and minimum number of radiators of specific location in the plane.