Henning Früchting

GPS patch antenna with photovoltaic solar cells for vehicular applications

This paper describes the application of photovoltaic (PV) solar cells in planar antenna structures. The radiating patch element of a planar antenna is replaced by a solar cell. The original feature of a solar cell (DC current generation) remains, but additionally the cell is now able to receive and transmit electromagnetic waves. Both single solar cells as well as solar cell arrays can be used as antennas. However, the DC connection of the solar cells must be considered. By means of an elaborated series connection of the solar cells a harmful influence on the antenna properties may be avoided. Besides a general technical description, a solar-cell antenna for GPS applications is presented in detail. As a demonstrator, an aperture coupled patch antenna has been realised, which is suited for integration in vehicular glass roofs. The solar cell antenna is manufactured with commonly used production methods for solar modules. It turned out that some of the used materials degrade the antenna properties. Nevertheless, the comparison of measured and simulated antenna properties shows a good agreement, and the antenna works well with commercial GPS receivers. The DC voltage of the solar cells is about 18 V. Thus support of the car battery and the power supply is possible, which enables new applications like permanent cabin ventilation.

Investigation of planar antennas with photovoltaic solar cells for mobile communications

This paper describes the application of photovoltaic (PV) solar cells in planar antenna structures. The radiating patch element of a planar antenna is replaced by a solar cell. Furthermore radiating slots are built due to the cell spacing in a solar cell array. The original feature of a solar cell (DC current generation) remains, but additionally the solar cell is now able to receive and transmit electromagnetic waves. Both single solar cells as well as solar cell arrays can be used as antennas. At first some basics regarding the RF properties of solar cell patches are discussed. The efficiency of solar cell antennas is measured by means of the Wheeler Cap method, which is investigated by means of numerical simulations. The lossy substrate of the feed lines has the strongest influence on the antenna efficiency. Finally two applications are presented: a solar cell GPS antenna for vehicular applications and a solar cell slot antenna for mobile communications (GSM). The aim is to integrate these antennas into vehicular glass roofs which are covered with photovoltaic solar cells in order to deliver the electric power for the indoor ventilation of the car. The GPS antenna provides circular polarisation and a main lobe in zenith direction whereas the GSM antenna is vertically polarized and has a monopole-like radiation pattern. Both antennas are built up with commonly used solar cells. The comparison of measured and simulated antenna properties shows a good agreement.

Wideband measurements of channel characteristics in deterministic indoor environment at 1.8 GHz and 5.2 GHz

Results are pre:. ed and discussed for TimeVariant Impulse Responses, Scattering Functions and TimeFrequency Correlation Functions, which have been determined from measured data in indoor environment at 1.8 GHz and 5.2 GHz. The environment has been chosen to be as much deterministic as possible, to get a basic insight into the influence of propagation on these functions. Evaluation methods used in this paper are shown to be valuable means for the examination of channel characteristics, which is essential for the choice of appropriate channel models. With respect to measurements at different frequencies, distinct similarities appeared, especially for the Scattering Functions and the Time-Frequency Correlation Functions.

Ray optical approach for a wideband indoor wave propagation model with moving receiver

For investigations on channel characteristics in a deterministic indoor environment, a ray-tracing-based wideband wave propagation model with moving receiver is proposed. Considering multiple reflections and transmissions to be basic propagation effects inside buildings, the space-variant complex channel impulse response and the scattering function are calculated and compared to wideband measurements at 1800 MHz carried out in a shelter. Good agreement was found for delay times, detection of propagation paths and general characteristics of the impulse responses both for the LOS and NLOS cases. Yet, especially the magnitudes in the NLOS case suffer, for example, from uncertainties caused by an arbitrary choice of material parameters. Further investigations have to show, whether it is possible to apply the model to less deterministic environments.

