Ivan Bonev

Characterization of the Indoor Multiantenna Body-to-Body Radio Channel

In this paper, we investigate the wideband body-to-body radio channel with multiple antennas at both ends based on a time-domain radio channel measurement campaign. Four single-element transmitters and eight quad-element receivers were mounted on three test people. Both directional and omnidirectional antennas have been investigated. A comparison between electromagnetic antenna simulations and the measurements shows that the multipath environment reduces the body losses effectively. Channel characterizations in terms of path loss, body shadowing, small-scale fading, and spatial correlation have been derived. Small path-loss exponents (< 2.0) are observed in the investigated environments. Considerable power loss due to body blockage makes the body shadowing a prominent factor in the short-range body-to-body communications. Distributed antenna selection diversity is presented to mitigate the body shadowing. A 5-dB diversity gain in the average received power at the mean and 10% outage levels have been identified based on the measurements with two distributed antennas mounted on the transmitter and receiver person and without channel-state information feedback to the transmitter.

User Influence on MIMO Channel Capacity for Handsets in Data Mode Operation

The current paper concerns realistic evaluation of the capacity of the MIMO channel between a BS and handheld device, such as a PDA or smartphone, held in front of the users body (data mode). The work is based on measurements of the MIMO channel between two widely separated BSs in a micro-cellular setup, and six handsets located in an indoor environment. The measurements are done simultaneously in both the 773.5-778.5 MHz and 2250-2350 MHz bands, and from the two BSs. The handsets are realistic types and were measured both in free space and with twelve different users, using both one and two hands. The random capacities of the channels are evaluated in terms of outage capacity. For an SNR of 10 dB, median capacities in free space of about 4.4-4.7 bit/s/Hz for the low band and about 3.3-3.8 bit/s/Hz for the high band were found. The mean decrease in outage capacity due to the user was found to be up to about 2.2 bit/s/Hz, depending on the band and handset. More results are presented in the paper.

A modified metamaterial inspired antenna solution for reduction of the Specific Absorption Rate in the head

In this paper, we present a design of a metamaterial inspired inverted F antenna (MIIFA) mounted on a ground plane with form factor corresponding to a typical candy bar type of mobile phone. The presented design is compared with a conventional inverted F antenna (IFA) in terms of an averaged Specific Absorption Rate (SAR) values in the head. The SAR has been evaluated as it is described in the standard but also the influence of the hand on the SAR has been demonstrated. The proposed MIIFA has decreased SAR values in the head by close to 40 % compared to the conventional design.

Broadband investigation of the spatial correlation of antennas for mobile phones

In this paper the correlation coefficient between two inverted L-antennas (ILA) in wide frequency range is investigated. The coefficient has been calculated by using expression in terms of far-field radiation patterns in the azimuth plane. Novel theoretical expressions are obtained for this coefficient in the case of a couple of parallel short horizontal dipoles in a uniform angle of arrival (AoA) distribution. Moreover, the numerical simulations for the correlation coefficient obtained for two ILA antennas are compared to the correlations developed for two short vertical and horizontal dipoles. Good agreement between analytical results for generic antennas and simulation results for two real ILA antennas is found.

Investigation of multi-antenna mobile terminals in terms of hearing aids compatibility

In this paper, we present an investigation of the near fields (NF) of different configurations of two antennas mobile phones with a candy bar phone factor. The study has been carried out via Finite Difference Time Domain (FDTD) simulations. Interesting paradigms not valid for the single antennas have been identified. In order to obtain a hearing aids compatible (HAC) mobile phone having two antennas, special attention has to be focused on the NF at the high band as opposed to the single antenna case where the HAC is defined by the NF at the low band.

A novel solution for decoupling of two closely spaced antennas at low frequencies

In this paper, we present a novel technique to increase the isolation between two very closely spaced planar inverted F antennas (PIFA) on a common ground-plane. The proposed decoupling structure consists of thin wire (TW) array and two Z elements. For the proposed antenna at low band, the improved isolation between the antennas is from 3.1 dB (for the initial PIFA) to 10.8 dB. Further, the proposed technique has been proven to be efficient in the presence of the user.