Implementation of an antenna array on a 5G mobile phone chassis is crucial in ensuring the radio link quality, especially at the millimeter-waves. However, we generally lack the ability to design antennas under practical operational conditions involving body effects of a mobile user in a repeatable manner. We developed numerical and physical phantoms of a human body for evaluation of mobile handset antennas at 28 GHz. While the numerical human model retains a realistic and accurate body shape, our physical phantom has a much simpler hexagonal cross section to represent a body. Gains of the phased antenna array configuration on a mobile phone chassis, called colocated array is numerically and experimentally evaluated. The array is formed by placing two sets of 4-element dual-polarized patch antenna arrays, called two modules, at two locations of a mobile phone chassis. Modules are intended to collect the maximum amount of energy to the single transceiver chain. Spherical coverage of the realized gain by the array shows that the experimental statistics of the realized gains across entire solid angles agree with numerical simulations. We thereby demonstrate that our antenna evaluation method reproduces the reality and our phantom serves repeatable tests of antenna array prototypes at 28 GHz.

Penetration of cellphones into markets requires their robust operation in time-varying radio environments, especially for millimeter-wave communications. Hands and fingers of a human cause significant changes in the physical environments of cellphones, which influence the communication qualities to a large extent. In this paper, Referential cellphone antenna arrays at 28 and 39 GHz are designed, and then simplified electromagnetic models of them for simulations are developed. Their radiation properties are evaluated through near-field scanning of the two prototypes in free space, first for de-embedding the feedline loss of cellphone antennas. The similarity of radiation patterns between simplified models and cellphone mock-ups ensures the reliability for comparing simulated and measured results involving real-hand effects. Next, hand-antenna-interaction radiation measurements are set up so that we validate radiation performance simulations that use computational models of real hands that are generated by the approach in [1] and cellphones, by carrying out measurements of the same real hands and cellphone mock-ups and comparing measured to simulated results, which we show to agree well. This enables future research and development of mm-wave handset antennas relying on realistic simulations during the design phase.

The emergence of mobile terminals operating at millimeter-wave 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 letter 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 a two-hand mode.

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 multi-layered 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 paper, 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 frequency range 1, 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.

Under-sampled arrays exhibit low mutual coupling, alleviating heat dissipation challenges associated with active radio frequency (RF) components in integrated front-end designs. This paper presents an effective dielectric dome lens (DDL) for a uniform array with one-wavelength inter-element spacing, enabling beam scanning with reduced grating lobes, making it suitable for millimeter-wave communication systems. The shape of the DDL is optimized using the geometric optics (GO) algorithm, allowing for the reflection of grating lobes while maintaining effective main beam scanning. The DDL is then miniaturized, integrated with absorber sheets to dissipate reflected grating lobes, and equipped with matching layers to improve radiation performance. The subsequent full-wave simulation further optimizes the design, accounting for factors overlooked by the GO algorithm and finalizing the DDL structure for operating with a under-sampled array. Finally, a 3 × 8 under-sampled rectangular patch array working at 28 GHz, integrated with a cylinder DDL, is fabricated and measured to validate the design approach. The experimental results are in agreement with the simulations. With the help of the DDL, the array with one-wavelength inter-element spacing achieves a continuous, symmetrical-to-boresight beam-scanning range of 110°, with a scan loss (SL) within 3 dB. The grating lobe is consistently reduced, maintaining peak side-lobe levels more than 9 dB below the main beam. This scanning performance remains effective over a bandwidth of 2 GHz.

An analytical model for an antenna-embedded wall, also called signal-transmissive wall, is presented in this work. In the signal-transmissive wall, multiple antenna elements are distributed periodically on both wall sides, and connected back-to-back through coaxial cables. Numerical full-wave simulations of the signal-transmissive wall are computationally demanding due to the fine meshes required in the cables while having an electrically large wall size. Therefore the simulations above 8 GHz are not feasible even with a powerful cluster computer of the authors’ research site. The analytical model is an attractive alternative to the full-wave simulation of the wall, which combines the individual transmission characteristics of the bare wall, realized gains of antenna elements and cable losses. The analytical model accurately reproduces the full-wave simulated transmission coefficient of the signal-transmissive wall up to 8 GHz for arbitrary polarizations and incident angles of a plane wave. The model therefore allows analyses of the signal-transmissive wall beyond 8 GHz, showing more than 70 dB reduction of the transmission loss at 30 GHz compared to a bare wall.