Electromagnetic-Thermal Analyses of Distributed Antennas Embedded into a Load-Bearing Wall

Abstract

The importance of indoor mobile connectivity has increased during the last years, especially during the Covid-19 pandemic. In contrast, new energy-efficient buildings contain structures like low-emissive windows and multilayered thermal insulations which all block radio signals effectively. To solve this problem with indoor connectivity, we study passive antenna systems embedded in walls of low-energy buildings. We provide analytical models of a load-bearing wall along with numerical and empirical evaluations of wideband back-to-back spiral antenna system in terms of electromagnetic- and thermal insulation. The antenna systems are optimized to operate well when embedded into load-bearing walls. Unit cell models of the antenna-embedded load-bearing wall, which are called signal-transmissive walls in this article, are developed to analyze their electromagnetic and thermal insulation properties. We show that our signal-transmissive wall improves the electromagnetic transmission compared to a raw load-bearing wall over a wide bandwidth of 2.6-8 GHz, covering most of the cellular new radio (NR) frequency range 1 (FR1), without compromising the thermal insulation capability of the wall demanded by the building regulation. Optimized antenna deployment is shown with 22 dB improvement in electromagnetic transmission through the load-bearing wall.