Antenna design and channel modeling in the BAN context—part I: antennas

Abstract

The first results achieved in the French ANR (National Research Agency) project BANET (Body Area NEtwork and Technologies) are presented (Part I). This project mainly deals with the antenna design in the context of Body Area Networks applications and channel characterization. General conclusions are drawn on the body impact on the antenna performance for onon and in-on communications (Medical Implant Communication Systems). Narrow-band and ultra-wideband contexts are addressed both numerically and experimentally, and it is shown that design questions are significantly different for each case, leading to different constraints and guidelines. For narrow-band antennas, an alternative and original approach of desensitization using ferrite sheets is proposed and compared to classical techniques based on ground-plane screening. The characterization of numerical phantoms is also analyzed with narrow-band canonical antennas. For the specific on-on scenario, morphologies and electrical properties of the human tissues are also included in the topics of interest. For ultra-wideband antennas, focus is put on planar balanced designs, notably to reduce harmful "cable effects" occurring during the antenna characterization or the channel sounding. For both types of antennas, the main parameter under study is the distance to the body, which has a significant influence.

Multislot Antenna with a Screening Backplane for UWB WBAN Applications

“…For example, in Table 2 the variations of the radiation efficiency are 8%, 13%, and 16% at 3.5, 4.5, and 5.5 GHz, respectively, for the reference MSA, whereas for the MSA-BP the variations are only 4, 0 and 8% at 3.5, 4.5, and 5.5 GHz, respectively. The MSA-BP is almost insensitive to the distance between the radiation layer and the phantom, which is an important concern for antennas used in WBANs [13].…”

“…However, although very compact (with a height of 10 mm), its main drawback is that it is "protruding," and consequently restricted to an integration in rather thick devices. In addition, extra losses caused by power absorption of the human body, as well as diffraction and reflection effects due to its high permittivity, degrades the antenna overall total efficiency and radiation characteristics [13][14][15]. These physical phenomena have of course a significant negative impact on the radio link performance.…”

“…For narrowband (NB) antennas, input matching is of major concern, as detuning is the main effect (the matching frequency decreasing as the antenna/body spacing is reduced). Indeed, irrespective of other effects such as losses or increased directivity, the strong influence of the body in the antenna reactive zone [13,16,17,19,20] can lead to a collapse of the energy transfer because of an abrupt increase of the reflection coefficient. Consequently, for NB antennas, resorting to desensitization techniques with respect to the body proximity is mandatory.…”

An UWB Coplanar Waveguide Fed Integrated IFA Design for Wearable Communications

“…The above-mentioned body proximity effects still exist for UWB antennas, but their bandwidth is so wide that the possible detuning effects appear somehow more "globally" regarding the matching over the BW of interest (although for multi-resonant antennas each resonance can be affected). Therefore, possible abrupt radio link outage due to the collapse of the total efficiency which often occurs for narrow band antennas in the vicinity of a human body (when the detuning is such that the mismatch becomes extremely severe) is generally avoided for UWB antennas [7].…”

“…This antenna achieves a 10 dB bandwidth of about 20 % around 2.045 GHz. In [9], a general design of a wideband CPW-fed IIFA, based on a design proposed in [7], is presented. The shorted end and open end horizontal strips being close enough to the CPW ground plane "patches", their coupling is strong and they can be viewed as asymmetrical coplanar strip (ACPS) [10].…”