Dirk Manteuffel

Comparisons of computed mobile phone induced SAR in the SAM phantom to that in anatomically correct models of the human head

The specific absorption rates (SAR) determined computationally in the specific anthropomorphic mannequin (SAM) and anatomically correct models of the human head when exposed to a mobile phone model are compared as part of a study organized by IEEE Standards Coordinating Committee 34, Sub-Committee 2, and Working Group 2, and carried out by an international task force comprising 14 government, academic, and industrial research institutions. The detailed study protocol defined the computational head and mobile phone models. The participants used different finite-difference time-domain software and independently positioned the mobile phone and head models in accordance with the protocol. The results show that when the pinna SAR is calculated separately from the head SAR, SAM produced a higher SAR in the head than the anatomically correct head models. Also the larger (adult) head produced a statistically significant higher peak SAR for both the 1- and 10-g averages than did the smaller (child) head for all conditions of frequency and position.

Inductive and capacitive excitation of the characteristic modes of small terminals

In this paper we present concepts for the selective excitation of orthogonal modes of small terminals by inductive and capacitive coupling elements. The concepts can be used to implement an efficient MIMO (Multiple Input Multiple Output) antenna system based on the TCM (Theory of Characteristic Modes). Both coupling concepts are discussed with respect to their ability to excite specific modes separately. An important result obtained is that inductive couplers offer advantages over capacitive couplers in exciting the desired modes purely even when they are not close to their modal resonance.

MIMO antenna design challenges

This paper provides a brief introductions into the challenges involved when designing antenna for MIMO (Multiple Input Multiple Output) systems on small terminals. The investigation is based on the fundamental parameter of cross-correlation of the antenna transfer functions. Some considerations on the correlation of antennas implemented on small terminals are undertaken. It is shown that the correlation of the elements of a multiple antenna system which is implemented on a small terminal is significantly affected by the integration impairments and the platform itself.

Considerations for Reconfigurable Multi-Standard Antennas for Mobile Terminals

Tomorrows mobile terminals shall be multi-standard platforms for various kinds of wireless applications. So far, nowadays mobiles consist of a combination of different separated modules e.g. for GSM, for Bluetooth, WLAN, etc.. Along with these different modules typically separated antennas are use, such as one for GSM/UMTS and another one for Bluetooth and yet another one for FM radio. Currently the design is heading towards multi-standard RF modules that combine several standards or operate on the principle of a software defined radio. Hence, an ubiquitous antenna module that can be attached to such a multi-standard module is required. However, different to the software algorithms and the integrated circuitries, an antenna is still bound to its physical size in terms of wavelength in order to operate efficiently. As the operating frequency of the applications under discussion range from approx. 100 MHz to 2.5 GHz standard antenna concepts for mobile terminals cannot be use because of the large bandwidth and the physical antenna size at low frequencies. The research presented in this paper intends to analyze basic requirements for such an antenna module to operate sufficiently and to propose an applicable concept under the typical constraints of consumer electronic applications and mass production issues.

Optimal Dual-Antenna Design in a Small Terminal Multiantenna System

This letter introduces a novel 2.6-GHz multiple-input-multiple-output (MIMO) antenna system for mobile terminals. The antenna structures consist of a broadband main antenna covering most of the LTE-A bands and a narrowband second antenna operating at the 2.6-GHz band. The main antenna is a traditional monopole-type capacitive coupling element (CCE) placed on the short edge of the terminal. The second antenna consists of two out-of-phase fed inductive coupling elements (ICEs) placed on the long edges of the chassis. The main purpose of the letter is to demonstrate that this kind of antenna system offers good performance in terms of electromagnetic (EM) isolation and envelope correlation between the antennas. This has been experimentally verified and is originated on the fact that both antennas excite effectively different orthogonal wavemodes, which is studied with the help of the theory of characteristic wavemodes.

Numerical analysis of absorption mechanisms for mobile phones with integrated multiband antennas

The absorption mechanism in the human tissue for mobile phones equipped with integrated antennas is analyzed by means of numerical simulations based on the FDTD (finite difference time domain) method. Single-band antennas for 900 MHz and 1800 MHz respectively are situated on realistic models of mobile phones which vary in length. The SAR (specific absorption rate) in a flat-phantom filled with tissue simulating material is observed when the mobiles are situated above. It is shown that there is a strong effect of the PCB (printed circuit board) of the mobile, which acts as the counterpart to the antenna module, on the SAR distribution in the phantom. The investigation shows that especially for 900 MHz the SAR generated by currents on the PCB is dominant in all configurations. Based on the above analysis an integrated multiband antenna for GSM/DCS/PCS is investigated with respect to the SAR distribution in a flat-phantom.

A concept for MIMO antennas on small terminals based on characteristic modes

In this paper, we present a concept for a MIMO antenna system on a small terminal platform. The concept is based on the selective excitation of different orthogonal characteristic modes on the chassis of the small terminal. Thereby the chassis of the mobile terminal itself can be effectively used as the MIMO antenna similar to the concept commonly applied to single port (single mode) antennas on mobile terminals. The different modes generate orthogonal radiation patters and are therefore suited to radiate de-correlated signals fed to the different antenna ports. Such modes can be excited selectively by certain sets of couplers distributed around the outer edges of the chassis. First stage numerical investigations show that coupling between the modes is low.

Highly-efficient multiple antenna-systems for small MIMO devices

In this paper, we focus on highly-efficient multiple antenna-systems for small MIMO communicating devices. First, we perform a state-of-the art review of the best solutions developed by various researchers. Then we consider some fundamental aspects involved when integrating multiple antennas in a small terminal. Thereafter, we present several multiple antenna-systems designed at the LEAT of the University of Nice-Sophia Antipolis since 2004. We especially describe our neutralization technique dedicated to enhance the total efficiency of several radiators when they are closely placed over the same small ground plane. Last, we try to identify promising solutions and future trends.

Efficient characterization of UWB antennas using the FDTD method

In this paper, we present a method for the efficient characterization of UWB antennas based on a combination of FDTD simulation and the Lorentz reciprocity principle. In order to obtain a complete spatio-temporal characterization it is sufficient to determine the transmit transfer function by using first a single numerical simulation of the antenna in transmit mode, in only a small nearfield region, followed by a nearfield to farfield transformation. The application of the Lorentz reciprocity theorem then yields the receive transfer function from the transmit transfer function. The transfer functions of the antenna allows the calculation of all quality measures of interest either in the frequency domain or the time domain. The proposed method is validated by a comparison of its results with an EMPIRE/spl trade/ FDTD simulation of an entire two antenna system.

Norton Surface Waves in the Scope of Body Area Networks

This paper presents an evaluation on how Norton surface waves can be used to analytically model the on-body propagation in wireless body area networks. Based on a brief review of the Norton surface wave theory, the general problem as defined for terrestrial propagation by Sommerfeld, is unified taking into account the further extensions by Norton and Bannister which motivates its evaluation for on-body propagations. A discussion of Sommerfelds numerical distance reveals useful properties to evaluate the capability of a certain configuration to excite Norton surface waves in specific on-body scenarios. Based thereon antenna design guidelines for on-body propagation links can be derived. All investigations are carried out for human muscle, skin, and fat tissues in the frequency range from 0.4 GHz to 60 GHz. A comparison of the simplified model consisting of a planar homogeneous ground to a realistic inhomogeneous human body model shows good results for the attenuation of the electric field strength along the on-body path.