Robert Geise

Measurements and Analysis of an In-Car UWB Channel

Car manufacturers have been showing great interest in setting up ultra-wideband (UWB) systems due to the offered high data rates. In this paper, the fundamental features of the in-car UWB channel in terms of large-scale and small-scale parameters are investigated. These values are based on measurement data collected with a vector network analyzer (VNA) in the frequency band of 3-8 GHz. With the aid of the measurements, simple preliminary empirical models have been derived describing both, path loss as well as small-scale features of the channel. The results are shown for LOS and NLOS situations as well as for an empty car and a car occupied with persons.

On the Influence of Scattering From Traffic Signs in Vehicle-to-X Communications

As an important scatterer in vehicle-to-X (V2X) communication scenarios, traffic signs frequently appear along roads and can affect the propagation channel appreciably. Although traffic signs can be considered as an important part in such scattering scenarios, knowledge of their bistatic radar cross section (RCS) is still absent. This paper presents an integration of the analytical models, full-wave simulation, measurement, and validation of the bistatic RCS of three types of representative traffic signs for V2X communication. First, the total RCS of the traffic signs is calculated by summing up the field contributions of the individual parts with their own phase relationships. Furthermore, simulations using full-wave analysis are performed to validate the analytical models for RCSs in the far field under plane-wave illumination. Since the high-frequency calculation techniques used here are applicable only under plane-wave excitation, the traffic-sign parts are divided into small elements, where this precondition is locally valid. Measurements are conducted in an open-area test site at the National Metrology Institute of Germany to validate the model in the near field (spherical wave from a point source). Corresponding comparisons show that the method of decomposing the traffic sign into small parts supports an effective way to embed the analytical models into ray-tracing tools, thus improving propagation modeling in V2X communication.

UWB propagation channels within an aircraft and an office building environment

Path loss at higher distances is much higher for NLOS in the office due to solid walls in the propagation path. In LOS, the results are converging with increasing distance. In our indoor campaign, these large distances can only be found on corridors. At small distances the path loss is about 10 dB less in the aircraft than in the office for all frequencies, which can also be observed in PL0. The delay spread is higher in the aircraft but converges with the LOS configuration in the office. However, the maximum excess delay is smaller for indoor LOS. This leads to the conclusion that the UWB channel in the aircraft fuselage is comparable to an indoor corridor with one important difference: there are much more relevant multi path contributions in the received signal than in office environment mainly caused by metal structures in the aircraft cabin. Strong reflecting environments lead to a limitation of data rate in single carrier systems. It can be exploited best by OFDM- and MIMO technologies with an appropriate system design. So UWB technology would be very suitable for this environment.

Alignment and illumination issues in scaled THz RCS measurements

Radar cross section (RCS) measurements are widely employed for the target identification of objects such as aircraft. The RCS of large, complex geometries is usually determined in a well defined, scaled experimental setup. In such a setup, the measuring frequency equates the frequency of interest multiplied by the scaling factor of the model. For high scaling factors, frequencies well above 100 GHz result so that conventional microwave equipment reaches its technological limits. In this paper, we discuss the use of a fiber coupled terahertz time domain spectroscopy system for angle dependent RCS measurements. Several measurements on simple objects like metal plates with corresponding simulations are performed. We also investigate how angular misalignment and displacement of the scatterer effects the measurement results. Moreover, we discuss the influence of non planar incident wavefronts and compare experimentally obtained data to simulations using an enhanced physical optics model.

Scaled Measurements of Instrument-Landing-System Disturbances Due to Large Taxiing Aircraft

It is commonly known that the directional pattern of the instrument landing system (ILS)-localizer antenna system, which constitutes the landing-course information for approaching aircraft, can be disturbed by reflections from large aircraft on the ground. Therefore, airport operators are interested in knowing configurations of landed and taxiing aircraft that lead to such ILS disturbance scenarios. Measurements on a real airport for investigating such scenarios are very cost-intensive and not sufficiently possible due to availability reasons. Therefore, a new scaled measurement setup is presented. Scaling down an aircraft by the factor of 144 requires a scaled ILS-localizer operating at a frequency of nearly 16 GHz, the development and realization of which is presented in this paper. Using this scaled ILS-localizer, measurements with an Airbus A380 and a Boeing B747 are conducted showing the feasibility of the scaled approach. Several configurations are shown where those aircraft lead to interferences of the ILS, exceeding allowed tolerances. A comparison of the reflection behavior of both aircraft shows only slight differences. Additionally, this paper presents the derivation of the bistatic radar cross section of both aircraft to be applicable to scenarios with arbitrary ILS patterns.

