On the design of low sidelobe microstrip arrays

The author discusses the results of a study of the factors that affect the sidelobe level of arrays, concentrating on those factors that are of critical importance for microstrip arrays. The validity of the author´s conclusions is demonstrated with the design of a 16-element linear microstrip array that achieved a measured sidelobe level of -35 dB or -19 dBi. The factors considered are feed network amplitude and phase accuracies, feed network radiation, effect of narrow patch bandwidth on phase accuracy, mutual coupling, element positioning errors, errors due to imperfect element match and feed network isolation, and diffraction effects. By examining the variances for each of the factors listed considered, it was easy to identify those which are primarily responsible for a poor sidelobe performance. In the present example, the most important factor was the frequency trimming of the antenna elements.<>