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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.

The 5th generation (5G) cellular networks offer high speeds, low latency, and greater capacity, but they face greater penetration loss through buildings than 4G due to their higher frequency bands. To reduce this loss in energy-efficient buildings, a passive antenna system was developed and integrated into sandwich walls. However, the thermal effects of this system, which includes highly thermally conductive metals, require further study. In this research, three-dimensional heat transfer simulations were performed using COMSOL Multiphysics to determine the thermal transmittances (U-values) of 5G antenna walls. The results revealed that, using stainless steel as the connector material (current design), the U-value rose from 0.1496 (for the wall without antenna) to 0.156 W/m2K, leading to an additional heating loss per year of only 0.545 KWh/m2 in Helsinki. In contrast, with the previous design that used copper as the connector material, the U-value increased dramatically to 0.3 W/m2K, exceeding the National Building Code of Finland’s limit of 0.17 W/m2K and causing 12.8 KWh/m2 additional heat loss (23.5 times more than the current design). The current design significantly reduces thermal bridging effects. Additionally, three analytical methods were used to calculate antenna wall U-values: parallel paths, isothermal planes, and ISO 6946 combined. The isothermal planes method was found to be more accurate and reliable. The study also found that a wall unit cell with a single developed 5G antenna and a wall consisting of nine such cells arranged in a 3 × 3 grid pattern had the same U-values. Furthermore, areas affected by thermal bridging were typically smaller than the dimensions of a wall unit cell (150 mm × 150 mm).

The emergence of mobile terminals operating at millimeter-wave (mmWave) frequencies necessitates the ability to evaluate the effect the environment and, in particular, users have on their radiation properties. Some studies evaluated the shadowing effects of a hand or an entire body for simple antenna configurations. This manuscript proposes a method for reliably predicting the performance of different array geometries in the presence of the users when they operate the mobile with one or with two hands. In practice, the way a mobile is operated is varying strongly between users and hence it is of great interest to draw a methodology to both numerically and experimentally evaluate any handset design in a large number of use cases in a repeatable manner. The use of numerical models and realistic phantoms allow high repeatability when evaluating the terminal radiation under real use conditions. Both the simulated body and the human phantom are used to study the field scattering from the handset arrays subject to the user interaction, yielding consistent results between them. Results suggest that shadowing by the user's torso usually decreases gain between 20-30 dB close to the region of the user. The user posture largely affects the spherical coverage, particularly for those antennas close to the corners in two-hand mode.