Optimizing a large array configuration to minimize the sidelobes

Abstract
A new method of minimizing sidelobes of a large array whose element spacing is much larger than the wavelength has been developed. The analytical expression for the first derivative of the array beam with respect to the element shift of the array is obtained. Using this expression, it is possible to minimize the value of a beam pattern for a given direction. The minimization of the array's worst sidelobe is carried out iteratively. At each iteration, the worst sidelobe found is suppressed. A task in the National Radio Astronomy Observatory (NRAO) astronomical image processing system (AIPS) was written to apply the optimization algorithm. This task provides the optimization of the array's element position and plots the initial and optimized configurations. The optimization can be carried out under the following constraints: doughnut, two circumferences, topography, and minimum spacing between the array elements. Another constraint can be added. The area of the sidelobes' minimizing is the circle in the sky with the center at the main beam.

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