Phase-Delay Versus Phase-Rotation Cells for Circular Polarization Transmit Arrays—Application to Satellite Ka-Band Beam Steering

Parinaz Naseri,Jorge R Costa,Carlos A Fernandes,Sergio A Matos

doi:10.1109/tap.2017.2787540

Abstract

Planar transmit arrays (TAs) have been an attractive solution as gain enhancers for various applications, e.g., satellite communications. The TA performance directly depends on its composing unit-cell characteristics. Planar unit cells can be categorized into two main types: phase-rotation (PR) and phase-delay (PD) cells. There is no hint in the literature about the relative merits of these two types of cells for circular polarization when assessing the final TA performance. This paper offers a systematic comparison between the cells' working principles and analyzes their impacts on TA performance. Examples of a PR-based TA and a PD-based TA are designed for single-band wide-angle beam steering operating at the satellite Ka-band. They are evaluated by simulation and measurement to quantify performance differences. No previous work employed a PR TA for wide-angle beam steering. This paper shows that PR TA offers a filtering effect toward the cross-polarization component of the source. This leads to better axial ratio and combined 3 dB axial ratio and 3 dB gain bandwidth. However, PD cells are easier to design and insensitive to feed polarization. The analysis in this paper allows a more informed decision when selecting the unit-cell category for any given TA application.

Highlights

TRANSMIT-ARRAYS (TA) have been an attractive solution to achieve high-gain pencil-beam in many applications such as point-to-point links and satellite communications due to their potential low-weight, moderateprofile, low-cost, high efficiency, simple feed network, and no feed blockage effect [1]
In order to verify the aforementioned comparisons between the two types of cells, the two TAs presented in Fig. 9 were fabricated
It is shown that the phase rotation (PR) unitcells are twice of the size of the phase delay (PD) cells while they only have 1⁄3 of the PD cells’ thickness

Summary

Introduction

TRANSMIT-ARRAYS (TA) have been an attractive solution to achieve high-gain pencil-beam in many applications such as point-to-point links and satellite communications due to their potential low-weight, moderateprofile, low-cost, high efficiency, simple feed network, and no feed blockage effect [1]. The working principle of a TA is similar to the one of a dielectric lens [2] in which each zone of the lens or TA adds an appropriate phase shift to the field passing through it. This is met by adjusting the lens profile, in a TA, this is achieved by adjusting each phase shift provided by individual unit-cells with constant thickness populating the TA. The unit-cells should have minimum reflection and minimum insertion loss, while ensuring a phase shift range up to 360 ̊ in order to correct the phase of the incident wave at each point of the TA surface. The amount of phase shift required for a cell is dependent on the desired phase of the outgoing wave at cell position of the TA minus the phase shift that the incident wave endures from the feed until it reaches that cell position

Results

Discussion

Conclusion