Bandwidth investigation of coaxial colinear antennas

Coaxial colinear (CoCo) antennas were considered, for decades, just as being wire antennas. However, the concept of the colinear phased array has been introduced by a number of authors. The principle of dual behaviour (transmission line-cylindrical antenna) allowed a better comprehension of these antennas. We give practical results based both on experimentation and simulation. We first show the technique of impedance calculation (which is the basis of bandwidth evaluation). This depends on frequency, array size, and on the physical parameters of the cables. Finally, we investigate the case of CoCo antennas made of elements with different lengths. (5 pages)