Björn Neubauer

Microstrip antennas for remote moisture sensing using passive RFID

The paper presents how materials with a high ability of absorbing moisture can be used with microstrip antennas and passive RFID chips for constructing remotely read moisture sensors. The concept is based on pairs of microstrip antennas, applied on the same piece of PCB and each equipped with one RFID chip, where one antenna is covered by the moisture absorbent material and the other is left open. In a humid or wet environment the moisture concentration is higher in the absorbent material than in the surrounding environment which causes degradation to the embedded antenna both in terms of dielectric losses and change of input impedance. The level of relative humidity or the amount of water in the absorbent material is determined for a passive RFID system by comparing the difference in RFID reader output power required to power up respectively the open and embedded tag. While it has previously been shown how this can be accomplished with simple one-layer antennas we here look into using microstrip antennas to get around the problem with high influence from background material. Typical applications include moisture detection in buildings, especially from leaking water pipe connections hidden beyond walls or simply to measure the level of relative humidity at hidden locations.

EMC analysis including receiver characteristics - pantograph arcing and the instrument landing system

This contribution presents a sophisticated compliance study, whether emissions of transient sparks occurring between pantographs of rails and overhead lines can interfere with receivers of the instrument-landing-systems (ILS) onboard aircraft. Though the investigated interference scenario actually is quite specific and arose in the context of the enhancement of the airport Frankfurt in Germany it comprises several fields of electromagnetic compatibility where yet insufficient approaches exist. In particular, absolute field strength measurements of transient signals in a non-ideal measurement railway environment are conducted. Another new aspect in this study is, that the individual receiver characteristics are taken into account, e.g. non-linearity and band pass behavior, where usually only simple continuous wave signals in an interference path loss model are considered. Consequently, a setup is presented, where an individual measured interference signal from a real environment is synthesized and fed into a real EMC sink. This procedure however, could be generalized to any other receiver or interference source.

A new thermally activated battery cell-based forest fire detection and monitoring system

Detection of forest wildfires at early stages can significantly improve the success of fire fighting and thus it contributes to the damage and cost reduction. Surface deployed sensor networks linke ...

Vectorial channel sounding in a reverberation chamber - measuring dynamic behaviour

The key aspect of reverberation chambers (RC) is the statistic behavior of the field inside including the influence of the moving, respectively rotating mode stirrer. By means of a vectorial channel sounder presented in this contribution the dynamic influences of the stirrer are investigated with respect to its mechanical relaxation time and its efficiency. Additionally, the ability of vectorial channel sounding allows to simultaneously measure the influence of different antenna orientations and polarizations on time-variant propagation channels investigating spatial-dependent effects in the RC. Measurements are done on a small time scale that is not accessible by standard field probe sampling times. Results also indicate dynamic effects of the RC even for a static case, where the RC may be mechanically excited by external sources, respectively vibrations.