Coupled tapered slot-line antenna with sum/difference beams

The tapered slot-line antenna (TSA) has been investigated for decades, There are increasing applications of TSA for integrated phased arrays developed in recent years, which require both wide bandwidth and wide scanning angle. Though the TSA element in the array has been developed for three basic types, they are little used as an independent antenna. Recently, a Twin Vivaldi antenna fed by coplanar waveguide (CPW) was reported mainly for integrating with active devices; it also provides centred zeros in E-plane with low cross-polarisation. The authors had proposed a novel type coupled tapered slot-line antenna (CTSA), which forms simultaneous sum/difference beams and reduces the sidelobe-level in H-plane. The numerical analysis of CTSA has been completed, then its optimization design based on genetic algorithm developed, and the experimental samples accompanying sum/difference beam forming circuit were analysed. In this paper, the scheme of design and measurement of the sum/difference duplexer of CTSA with balun and transition are presented, the results show that for the desired simultaneous sum/difference beams, the best null-depth of the difference-beam is below -30.2dB. This CTSA is suitable for replacing the traditional horn for a monopulse radar system as a printed feed with less aperture blockage.