Wideband 3-D Printed All-Metal Reflectarray With Notches for Low-Cost Millimeter-Wave Applications

In this paper, a 3-D printed all-metal reflectarray is presented for millimeter-wave applications. The array has sub-wavelength element spacing, so that the elements are non-resonant. A two-stage notch is etched at the top of the element, which provides multiple degrees of freedom for phase tuning. The phase variation range is more than 360° by changing the height and width of the first stage of the notch. Thanks to the non-resonant property and the two-stage notching, stable phase shift can be maintained in wide frequency range. A reflectarray with $20\times 20$ elements is fabricated by using 3-D printing technique, which has the merits of flexible construction, light weight and low cost. The simulated and measured results on radiation patterns and realized gain are highly consistent. The measured 1-dB gain bandwidth achieves 17.6%, ranging from 31 GHz to 37 GHz. In the whole 1-dB gain bandwidth, the measured aperture efficiency is higher than 47.7%, with a peak efficiency of 53.6% at 31 GHz. The proposed reflectarray has no substrate loss and can provide high aperture efficiency in wide bandwidth.