Miniaturization of 4×4 Butler matrix using high slow-wave factor structure

In this paper, a novel slow-wave structure with high slow-wave factor is proposed. The new structure composed of meandered-line structure, low-impedance transmission line and interdigital structure is capable of reducing the circuit size significantly due to its good slow-wave property. A miniaturized 4×4 Butler matrix resonant at 970MHz is designed using the proposed structure. The size of the proposed 4×4 Butler matrix is merely 5.8% of the conventional ones. The measured results of the manufactured are in good agreement with the simulated results.