Element pattern of an axial dipole in a cylindrical phased array, Part I: Theory

Cylindrical array antennas are attractive for applications requiring uniform azimuthal pattern performance. For very low sidelobe or precise angle measurement designs, an accurate knowledge of the mutually coupled element pattern becomes important. A modal solution is presented for an element pattern in a periodic array of axial dipole radiators placed coaxially over a circular cylindrical ground. This solution avoids the problems associated with asymptotic appproaches and displays a number of advantages: 1) it is exact, subject only to truncation errors; 2) it is uniformly valid in all spatial regions for both rectangular and, with a simple modification, for triangular isosceles lattice configurations; and 3) it provides absolute gain information. The analysis is presented along with numerical results for representative parameter values, selected to illustrate the various trade-offs. Comparison with published data employing the asymptotic approach and with planar array results is given.