Calculation of System and Correlation Functions for WSSUS Channels from Wideband Measurements

System and correlation functions of WSSUS channels are commonly accepted means for channel description in mobile communications. After a brief recapitulation of the theory for WSSUS channels, methods are derived for using system and correlation functions for the examination of measured channel characteristics. The derived methods additionally lead to a simple interpretation of the relations between the functions. Finally results are given for the Time-Variant Impulse Response, the Scattering Function and the Time-Frequency Correlation Function calculated from measured data in an indoor environment

Comparative Numerical Study of Antennas for Hand Held Mobile Telephones

The Finite Integration Algorithm (FIA) is used for the analysis of monopole and Radiation-Coupled Dual-L (RCDLA) antennas for personal communications at the GSM frequency of 900 MHz. It is found that 44% of the power delivered to the monopole is absorbed by the user, compared to only 20% for the RCDLA. The maximal local Specific Absorbtion Rate SAR inside the head for a transmitted power of 1 W for the monopole and RCDLA is 2 mW/cm 3 and 0.9 mW/cm 3 respectively. It is also found that the RCDLA has a bandwidth of only 30 MHz, and that the users hand has a strong influence on its resonant frequency. The monopole, on the other hand has a large bandwidth, and its impedance is not so sensitive to the presence of the user.

Channel Characterization & Modelling

The transition from second generation mobile systems to third generation naturally involved the necessity towards smaller cell radii. Therefore the demand and standards on measurement systems and wave propagation models have changed in dependance on the properties of the propagation environment models. Two different fundamental methods of modeling can be distinguished. Those based on statistical methods and are dependent on channel measurements and those based on deterministic methods and are dependent on ray-tracking techniques.

Determination of reflection and transmission properties of wall-like objects by evaluating the scattering function

In the present paper an alternative method of analysis is proposed to extract reflection and transmission properties of arbitrary wall-like objects from wideband measurements of radio channels in the GHz-range. Mean effective reflection and transmission factors are derived depending on the frequency of the electromagnetic waves, polarization and incidence angle on the surface of the object. Working with ratios of quantities most systematic errors are compensated for automatically which can be seen as an advantage of this method. By classifying different wall-types the derived reflection and transmission coefficients can be used in look-up tables to improve the prediction quality of ray-tracing models, especially for very inhomogeneous environments e.g. indoor areas.

Integrierte Planarantenne für Handfunktelefone und ihre Optimierung

Übersicht Es wird eine neue Antenne für Mobilfunkanwendungen im 1,8-GHz-Band (DCS 1800) vorgestellt, die sehr klein und in das Handygehäuse integrierbar ist. Diese Antenne wird als Dual Meandering Antenna (DMA) bezeichnet. Sie ist auf der Rückseite des Telefongehäuses angebracht. Die DMA stellt eine Weiterentwicklung der RCDLA (Radiation Coupled Dual-L Antenna) [1] dar. Die DMA ist eine platzsparende integrierbare Antenne, die durch einen zweifachen Knick des aktiven und passiven Strahlerelements entsteht. Die Eigenschaften der Antenne werden in dieser Arbeit diskutiert. Die Auswirkungen der Strahlergeometrie auf Impedanz und Bandbreite der Antenne werden ausführlich erläutert und daraus Hinweise zur Optimierung abgeleitet. Eine bezüglich der Bandbreite optimierte Antenne wird entwickelt und der Einfluß des Benutzers untersucht. Ebenso wird die Strahlungscharakteristik der Antenne mit und ohne Benutzer dargestellt, wobei die Abstrahlung in Richtung des Kopfes gegenüber einer Monopolantenne reduziert ist. Die numerische Analyse der Antenne erfolgt mit dem Programmpaket MAFIA.

Numerische Analyse aperturgekoppelter Streifenleitungsantennen mit MAFIA

Microstrip and planar antennas are widely used in the field of mobile communication and radar applications. For an accurate calculation of the antenna properties efficient numerical techniques are used. These are very valuable design tools. An aperture coupled microstrip antenna for applications in the X-Band (9.6 GHz) is simulated by means of MAFIA using the FIT-Algorithm (Finite Integration Technique). The results are compared with a simulation based on a combination of the integral equation method and the method of moments. The simulation results show very good agreement both with measurements of the reflection coefficient and the farfield of the antenna, and with results from the combined method of integral equation and method of moments.