On the Impact of Spillover Losses in 28 GHz Rotman Lens Arrays for 5G Applications

TL;DR

This paper investigates how aberration-induced spillover losses in 28 GHz Rotman lens arrays affect beam focusing and system performance in 5G applications, highlighting the importance of considering these effects in design.

Contribution

It provides a detailed EM simulation-based analysis of aberration effects in 28 GHz Rotman lens arrays, offering insights for improved lens design and system calibration.

Findings

Aberration effects are more severe near array end-fire angles.

Spillover reduces focus accuracy and increases interference.

Results inform better calibration for mmWave lens systems.

Abstract

This work demonstrates the sensitivity of lens antenna arrays operating at millimeter-wave (mmWave) frequencies. Considering a Rotman lens array in receive mode, our investigation focuses on its most imperative defect: aberration of electromagnetic (EM) energy. Aberration leads to spillover of electric fields to neighboring ports, reducing the lens' ability to focus the EM energy to a desired port. With full EM simulations, we design a 28 GHz, 13 beam and 13 array port Rotman lens array to characterize its performance with the aforementioned impairment. Our findings show that the impact of aberration is more pronounced when the beam angles are close to the array end-fire. More critically, the corresponding impact of aberration on the desired signal and interference powers is also investigated for an uplink multiuser cellular system operating at 28 GHz. The presented results can be used as a reference to re-calibrate our expectations for Rotman lens arrays at mmWave frequencies.