Reflectarray element based on variable line length for millimeter-wave radar applications

Abstract

This paper presents a novel structure of reflectarray element for millimeter-wave reflectarray antennas. The proposed reflectarray element is based on a cut ring patch coupled through an annular slot to a circular patch connected with a variable length line. The reflectarray element is designed for working at 76 GHz. A progressive phase range covering 460 degrees has been achieved by varying the length of microstrip line. The linearity of the reflection phase versus line-length is also reported and improved by modifying parameters of the patches.

Study of Cross-Slotted Circular Microstrip for Reflectarray Design

“…A triple-patch structure loaded with double slots was proven to be able to provide a phase range greater than 360 • [7], but it has many parameters to be optimized. Multilayer microstrip patch unit element structure is another option that is able to introduce reflection phase shift for designing reflectarray [8,9]. In [8], a multilayer unit element with variable slot lengths etched on its ground plane is proven to be able to provide phase range of 330 • ; however, the gradient of the S curve changes too rapidly, making it difficult to be used as a reflectarray element.…”

“…In [8], a multilayer unit element with variable slot lengths etched on its ground plane is proven to be able to provide phase range of 330 • ; however, the gradient of the S curve changes too rapidly, making it difficult to be used as a reflectarray element. An annular slot and a C patch can be combined to design a broad-range reflectarray [9]. Unfortunately, fine tuning such a multilayer structure may not be easy.…”