Considering the non-convexity of hybrid precoding and the hardware constraints of practical systems, a hybrid precoding architecture, which combines limited-resolution overlapped phase shifter networks with lens array, is investigated. The analogy part is a beam selection network composed of overlapped low-resolution phase shifter networks. In particular, in the proposed hybrid precoding algorithm, the analog precoding improves array gain by utilizing the quantization beam alignment method, whereas the digital precoding schemes multiplexing gain by adopting a Wiener Filter precoding scheme with a minimum mean square error criterion. Finally, in the sparse scattering millimeter-wave channel for the uniform linear array, the proposed method is compared with the existing scheme by computer simulation by using the ideal channel state information and the non-ideal channel state information. It is concluded that the proposed scheme performs better in low signal-to-noise regions and can achieve a good compromise between system performance and hardware complexity.

We realize homogenous luminance of the directional backlight for the time-division multiplexing autostereoscopic display using a convex lens array with the elemental lenses whose phase of placement in each row differs from one another. The validity of the proposed optical design is confirmed by a prototype system.

A low-cost technique using commercial UV grade silica fibers to construct microlens array that is suitable for mass-production of long-period gratings is reported. The growth rate of gratings fabricated using these arrays is much faster than the conventional amplitude masks. Our previous work had shown that this technique was 400% more efficient than the metal mask technique. Further improvement of this grating writing technique using plano-convex microlens array is reported in this paper. Under the same writing conditions, long-period gratings with absorption peaks of 1.5 dB and 17 dB were fabricated by using a microlens array and a plano-convex microlens array, respectively.

Monopulse technique is widely used for tracking radars. For tracking at a low elevation angle, a narrow beam is required in the elevation plane to reduce multipath signals such as gound reflections. In this case, an elliptical aperture is desired. We have developed an antenna with a high tracking accuracy and a high aperture efficiency which is composed of a monopulse feed and an elliptical aperture. In this paper we discuss a design of the feed through lens array with an elliptical aperture and a new monopulse feed. Evaluation test results of a production model proved validity of our design and showed good performance.