A novel modularized folded highly compact LTCC Butler matrix

This paper describes the realization of a 8x8 Butler matrix taking full advantage of the 3D packaging capability of LTCC. The novelty of the design lies in the folding and stacking of phase shifters and couplers on 40 layers of LTCC tape to reduce the lateral dimensions of a 5GHz Butler matrix. The achieved size reduction is better than 1/5 of the original planar design showing excellent electrical performance. Furthermore, the new LTCC realization allows modular extension of Butler matrices to multiples of 8x8.