J. O. Coleman

Experiments in weight design for a sombrero array pattern
K. R. McPhail, J. O. Coleman, and D. P. Scholnik
There is an interest in developing a transmit array taper that illuminates both a highly directive cluster of receive beams and a broad region of the sky at a level that can support a ubiquitous radar function. This report provides experimental optimization results of a sombrero-shaped amplitude array taper that can be used to implement two simultaneous functions of this type. The amplitude tapers are optimized in two ways: boresight radiated power density is fixed while minimizing either max total transmitter power required or max element power required. This report also presents experiments with nonoptimized linear-FM and nonlinear-FM phase-only tapers. The phase-only tapers do improve the peak level loss that occurs in the amplitude optimizations. We do not have the capability to optimize phase-only weights, but intend to give a designer a starting point for exploring phase-only optimization of a sombrero-shaped array factor.
The Fig. 11 design was supposely subject to a 23 dB Taylor-like shelf, but actually the shelf region was not made large enough to properly constrain the inner sidelobes. The shelf began at 6.8 deg but should have been started at something more like 6.3 deg. As a result of this oversight, the inner sidelobe peaks at around 20 dB down.
PDF (13.2 Mbytes),
Published June 25, 2010 as NRL Memo Report 9232. Approved for public release; distribution is unlimited.
August 2010.