Miniaturisation of switched beam array antenna using phase delay properties of CSRR‐loaded transmission line

Abstract

The application of phase delay property of complementary split-ring resonator (CSRR)-loaded transmission line in the miniaturisation of Butler matrix beam forming network is proposed. The design of left-handed transmission line and the influence of the capacitive stubs in the phase delay properties of the CSRR-loaded transmission line with a gap are presented. The CSRR-loaded transmission line with a 7 mm capacitive stub provides 93° more phase delay than the CSRR-loaded transmission line without the stubs. CSRR-loaded transmission line with capacitive stubs is applied to the phase compensating lines of 4 × 4 Butler matrix configurations, without disturbing the 90° hybrids and crossovers. The CSRR-loaded configuration exhibits a size reduction of 48% of the footprint of the conventional Butler matrix. The output of the miniaturised Butler matrix is connected to a linear microstrip antenna array of four radiating elements and its radiation parameters (beam pointing direction, beamwidth and sidelobe levels) are compared with that of an unloaded conventional 4 × 4 Butler matrix. The miniaturised switched beam-steering antenna exhibits similar radiation characteristics as that of a conventional switched beam antenna.