Dual-Band Butler Matrix with the Same Phase Difference for Long-Term Evolution Applications

Abstract

ABSTRACTA novel dual-band Butler matrix is proposed with the same phase difference, aiming at the interest of long-term evolution. The total circuit simply includes four 3-dB 90° dual-band couplers and two 45° broadband phase shifters, which are capable of operating at two separate frequencies. Due to the utilized 45° broadband phase shifter, the phase differences remain invariant at two unrelated frequencies between the adjacent outputs. This Butler matrix can be easily fabricated by using single-layer microstrip technology. The measured results of a prototype demonstrate that it can operate at both 1.85 and 2.7 GHz, which perform phase errors and coupling ratios within 5.44° and –6.63 ± 0.72 dB.