Vanja Plicanic

Actual Diversity Performance of a Multiband Diversity Antenna With Hand and Head Effects

Using the metric actual diversity gain (ADG), diversity performance is investigated for a compact mobile terminal prototype with two internal, triple frequency band antennas in four different cases of user interaction. ADG is presented as a preferred alternative to apparent diversity gain and effective diversity gain. Absorption due to user proximity causes degradation and imbalance in mean effective gain of the antennas over the frequency bands, contributing to a degradation in diversity performance. However, user-induced changes in the antenna patterns cause a decrease in correlation in the low frequency band, which facilitates increased diversity gain. The study reveals that a significant net diversity gain, i.e., ADG of 5-8 dB compared to a single antenna prototype, can be achieved using multiband antennas in the proximity of a user, even at low frequencies for antennas with high mutual coupling.

A Compact Six-Port Dielectric Resonator Antenna Array: MIMO Channel Measurements and Performance Analysis

MIMO systems ideally achieve linear capacity gain proportional to the number of antennas. However, the compactness of terminal devices limits the number of spatial degrees of freedom (DOFs) in such systems, which motivates efficient antenna design techniques to exploit all available DOFs. In this contribution, we present a compact six-port dielectric resonator antenna (DRA) array which utilizes spatial, polarization and angle diversities. To evaluate the proposed DRA array, a measurement campaign was conducted at 2.65 GHz in indoor office scenarios for four 6 × 6 multiple antenna systems. Compared to the reference system of monopole arrays which only exploit spatial diversity, the use of dual-polarized patch antennas at the transmitter enriches the channels DOF in the non-line-of-sight scenario. Replacing the monopole array at the receiver with the DRA array that has a 95% smaller ground plane, the 10% outage capacity evaluated at 10 dB reference signal-to-noise ratio becomes equivalent to that of the reference system, due to the DRAs rich diversity characteristics. In the line-of-sight scenario, the DRA array gives a higher DOF than the monopole array as the receive counterpart to the transmit patch array. However, the outage capacity is 1.5 bits/s/Hz lower, due to the DRA arrays lower channel gain.

Diversity antenna terminal evaluation

Simulated and measured correlation and diversity performance for a couple of two-antenna concepts are presented. The results indicate that the three-dimensional isotropic incident field is a good reference case to evaluate diversity performance in a multi-antenna application.

Performance of Handheld MIMO Terminals in Noise- and Interference-Limited Urban Macrocellular Scenarios

Multiple-antenna handheld terminals are an integral part of the latest mobile communication systems, due to the adoption of multiple-input multiple-output (MIMO) technology. In this contribution, MIMO performances of three multiple-antenna configurations for smart phones are investigated in an urban macrocellular environment, based on an extensive MIMO measurement campaign at 2.65 GHz. The smart phones were held in a two-hand user grip position and both downlink noise- and interference-limited scenarios were evaluated. Our results show that, overall along the test route, the capacity performances are dictated by the power of the communication links. Nevertheless, locally, the multipath richness of the communication channel can have a significant impact on the capacity performances. In addition to the terminal antenna configurations, spatial and cross polarization references were also utilized to further illustrate the importance of multipath richness in both the desired and the interference channels. Moreover, the differences in the local capacity performances along the route for the three antenna configurations give a first indication of the potential benefit in implementing reconfigurable multiple antennas. If switching for maximum capacity is applied between the terminal antenna configurations in the two-hand grip position, average capacity improvements of up to 17% and 30% for local 20 m route sections are observed in the noise- and the interference-limited scenarios, respectively.

Antenna diversity evaluation for mobile terminals

In this paper we are focusing on the practical, engineering way of evaluating and characterizing the multi-channel antenna solutions on the mobile terminal. Two methods of calculating the parameters, describing the diversity performance, are described and the practical use of the methods in simulations and measurements are presented and evaluated. The time saving aspect of using the scattering parameters is lifted forward but also its limitations. For comparison, a statistical method for calculating diversity gain is also presented. This evaluation is performed for two multi-channel antenna solutions with different characteristics for the purpose of characterizing different diversity performances.

