Electric field distributions around the human body with a small antenna in the frequency range of 2.5 MHz to 2.5 GHz

Abstract

In recent years, body-centric wireless communications become an active area of research due to their various applications such as e-healthcare, support systems for specialized occupations, and personal communications. Since the candidate frequencies for body-centric wireless communications widely range from MHz to GHz, dielectric properties of the human body tissues, relative dimensions of the human body to wavelength, and the propagation channels around the body extremely vary with frequencies. In this paper, to bring objective and unified idea on the frequency characteristics of body-centric wireless communication channels, electric field distributions around the human body wearing a small antenna in a wide frequency range of 2.5 MHz to 2.5 GHz are numerically calculated. The results show that behavior of the electric field distributions around the human body could be broadly divided into two ranges; below 100 MHz and above 250 MHz. I TRODUCTIOIn recent years, body-centric wireless communications become an active area of research due to their various applications such as e-healthcare, support systems for specialized occupations, and personal communications [1-7]. Since the candidate frequencies for body-centric wireless communications widely range from MHz to GHz, dielectric properties of the human body tissues, relative dimensions of the human body to wavelength, and the propagation channels around the human body extremely vary with frequencies. Therefore, we have to focus on certain frequency bands in most cases. For example, in a frequency range below several MHz, of which wavelength is longer than the human body, the physical propagation mechanism is unclear yet; thus, the electromagnetic phenomena are often explained by using lumped-parameter equivalent circuit that the devices and the human body are electrostatically coupled [2]. However, an equivalent circuit is sometimes not enough, and upper limit of frequency that such explanation is capable is still unclear. In this paper, to bring objective and unified idea on the frequency characteristics of body-centric wireless communication channels, electric field distributions around the human body wearing a small antenna in a wide frequency range of 2.5 MHz to 2.5 GHz are numerically calculated. These data would be useful to choose appropriate frequency range for specific applications. UMERICAL MODELI G OF A TE A A D HUMA BODYSince extremely wide frequency range is used in this calculation, an antenna should remain as simple and identical as possible over the range. From this requirement, a typical top-loaded monopole antenna shown in Fig. 1 is used. The antenna has low-profile dimension (5 mm thick) and has no matching structure (e.g. shorting posts); thus, impedance matching is not considered here. However, its radiation pattern is omnidirectional for any frequency over the range. Moreover, its ground plane partially simulates an electrode mounted to HF-band devices. Fig. 2 shows a whole-body block model with the antenna. The model has homogenous dielectric...

Frequency dependence of on-body channels with top-loaded monopole antennas in the range of HF to UHF

“…Lastly the levels at the ears are relatively stable; however, one deep null is found at 300 MHz when the model is raising the hand. Incidentally, we have already confirmed that the presence of the earth ground has little effect on the channels [6].…”

“…In recent years, body-centric wireless communications have become an active area of research due to their various applications such as e-healthcare, support systems for specialized occupations, and personal communications [1]- [6]. Whereas UHF bands are subjects of interest especially in Europe, relatively low frequency bands below several megahertz are also in researchers' and corporations' interest especially in Japan [4], [5].…”

“…So, we believe that 3-D EM simulations are important to assess the channels accurately. In our previous paper, we calculated the electric field distributions around a human body wearing a small top-loaded monopole antenna in a wide frequency range (3 MHz-3 GHz) to bring objective and unified idea on the frequency characteristics of body-centric wireless communication channels [6]. In this paper, we numerically observe the open voltage of receiving antennas as a gauge, and examined three different postures.…”

A Study of Factors Affecting Wrist Channel Characteristics for Walking Postures Using Motion Capture

“…Further information on 3D character animation using motion capture can be found in [17]. C. Avatar Tissue Material Following the work of [6], [7], [18], an homogeneous tissue value of 2/3 that of muscle ( r = 35 and = 1.16 S/m) was used for the avatar and validated by S 21 measurement at 2.45 GHz. The simulation used the parameters in Table I where the inclusion of a concrete floor was found to be necessary when antennas were mounted below the waist.…”