Additively Manufactured Broadband Miniaturized Quadrature Coupler and Its Application to 2-D Scanning Broadband Butler Matrix

Abstract

This article presents a broadband miniaturization quadrature coupler with good amplitude and phase performance and its application to a 2-D scanning broadband Butler matrix. The coupler comprises two stages of coupled-line couplers and two T-type networks. Cascaded coupled-line couplers achieve wide matching bandwidth. T-type networks achieve good amplitude and phase imbalance performance. The broadband miniaturization coupler is applied to a $4\times 4$ 2-D scanning broadband Butler matrix. The coupler and Butler matrix are realized using the additively manufactured electronics (AMEs) technique. The sizes of the coupler and Butler matrix are $0.078\times 0.057\times 0.0058\lambda _{\mathbf {0}}$ and $0.13\times 0.074\times 0.0086\lambda _{\mathbf {0}}$ , respectively, where $\lambda _{\mathbf {0}}$ indicates the free space wavelength at the center frequency. Within $0.6\sim 1.4$ GHz, the measured return loss of coupler exceeds 16.8 dB, and the isolation is better than 19.3 dB. The amplitude and phase imbalances of the coupler are better than 0.34 dB and 2°, respectively. Within $0.6\sim 1.4$ GHz, the measured return loss of Butler matrix exceeds 16.5 dB, and the isolation is better than 15.5 dB. The amplitude and phase imbalances of the coupler are better than 1.8 dB and 7.2°, respectively.