Beam forming transition based upon a zero-phase-shift metamaterial

摘要

A sector-shaped transmission line along with a zero-phase-shift metamaterial lens has been demonstrated to optimise the coupling between a narrow transmission line connected to the apex of the sector, and a wide transmission line connected to one face of the lens. Throughout the zero-phase-shift metamaterial lens, the phase is constant. One face of the zero-phase-shift lens is connected to, and conforms to, the circular end of the sectoral transmission line, the other face of the zero-phase-shift lens is flat and connects to the wide transmission line. The sectoral transmission line performs impedance transformation, whereas the zero-phaseshift metamaterial lens is a beam former transforming cylindrical waves to plane waves. The flare angle can be large thereby reducing the length of the transition, and the device can be used in compact multiway power dividers. Both spatial and frequency response calculations of a transition with a 90u000b0; flare angle, and operating at 1 GHz, show that a pure transverse electromagnetic (TEM) wave is excited in the wide transmission line with negligible transverse variation in both amplitude and phase, compared to considerable transverse variation without the lens. At 1 GHz the input reflection coefficient was 28.7 dB compared to 26.9 dB without the lens, and 22.5 dB using a slab of the zero-phase-shift metamaterial in place of the lens.