Jorge R. Costa

IEEE Transactions on Antennas and Propagation Announces a Special Issue on “Antennas and Propagation at mm- and sub mm-waves”

Millimeter and sub-millimeter waves have been the focus of intensive research activities over the past several years. Application of these technologies has advanced beyond traditional high-cost niche uses - mostly related to radio astronomy and space applications - to embrace widespread new consumer applications, some of which show significant market potential. Increased opportunity to exploit these bands is in part created by the spectrum availability that enables extremely high data rates and the inherent miniaturizability of the radio front-ends. This naturally drives concomitant advancements in semiconductor technology at mm-waves and sub-millimeter waves that lower technology deployment cost and make it affordable for applications such as home multi-gigabit wireless systems, active and passive high resolution imaging for medical diagnostic or civil security applications, automotive radar, and body-area networks.

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

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.