Impact of Antenna Design on MIMO Performance for Compact Terminals With Adaptive Impedance Matching

Using the metrics of channel capacity and multiplexing efficiency, the adaptive impedance matching (AIM) performances of two multiple-input multiple-output (MIMO) terminals with different antenna designs were evaluated and compared. The evaluation was performed in LTE Band 18 Downlink (860-875 MHz) under realistic usage conditions of two measured user handgrips and simulated propagation channels with different angular spreads (ASs). The results provide potential performance gains from AIM based on realistic MIMO terminal prototypes, and the underlying mechanisms by which the gains were achieved, which can serve as antenna and AIM circuit design guidelines. In particular, the evaluation revealed that ideal uncoupled AIM networks can increase the capacity by up to 52% relative to 50-Ω terminations. However, the observed gains depend heavily on the antenna design, the user scenario, and the channels AS. For example, the wideband design in different user cases experienced capacity gain of 4%-9% from AIM in uniform 3-D channels, in contrast to the 1.3%-44% gain seen in a conventional narrowband design. In nonuniform channels with small ASs, the AIM gain for different mean incident angles depends on the absolute mean effective gain (MEG) and the change in correlation due to AIM; in cases where AIM has little impact on correlation, the mean incident angles with high AIM gains were close to those with high MEGs.

Assessment and Modelling of Terminal Antenna Systems

The pervasive use and insatiable demand for high-performance wireless devices globally are driving the development of new communication technologies and standards. In this chapter, we present advancements in the area of terminal antenna systems and describe how they play a major role in enabling strict performance requirements to be met in future systems. As opposed to conventional systems that do not require explicit considerations of the terminal antenna beyond the satisfaction of some predefined design criteria in impedance bandwidth, radiation pattern and efficiency, multiple antenna systems in upcoming and future wireless networks must deliver significantly higher performance goals.

Diversity mechanisms and MIMO throughput performance of a compact six-port dielectric resonator antenna array

This paper demonstrates multiple-input-multiple-output (MIMO) throughput performance of a six-port dielectric resonator antenna (DRA) array for Wireless-LAN applications in a measured indoor office environment when a six-port dual-polarized patch array is used at the transmitter. The throughput was obtained using an IEEE802.11n/Draft 5.00 simulator for measured channels with different antenna and propagation setups. The throughput performance of the patch-DRA array set-up is found to be similar to that of a set-up with six-port monopole arrays at the receive and transmit ends in the non-line-of sight (NLOS) environment. The compact design of the DRA array causes lower port efficiencies relative to those of the monopole array, notwithstanding the compact DRA array is shown in this paper to effectively utilize angle, polarization and spatial diversity mechanisms to achieve comparable throughput performance.

Experimental Investigation of Adaptive Impedance Matching for a MIMO Terminal With CMOS-SOI Tuners

It is well known that user proximity introduces absorption and impedance mismatch losses (MLs) that severely degrade multiple-input multiple-output (MIMO) performance of handset antennas. In this work, we experimentally verified the potential of adaptive impedance matching (AIM) to mitigate user interaction effects and identified the main AIM gain mechanism in realistic systems. A practical setup including custom-designed CMOS silicon-on-insulator (SOI) impedance tuners implemented on a MIMO handset was measured in three propagation environments and ten real user scenarios. The results indicate that AIM can improve MIMO capacity by up to 42% equivalent to 3.5 dB of multiplexing efficiency (ME) gain. Taking into account the measured losses of 1 dB in the integrated tuners, the maximum net ME gain is 2.5 dB suggesting applicability in practical systems. Variations in ME gains of up to 1.5 dB for different hand-grip styles were mainly due to differences in impedance mismatch and tuner loss distribution. The study also confirmed earlier results on the significant differences in mismatch and absorption between phantoms and real users in which the phantoms underestimated user effects and, therefore, AIM gains. Finally, propagation environments of different angular spreads were found to give only minor ME gain variations.

Experimental study of adaptive impedance matching in an indoor environment

In recent years, adaptive impedance matching (AIM) has been used to compensate for severe performance degradation in terminal antennas due to user proximity. In particular, user effect compensation is critical for multiple-input multiple-output (MIMO) terminals, to achieve high data rates. In this study, the AIM performance of a MIMO terminal is measured for three user scenarios at two locations in an indoor office environment, using real impedance tuners. It was established that AIM leads to MIMO capacity gains of up to 25%, corresponding to 2.2 dB of power gain. On the other hand, the insertion loss of the tuners was found to be about 0.3 dB for free-space conditions. These results suggest that AIM can offer significant net performance gains in practice. Moreover, we provide physical insight into the similar AIM results for the two measured locations, representing geometrical line-of-sight (LOS) and non-LOS links, respectively.