It has been shown that shaped dipole antennas tend to have higher directivity
as compared to those of straight dipole (Landstorfer and Sacher, 1986 and Petkovic
and Krstic, 2002). The Nu-dipole which is the varying act of the
V-dipole (one among the types of shaped dipole) has only its lower arm taking the shape of an arc (Okereke, 1999).
Series of programs have been written and improved upon for the analysis of
linear antenna arbitrarily shaped, mostly using Method of Moment (MOM). In Kuo and
Strait (1972) a program was written in Fortran for the analysis of radiation and
scattering of arbitrarily thin bent wires using matrix methods.
Okereke (1999) analyzed a single Nu-dipole antenna for input admittance
and input power, and compared the results with that of a V-dipole. In a
related development, analysis of the characteristics of six-element Yagi-Uda antenna array
of Nu-dipole element was carried out by Okereke (2007) for maximum directive
gain. In Liang and Cheng (1983), length, shape and position of a symmetrical
three-element Yagi-Uda array of shaped dipoles were optimized to maximize the arrays directive
gain. MOM was used to convert the integro-differential equation into a matrix form
after which a simplex matrix technique was used to obtain the current distribution on
the array. In order to apply the MOM, each array element was divided into 22
segments that are equal in their projected length along the x-axis (horizontal axis).
Using constant radius and length of 0.01l and 1.5 l, a directive gain of 11.8 db was obtained. Gain optimization for 10-element Yagi-Uda arrays was done by Cheng
(1991) using a three-term approximation for the driven element and two-terms with
complex coefficient for the parasitic elements for integral-equation formulation. |
