Sidelobe reduction for a microstrip travelling-wave antenna array using partially random weighting

The sidelobe performance of a microstrip travelling-wave antenna array is limited by the crosspolarised lobes produced if a comb-line is used with a large range of stub widths.1.2 The amplitude taper which can be applied is thereby limited to ¿6¿7.5 dB, so that very low sidelobes (< ¿30 dB) cannot readily be achieved. Here a technique is described which offers copolar sidelobe reduction without excessive crosspolarisation, with calculated sidelobes <30 dB for a 32-element array. An amplitude taper of 20 dB is achieved using a split comb-line (giving 12¿15 dB taper) plus partially random weighting.