Design, realisation and evaluation of a liquid hollow torso phantom appropriate for wearable antenna assessment

Abstract

This study examines the design, realisation and evaluation of a lightweight and low cost hollow oval cross‐section torso phantom appropriate for wearable antenna performance assessment. The phantom consists of an empty inner space (hollow) surrounded by a shell with double plastic walls between which there is a tissue simulating liquid. The phantom's plastic shell is made of a low loss cast acrylic and the liquid is a commercially available one with properties calibrated for the frequency range of 2–6 GHz. The proposed phantom is compared, through simulations, with a full liquid torso phantom and a heterogeneous anthropomorphic voxel phantom. In addition, the fabricated phantom is compared with human bodies and a homogeneous anthropomorphic solid phantom, through measurements. The phantom performance is tested in terms of electric field distribution of a wearable antenna on its surface and the path loss between two wearable antennas, on either side of the phantom. It is proved that the hollow phantom performance approximates the full liquid phantom when an RF absorbing material is placed in the central hollow region. The phantom performance in terms of S11 wearable antenna measurements is evaluated and found in good agreement with real human bodies in the examined frequency range (2–6 GHz). The far‐field wearable antenna performance of the proposed phantom shows deviation in gain <1.5 dB, compared with anthropomorphic phantom.

Human Exposure to Emfs From Wearable Textile Patch Antennas: Experimental Evaluation of the Ground-Plane Effect

“…The physical and electrical properties of components that simulate biological organs were tabulated by Gabriel [30] through parametric modeling and can be obtained automatically thanks to the on-line application prepared by the Italian National Research Council [31]. These properties are achieved through a wide range of human tissue-equivalent mixtures, which are housed by enclosures that can be found in literature [32][33][34][35][36] and in market [5,6]. The mixtures [32][33][34] are usually classified according to the number of tissue-layers (homogeneous: 1 tissue layer, heterogeneous: multiple tissue layers), base ingredient, and low/high-water content (e.g., liquid, gel, semi-solid, solid), etc., whereas containers ([5, 6, 32, 35, 36]) are classified according to their resemblance to the external envelope of the human body shape (e.g., anthropomorphic or physical models, canonical models), etc.…”

“…The dimensions of the internal volume of the phantom enclosure have been decided to equal the average dimensions of an adult torso, that is to say: 33 cm × 14 cm × 49 cm [36]. The enclosure is made of Plexiglass (ε r = 2.36, tan δ = 1.62 * 10 −3 , thickness = 6 mm).…”

Lessons Learned about the Design and Active Characterization of On-Body Antennas in the 2.4 GHz Frequency Band

“…The characterization of BSN antennas is normally addressed without taking into account the effects of the transceiver itself and the consideration of a finite ground plane, which can greatly influence the antenna performance [28]. All of these, combined with the fact that the propagation mechanisms through the human body are not unknown in enough detail, underline the need for more exhaustive studies that analyze the influence of the human body on antennas and viceversa, to be undertaken [29].…”

“…The passive measurement inside an anechoic chamber is the standard method for the experimental characterization of antennas [8,21,27,29,30]. However, this method may be unsuitable if the characterization of the antenna integrated in a self-powered electronic device is required, given that the hardware components also influence the radiation characteristics [23,31].…”

“…Phantom to emulate on-body condition (separated): In this case, the space between the antenna and the metal support was occupied by a phantom of biological material to emulate the presence of the human body. Containers of liquids or gels that simulate the electrical properties of the body tissues have been used [29], but in this work a biological material of similar structure (skin, fat and muscle) is proposed. A chicken for food consumption was selected to implement the phantom (2.45 kg, clean inside, featherless at room temperature), which was fixed to the support.…”