Passive Antenna Systems Embedded into a Load Bearing Wall for Improved Radio Transparency

Abstract

Providing cellular network services inside residential or office buildings has become challenging, especially for fifth-generation networks that use higher carrier frequencies. Additionally, new energy-efficient buildings contain envelopes such as low-emissivity glass and new multi-layer thermal insulations, all of which -unintendedly but effectively -also block radio signals. As a solution to those problems of indoor coverage, we suggest the use of passive antenna systems embedded into the building walls. We propose a numerical evaluation method for determining the electromagnetic transmission coefficient and the thermal insulation of a typical building wall. Next, we investigate two antenna configurations embedded to the wall, a two-patch and a four-patch design, both operating around 3.5 GHz. We show from numerical simulations that those antenna systems increase the transmission coefficient of the wall. At the same time, we show that the four-patch design does not compromise the thermal insulation of the wall.

Analytical Characterization of a Transmission Loss of an Antenna-Embedded Wall

“…The signal transmissive wall consists of multiple components like a wall, antenna elements, and coaxial cables. In this manuscript, we continue working on the same bare load-bearing wall as used in our previous works [7]- [10] as illustrated in Fig. 1(a).…”

“…The signal-transmissive wall can be made using numerous types of antenna elements, in this manuscript, we use antenna elements presented in [7], [8]. The first one is a spiral antenna element, which is designed to avoid detuning effects due to concrete using a foam backing as shown in [8].…”

“…The second antenna system is the patch antenna system presented in [7] where two patch antennas are connected back-to-back by a single coaxial cable. To satisfy thermal insulation regulation given by the Finnish government [6], the size of the cable is reduced and the conductor material is changed to stainless steel compared to the original design in [7]. The coaxial cable center conductor diameter is 0.92 mm, the dielectric diameter is 3.17 mm and the thickness of the shield is 0.2 mm.…”

“…In previous works of the authors [7]- [10] we introduced an antenna embedded wall called a signal-transmissive wall where passive antenna elements were embedded back-to-back to a load bearing concrete sandwich wall. Numerical full-wave simulation models of the signal-transmissive wall were verified against experiments up to 8 GHz radio frequency.…”

5G to 6G: A Paradigm Shift in Radio Channel Modeling

“…However, numerical evidence of those conjectures is still very limited, let alone experimental verification. The use of reconfigurable meta-surfaces (see below) and integration of waveguiding and relaying antenna arrays into building walls (Vähä-Savo et al, 2021) are possible ways to expand coverage beyond the present reach and may change the co/adjacent channel interference conditions completely.…”