Electrically small ultra wideband antenna for EMC measurements in vehicles optimized by electromagnetic simulation

A monoconical antenna type has been selected and successfully optimized by a electromagnetic field simulation program. A real antenna was constructed with the parameters found by several simulated parameter sweeps. The comparison between simulation and real antenna shows a good agreement and the comparison between an antenna constructed with the optimal half opening angle derived from theory and the new design parameters revealed that an enormous reduction of size of the antenna is realizable while still having an acceptable matching antenna with a rather smooth frequencies response. For applications where size is one of the most important parameters, this design is to be preferred. A pre-version of these antennas has been successfully used for example in [6]. In future work the influence on receiving characteristic of the polarization of the incident wave should be investigated.

Indoor channel measurements of point-to-point ultra broadband short range links between 75 GHz and 110 GHz

Recently, frequencies at 60 GHz and beyond have been regaining interest for high-speed wireless communication applications (Laskar, et al., August 2007), (Piesiewicz, et al.). Decreasing technology costs on one hand and an increasing demand for higher data rates on the other hand, make a spectral shift to the millimeter wave range desirable. In the long run, the sub-millimeter wave range could be of interest, considering large available bandwidths. Emerging applications encompass uncompressed high definition video streaming and ultra fast data transfers. Especially the latter group will be primarily operated in point-to-point line of sight (LOS) short range links of several to few tens centimeters, where examples include file sharing and generic data transfers between computers and peripheral devices as well as kiosk downloading to or from a handheld, as envisaged by the IEEE 802.15.3c standardization body.

Feasibility study on scaled bistatic RCS measurements of aircraft in W-band to investigate misguidance by the Instrument-Landing-System

In this paper a measurement technique is presented, which allows the derivation of scaled bistatic radar cross sections of objects at ILS frequencies with a very simple measurement setup and an easy post processing procedure. Its functionality is proven with simple reference objects, which can be calculated by common simulation tools. First sets of bistatic RCS are presented for the large aircraft A380 and B747. With a wider span of the observation angle and a more sophisticated measurement setup, enhancing RCS measurements within only one plane to a three dimensional observation area, it becomes feasible to measure the bistatic RCS profile, that is necessary to investigate ILS disturbances for a complete landing approach at decreasing height of aircraft. Additionally, the use of focusing lenses can improve the measurement dynamics and accuracy and is of interest for further investigations.

Navigation Signal Disturbances by Multipath Propagation – Scaled Measurements with a Universal Channel Sounder Architecture

Abstract The performance of navigation systems is always reduced by unwanted multipath propagation. This is especially of practical importance for airborne navigation systems like the instrument landing system (ILS) or the VHF omni directional radio range (VOR). Nevertheless, the quantitative analysis of corresponding, potentially harmful multipath propagation disturbances is very difficult due to the large parameter space. Experimentally difficulties arise due to very expensive, real scale measurement campaigns and numerical simulation techniques still have shortcomings which are briefly discussed. In this contribution a new universal approach is introduced on how to measure very flexibly multipath propagation effects for arbitrary navigation systems using a channel sounder architecture in a scaled measurement environment. Two relevant scenarios of multipath propagation and the impact on navigation signals are presented. The first describes disturbances of the ILS due to large taxiing aircraft. The other example shows the influence of rotating wind turbines on the VOR.

UWB aircraft transfer function measurements in the frequency range from 2 to 8 GHz

In this paper the determination of transfer functions from inside an Airbus A319 to outside the aircraft in a frequency range from 2 GHz to 8 GHz is presented. Two different aspects have been investigated. The first is the determination of the fuselage attenuation of the aircraft in order to see, if existing airport communications and radar systems could be disturbed by onboard installed equipment. The second concerns possible coupling from inside the aircraft to different relevant aircraft navigation and communication antennas which are mounted outside the aircraft along the fuselage. The different results of these two measurements are presented and possible interferences with existing systems are discussed.