Investigation of low-profile fresnel zone plate antennas

This article presents low-profile configurations of the Fresnel zone plate antenna at Ka-band. The investigation involved progressively reducing the focal distance of the antenna through simulations and observing the effect on the directivity, radiation patterns, and aperture efficiency. The number of metal zones was also varied in the simulations. It was found that focal distances below 0.75λ yielded little more directivity than the feed itself. With a single zone, the 1.25λ focal distance achieved the highest overall aperture efficiency of 24%, which was a significant improvement over the larger focal distance cases. Measurements were performed to verify the simulated results

Fresnel zone plate antenna with hexagonal-cut zones

A novel Fresnel zone plate antenna (FZPA) with hexagonal-cut zones is presented. This new structure was simulated at 30 GHz using a finite-difference time-domain software to study its gain and sidelobe levels in relation to the standard circular FZPA and the hexagonal FZPA. Several prototypes were built and tested to verify the simulations. It was found that the FZPA with rotated alternating hexagonal-cut zones provides the ability to control the shape and location of the sidelobes while still maintaining the benefits of the hexagonal shape in terms of array packing. Also, this new structure has an improved sidelobe level over the standard version

Hexagonal Fresnel zone plate antenna

A novel hexagonal Fresnel zone plate antenna is introduced and compared to the traditional circular Fresnel zone plate antenna. The comparison was carried out in simulation by using a finite-difference time-domain software. Although the circular lens performs better, the hexagonal geometry is better suited for arrays and provides the ability to both improve the sidelobe level and shift the sidelobe location away from boresight. This is accomplished by appropriately rotating the rings that make up the lens and is achieved without sacrificing directivity or 3dB beamwidth

A systematic study of varying reference phase in the design of circular fresnel zone plate antennas

A circular Fresnel zone plate antenna was simulated using a finite difference time domain software to study the effect of changing the reference phase from the standard 0° to any value between 0° and 180°. Several prototypes were built to validate the simulations using four different focal-length-to-diameter (F/D) ratios. It was found that a significant improvement in the level of the first sidelobe, up to about 9 dB according to the simulations, could be achieved without sacrificing gain or cross-polarization levels

More Precise Shaping of Guide Screws with Trapezoidal Thread

© 2020, Allerton Press, Inc. Abstract: How does the thread-cutter configuration with respect to the workpiece axis in roughing affect the shape precision of the external trapezoidal thread and the margin in final grinding? That question is investigated in the present work. An algorithm is outlined for determining the transverse profile of the helical channel in the external trapezoidal thread at the inner, central, and outer diameters. The channel profile calculated from that algorithm determines the cutting-edge profile at the front surface of a cutter positioned perpendicularly to the part’s helical surface for preliminary machining