M字形誘電体アレー構造による広帯域移相器

抄録

This paper proposes a new design procedure and structure of a wideband dielectric phase shifter for mobile base stations. Phase shifters are used to tilt the main beam direction of a base station antenna array in the elevation angle. Recently, to enhance communication capacity for accommodating increasing data traffics due to the increased number of smartphones and tablets, multiple frequency bands were added in mobile communication systems. Therefore, wideband phase shifters are demanded. The proposed phase shifter composes two arrayed M-shaped dielectrics to introduce a periodic dielectric structure. This structure enhances a frequency bandwidth by creating a lower resonant frequency. Because resonant frequencies and bandwidth of the proposed phase shifter can be adjusted by using a design equation of the M-shaped dielectric phase shifter, the proposed method can simplify a wideband phase shifter design. Frequency responses of voltage standing wave ratio (VSWR) less than 1.2 were theoretically analyzed, satisfying a frequency range from 1.4 to 2.2GHz. This range covers 1.5, 1.7, and 2.2GHz band, where this phase shifter is designed to obtain a phase shift of 60 deg. at the center frequency, 1.8GHz. A prototype of the proposed phase shifter was fabricated to validate the frequency responses of VSWR less than 1.2. The experimental result confirmed that the proposed phase shifter can approximately realize the objective bandwidth.