A Link Loss Model for the On-Body Propagation Channel for Binaural Hearing Aids

Abstract

Binaural hearing aids communicate with each other through a wireless link for synchronization. A propagation model is needed to estimate the ear-to-ear link loss for such binaural hearing aids. The link loss is a critical parameter in a link budget to decide the sensitivity of the transceiver. In this paper, we have presented a model for the deterministic component of the ear-to-ear link loss. The model takes into account the dominant paths having most of the power of the creeping wave from the transceiver in one ear to the transceiver in other ear and the effect of the protruding part of the outer ear called pinna. Simulations are done to validate the model using in-the-ear (ITE) placement of antennas at 2.45 GHz on two heterogeneous phantoms of different age-group and body size. The model agrees with the simulations. The ear-to-ear link loss between the antennas for the binaural hearing aids in the homogeneous SAM phantom is compared with a heterogeneous phantom. It is found that the absence of the pinna and the lossless shell in the SAM phantom underestimate the link loss. This is verified by the measurements on a phantom where we have included the pinnas fabricated by 3D-printing.

Wearable Shell Antenna for 2.4 GHz Hearing Instruments

“…This was not included in the simulation set-up, where a homogeneous head model is used. This was shown to possibly influence the measured results [5], but as shown below, it is not deemed critical here. The fill liquid in the phantom is targeted to f = 2.4 GHz and is CTIA compliant [25], with nominal electrical properties ε r,SAM = 44 and σ SAM = 2 S/m.…”

Body-Worn Spiral Monopole Antenna for On-Body Communications

“…7 it is seen that the radiation pattern has two lobes, which are in opposite directions. The radiation patterns for other ITE antennas found in [8,12] exhibit the same characteristic, which might indicate that this is a general trend for ITE antennas and is caused by the ear. Furthermore, it is seen that the lobe in the forward direction has the highest gain.…”

“…Therefore, contrary to BTE antennas, it is important to understand how the creeping wave propagates across the face. The previously mentioned E2E on-body path gain models in [8,9], which model the head with elliptic curves, have been tested with antennas where the main path is behind the head. Since the face is not as well modeled with elliptic curves as the back of the head, it is suggested that these models be tested with the main path around the front of the head.…”

“…It has been shown that the electromagnetic energy propagates around the human body as creeping waves instead [7]. Models for the E2E propagation channel have been presented in [8,9] A novel body-worn spiral monopole antenna is presented. The antenna consists of a ground plane and a spiral monopole.…”

In-the-Ear Circular-Shaped Balanced Inverted-A Antenna for Hearing Instruments

“…It has been shown that the energy propagates around the body as creeping waves [9]. Furthermore, it has been shown that the E2E communication channel can be modeled as a number of elliptical paths around the head [10], [11]. In [11] an on-body radiation pattern is introduced and used to estimate the magnitude of the creeping wave launched in different directions.…”