SYNTHESIS OF THE VARIABLE SHAPE CONTOURED DIRECTIVITY PATTERNS OF THEHYBRID REFLECTOR ANTENNAS

To reduce the number of driven elements in a broadside colinear antenn a array, in narrowband applications COCO (coaxial colinear) antennas h ave been used since relatively recently, either as isolated elements, or as parts of antenna arrays. COCO antennas have a single actual port , but the driving voltage is transmitted to several other ports via tr ansposed segments of a coaxial cable of which the antenna is made, res ulting in approximately cophasal currents along the COCO antenna segme nts. This paper is aimed at demonstrating that COCO antennas are a spe cial case of a new wide class of one-port, multiply-excited antennas ( ''OPOMEX'' antennas), which can be in a variety of forms, including pr inted versions. The design of OPOMEX antennas is significantly more fl exible than that of COCO antennas, since they have more parameters tha t in practical realizations can be varied easily. The paper describes two approximate methods for the analysis of OPOMEX antennas, and prese nts numerical and experimental results for a number of such printed-st rip antennas. Numerical results are found to be in reasonable agreemen t with experiment.