Jani Ollikainen

Coupling element based mobile terminal antenna structures

In this paper, internal low-volume antenna structures for mobile terminals are studied. The work concentrates on the possibilities to reduce the volume of mobile terminal antenna elements by efficiently utilizing the radiation of the currents on the mobile terminal chassis. Essentially nonresonant coupling elements are used to optimally couple to the dominating char- acteristic wavemodes of the chassis. The antenna structures are tuned to resonance with matching circuits. During the last few years, the approach has achieved growing interest—also among industrial manufacturers of mobile terminals. There exist, how- ever, no systematical feasibility and performance studies of the idea. During the work, two antenna models with very low-volume coupling elements are designed and in total four prototypes are constructed. The simulation and measurement results show that the studied antenna concept is a very promising alternative for traditional antenna technologies. The presented analysis provides useful and novel information for the designs of the future low-pro- file and low-volume mobile terminal antennas.

Propagation Between On-Body Antennas

The theory of propagating waves near a surface is reviewed with an eye to gain insight into the mechanisms involved, and to provide analytical-based models, for power-efficient on-body propagation. The Zenneck wave, and in particular the Norton wave, are appraised as candidate mechanisms for the propagation. For flush-mounted (ldquoband aidrdquo) antennas, desired for on-body sensors, the Norton wave is the only direct propagation mechanism between the sensors. The Norton wave fits very well to simulation results presented here, and comparisons are also made with available published physical experiments, although these measurements typically feature the optical paths of elevated, or non-flush, antennas.

Optimal antenna placement for mobile terminals using characteristic mode analysis

When an electrically small antenna element is placed on a small finite ground plane, as in mobile terminals, the ground plane resonances strongly affect the impedance and radiation characteristics of the antenna system. In this paper, we show how characteristic mode analysis can predict the optimal locations of antennas on finite ground planes. As patch-type antennas couple to the ground plane resonances mainly through the electric field, it is natural that the strongest coupling and thus the maximum impedance bandwidth is obtained when the antenna element is placed at the maximum of the electric field of a ground plane mode. This is verified by moving a small probe antenna at selected locations over a rectangular 100 mm by 40 mm ground plane and by computing the obtainable bandwidth at each point.

Removing the effect of antenna matching in isolation analyses using the concept of electromagnetic isolation

Isolation between antennas in a multiantenna terminal plays an important role in the performance analysis of wireless systems. When comparing different methods for increasing isolation between the antennas, it is important to note that isolation depends strongly on antenna matching. The effect of matching on isolation can be removed by numerically matching two antennas simultaneously. The resulting isolation is called electromagnetic isolation and it gives the worst-case isolation between the antennas. An example of the application of this concept to the analysis of ground plane slots is presented. It is shown that the phase information in scattering and impedance matrices is essential to obtain reliable values of the electromagnetic isolation.

Half-Sized Vertical Monopole Ultra-Wideband (UWB) Antennas for Mobile Applications

Compact dual-band and triple-band ultra-wideband (UWB) antennas based on a half-sized monopole for mobile applications are proposed. The antennas are placed vertically at one corner of the ground plane of a mobile terminal. A wider antenna impedance bandwidth is achieved by adjusting the length of the lower edge of the monopole. Details of the proposed antenna as well as simulated and measured results are presented.

Design of HAC compatible mobile phone with LC band-stop filter embedded in PWB

People who have some level of hearing loss normally have to use hearing aids to improve their hearing ability. Digital mobile phones can cause interference to hearing aids because of the electromagnetic (EM) energy emitted by the phones antenna, backlight, GSM burst noise and other components. As required by the FCC, a certain percentage of all sold mobile phone models must be hearing aid compatibility (HAC) compatible. Even though some HAC compliant phones are available on the market, it still requires huge effort in doing so. Therefore, it is quite urgent for mobile phone makers to design HAC compatible mobile phones, in which the strength of the near-field EM fields of the phones reduces to a certain level in the HAC region. According to the FCC requirement, the E-field strength limits for low and high GSM bands are 266.1V/m and 84.1V/m, respectively, whereas the H-field strength limits are 0.804A/m and 0.254A/m. To meet this HAC requirement, approaches for reducing the undesirable effects of the near field EM scattering around the HAC region need to be developed. In particular, a metallization termination technique was used to reduce the EM field scattering at the edge of the printed wring board. A high-impedance thin layer was employed to reduce the EM field scattering at the edge of the PWB. However, these two approaches might cause a reduction of the total radiated power (TRP). In this paper, an alternative way for designing HAC compatible mobile phones is proposed.

Small internal antennas for indoor UMTS base station with WLAN access point

In this paper the use of small internal mobile terminal type of antennas in a typically-sized indoor mobile communication base station is studied. The covered radio systems are 2 GHz UMTS and 2.45 GHz WLAN with diversity path for both thereby leading to four antenna elements placed at the corners of the printed wiring board (PWB). Separate solutions based on a planar loop and a PWB IFA -type of antenna elements are presented with optimal antenna arrangements and orientations. Simulated impedance bandwidths, isolations, radiation properties and estimated envelope correlations are shown. Based on the results, sufficient performances are achievable with both antenna types leading to at least 15 dB isolations and correlations less than 0.1 between the antenna elements. The proposed approach thereby offers a lightweight and a low-cost solution for the application, although the resulting radiation patterns are more irregular compared with a typical sleeve-dipole solution.