Element Pattern of an Axial Dipole in a Cylindrical Phased Array. Part 1. Theory. Part 2. Element Design and Experiments. Volume 1

摘要

Cylindrical array antennas are attractive for applications requiring uniform 360 azimuthal pattern performance. For very low sidelobe or precise angle measurement designs, an accurate knowledge of the mutually coupled element pattern becomes important. In Part 1 of this report, 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 approaches 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. In Part 2, the design and construction of a cylindrical array of axial dipoles is described. Dipole-pattern amplitude measurements performed over practical scan and frequency ranges show excellent agreement with theoretically predicted results. Dipole pattern phase, feed-line effects, and radiator match are also discussed. These results provide strong evidence of the correctness of the analysis and numerical results presented in Part 1 and furnish a firm basis for accurate prediction of array performance.