Gerald Artner

Effect of carbon-fiber composites as ground plane material on antenna performance

The impact of carbon fiber composites (CFC) as a ground plane material on antenna performance is investigated. CFC are lightweight materials that, due to their high mechanical durability, are increasingly used as chassis material for cars. Their electrical characteristics are anisotropic and dependent on the manufactured structure, which is expected to influence the radiation pattern. Simple monopole antennas for 2.45GHz (ISM) and 5.9GHz (ITS G5) are mounted to circular ground planes made of three different CFC and aluminum sheets. The influence on antenna performance is investigated with calibrated gain, return loss and the radiation pattern measurements.

Carbon fiber reinforced polymer integrated antenna module

Rising demand for vehicular communication and cooperative movement have led to an increase of vehicle mounted antennas. A carbon fiber reinforced polymer cavity is presented, that can be integrated into the vehicle chassis. The concealed cavity is large enough to house the anticipated antennas for present and future vehicular communication. Influence of the cavity onto antennas is demonstrated with calibrated gain measurements on the example of a 5.9GHz monopole antenna for intelligent transportation systems. The cavities impact on antenna performance is found to be much smaller than influences of the car itself.

Measuring the impact of outdated channel state information in interference alignment techniques

Interference alignment has been proposed as a transmission technique to cancel the interference for the K-user interference channel at high signal-to-noise ratio. In the case of multiple-input multiple-output (MIMO)-transmission the interference can be aligned in a subspace of the receiver antennas. In this work we investigate the impact of outdated channel state information (CSI) due to temporal channel variations on the performance of interference alignment. Experimental transmissions of real-time precoded signals from an indoor and outdoor MIMO testbed exhibit performance degradation due to outdated CSI. Furthermore, a model is proposed and evaluated that describes the temporal channel fluctuations based on these measurements.

Material induced changes of antenna performance in vehicular applications

Recent advancements in production materials for cars replace well-known ground plane materials for vehicular antennas. Carbon-fiber composites (CFCs) replace steel as chassis material, which leads to reduced radiation efficiency. As the production processes of shark-fin antenna modules shift towards laser direct structuring (LDS), it is investigated, if antenna efficiency can be increased by the introduction of a LDS ground plane. Differences in antenna performance are presented on the example of simple LDS and wire monopole-antennas for 5:9GHz (IEEE 801.11p, ITS G5). Gain, efficiency, return loss and the radiation patterns of an LDS design, a CFC and an aluminum ground plane are compared.

Measurement and modelling of interference alignment impairments

Interference alignment is a linear precoding technique that eliminates interference in the K-user interference channel. We present measurement results and identify the performance limiting factors that occur under real conditions. In our setup, we found the main causes of impairment to be outdated channel state information in varying channels, thermal noise at the receiver and transmit impairments. We propose a simplistic channel model that is capable of capturing these effects and allows to investigate their impact on the achievable rate.

Pattern reconfigurable antenna with four directions hidden in the vehicle roof

Chassis integrated antenna cavities offer ten times the space of conventional automotive roof mounted antenna modules and can be fully concealed beneath the roofline. A pattern reconfigurable antenna for 2.6 GHz LTE is measured inside an automotive chassis cavity. The antenna can be electrically reconfigured to radiate towards the front, back, left or right side of the vehicle. Measurement results show that the antenna retains this ability when being hidden beneath the roof, proving that it is possible and feasible to hide antennas utilizing pattern diversity inside chassis cavities.

Carbon Fiber Reinforced Polymer with Shredded Fibers: Quasi-Isotropic Material Properties and Antenna Performance

A carbon fiber reinforced polymer (CFRP) laminate, with the top layer consisting of shredded fibers, is proposed and manufactured. The shredded fibers are aligned randomly on the surface to achieve a more isotropic conductivity, as is desired in antenna applications. Moreover, fiber shreds can be recycled from carbon fiber composites. Conductivity, permittivity, and permeability are obtained with the Nicolson-Ross-Weir method from material samples measured inside rectangular waveguides in the frequency range of 4 to 6 GHz. The decrease in material anisotropy results in negligible influence on antennas. This is shown by measuring the proposed CFRP as ground plane material for both a narrowband wire monopole antenna for 5.9 GHz and an ultrawideband conical monopole antenna for 1–10 GHz. For comparison, all measurements are repeated with a twill-weave CFRP.

CARBON FIBER REINFORCED POLYMER WITH ISOTROPIC 60 GHZ REFLECTIVITY

Carbon fiber reinforced polymer (CFRP) is measured as reflector material for millimeter waves at 60 GHz. Reflectivity is measured to characterize material anisotropy in a mono-static setup. Disc shaped material samples are rotated in steps of one degree. Four commonly employed CFRP are investigated: unidirectional fibers, plain-weave, twill-weave and fiber shreds. Results show that the unidirectional CFRP and twill-weave CFRP are anisotropic, while the remaining materials are isotropic within measurement accuracy.

Angle-dependent reflectivity of twill-weave carbon fibre reinforced polymer for millimetre waves

Twill-weave carbon fibre reinforced polymer is measured as reflector material for electromagnetic waves at 60 GHz. The reflectivity at millimetre wavelength shows a predominant direction, which coincides with the diagonal pattern of the twills top layer. In the remaining directions the investigated 2/2 twill-weave composites reflectivity is almost isotropic.

Measurement and analysis of LTE coverage for vehicular use cases in live networks

We conducted drive test measurements in a live LTE 1800 MHz network to evaluate mobile network performance of User Equipments (UEs) located inside and outside a pickup truck. The measurement campaign is performed in Kosovo, starting from Prishtina to the south-western Albanian border. Knowledge of base station locations and cell load during the measurements is made available from the service provider. This is crucial to determine whether the bit rate is limited by network availability, cell load, or propagation effects. To provide reliable in-vehicle coverage, it is necessary to determine the penetration loss. In this paper, we present the first results and show that the penetration loss varies by up to 10.58 dB.