SURFACE WAVE BEHAVIOR IN PHASED ARRAYS
Abstract
Mutual coupling in a phased array can cause its radiation performance to vary with electrical phasing used to steer the array. Large performance degradations can accrue when many coupling contributions add in-phase. This happens when the steering phase advance equals the mutual coupling phase delay between consecutive elements. For these critical scan directions reflections can be very large, and the antenna array will transmit or receive very little power, as evidenced by deep holes in the element radiation pattern. A large, flat, uniformly spaced array of identical antenna elements is analyzed. A relationship is found between critical scan angle and mutual coupling coefficients. Element radiation pattern, active array mismatch, and radiation efficiency are shown to be equivalent representations of phased array scan performance. Extensive radiation pattern and mutual coupling measurement were made in a planar, equiangular array of coaxial horn antennas. These measured mutual coupling coefficients were summed over columns of the test array. The phases of these column sums were found to vary linearly with distance. At the critical scan angle, all columns on one side of the array couple in-phase and re-radiate destructively, causing deep holes in array coverage and in element radiation pattern. Empirical coupling velocities were less than the free space velocity of light. Radiation holes appeared at scan angles which were smaller than those for which the grating lobe maximum enters real space. Many physical perturbations of the array geometry were investigated experimentally to determine their influence on array scan performance.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1966
- Accession Number
- AD0804590
Entities
People
- Lawrence W. Lechtreck
Organizations
- Sylvania Electric Products