Eigenvalue analysis of phased array element patterns

The sidelobe performance of a phased array antenna is usually assumed to be limited by amplitude and phase errors in the transmit/receive modules or the analog beamformer. However, with a digital beamformer, the signals from the array elements can be combined with arbitrary precision. In that case, the sidelobe performance will be limited by other factors, such as differences in the array element patterns. There is a standard formula for calculating the array sidelobe level due to random errors. The formula assumes that all errors are small, uncorrelated and have a normal, Gaussian probability distribution. Unfortunately, these conditions are not met by the element pattern differences. The eigenvalues of phased array element patterns are examined to determine the sidelobe performance. The average sidelobe level prediction is verified by simulations and measurements.<>