**BECAUSE OF MAIN-BEAM SCANNING**, assessing the performance of a phased-array antenna usually involves the repeated calculation of its far field. Unfortunately, the time-consuming brute-force method comprises the calculation followed by the summation of a large number of complex exponentials, which represent the individual contributions of the array elements to the far field. For an array antenna populated by 1000 array elements, calculating that far field would be on the order of minutes. As an alternative, a computer program dubbed APAS (for Advanced Phased-Array Simulator) has been presented by Will P.M.N. Keizer from The Netherlands.

This simulator promises to provide both accurate and high-speed computation of the far-field patterns of planar phased antennas including advanced far-field analysis capabilities and comprehensive two-dimensional (2D) and three-dimensional (3D) visualization of the simulated results. The program was written in MATLAB from The MathWorks. To minimize execution time, it is coded as matrix operations. Two-dimensional Fast Fourier Transform (FFT) techniques are used to calculate the far-field patterns.

With this software, it is possible to synthesize user-defined, low-sidelobe tapers for both the sum and difference patterns of arrays. APAS can handle aperture configurations with the array elements sited along rectangular or triangular lattices. In addition, the aperture may consist of subarrays. The program allows the noise figure and third-order intercept point of both the array and applied-transmitting/ receiving module to be calculated. See "APAS: An Advanced Phased-Array Simulator," *IEEE Antennas And Propagation*, April 2010, p. 40. For a demonstration version of the software, contact willkeizer@ieee.org.