A Compact, Wide Field-of-View Gradient-index Lens Antenna for Millimeter-wave MIMO on Mobile Devices

Lens-based beam-forming antennas offer a low-power, low-cost alternative to hybrid beamforming antenna arrays. They are ideally suited to millimeter-wave massive MIMO systems due to their native beam-space operation and angular selectivity and minimal dependence of high-speed data converters. We discuss the design of a compact and low-cost lens-based beam-forming antenna for small form-factor platforms such as small-cells and mobile devices in 5G wireless networks. We discuss a gradient-index design method and low-cost fabrication method based on perforated dielectrics. We discuss the need for high-contrast permittivity ranges to achieve wide scan angles which are essential for leveraging the full capability of massive MIMO systems (e.g., full stream capacity). Finally, we show that by using an appropriately designed perforated medium, gradient-index lenses with low minimum permittivity of 1.25 can achieve a maximum beam-steering angle of 44 degrees. We suggest that such an approach can enable practical low-loss, low-cost, and compact beam-steering lens antennas for millimeter-wave MIMO with wide beam-steering angles.Comment: To be presented September 24-27 at the Fall 2017 Vehicular Technologies Conference (http://ieeevtc.org/vtc2017fall/) in the "5G Millimeter-Wave Channel Measurement, Models, and Systems" trac

High-efficiency, Wideband GRIN Lenses with Intrinsically Matched Unit-cells

We present an automated design procedure for the rapid realization of wideband millimeter-wave lens antennas. The design method is based upon the creation of a library of matched unit-cells which comprise wideband impedance matching sections on either side of a phase-delaying core section. The phase accumulation and impedance match of each unit-cell is characterized over frequency and incident angle. The lens is divided into rings, each of which is assigned an optimal unit-cell based on incident angle and required local phase correction given that the lens must collimate the incident wavefront. A unit-cell library for a given realizable permittivity range, lens thickness, and unit-cell stack-up can be used to design a wide variety of flat wideband lenses for various diameters, feed elements, and focal distances. A demonstration GRIN lens antenna is designed, fabricated, and measured in both far-field and near-field chambers. The antenna functions as intended from 14 GHz to 40 GHz and is therefore suitable for all proposed 5G MMW bands, Ku- and Ka-band fixed satellite services. The use of intrinsically matched unit-cells results in aperture efficiency ranging from 31% to 72% over the 2.9:1 bandwidth which is the highest aperture efficiency demonstrated across such a wide operating band.Comment: Submitted for review on October 14, 2019 to IEEE Trans. on Antennas and Propagation, Revised on March 14, 202