A new shielding effectiveness measurement method based on a skin-effect transmission line coupler

We propose a new convenient material shielding effectiveness measurement method based on a skin-effect transmission line coupler. The method is somewhat similar to the arrangement with two coupled TEM cells known from literature. The transmission line coupler consists of a pair of identical transmission line 2-port devices. Each device contains a coaxial waveguide, with a circular inner conductor and an outer conductor having a square cross section. One side of the outer conductor is left completely open as a slot. The slot is surrounded by a large metal housing to contact the two halves. As a measure for the shielding effectiveness the coupling between the two devices is measured in terms of scattering parameters after the test material is brought between the two halves. The devices can be used in a range from low frequencies to a few GHz

Airborne field strength monitoring

In civil and military aviation, ground based navigation aids (NAVAIDS) are still crucial for flight guidance even though the acceptance of satellite based systems (GNSS) increases. Part of the calibration process for NAVAIDS (ILS, DME, VOR) is to perform a flight inspection according to specified methods as stated in a document (DOC8071, 2000) by the International Civil Aviation Organization (ICAO). One major task is to determine the coverage, or, in other words, the true signal-in-space field strength of a ground transmitter. This has always been a challenge to flight inspection up to now, since, especially in the L-band (DME, 1GHz), the antenna installed performance was known with an uncertainty of 10 dB or even more. In order to meet ICAO's required accuracy of ±3 dB it is necessary to have a precise 3-D antenna factor of the receiving antenna operating on the airborne platform including all losses and impedance mismatching. Introducing precise, effective antenna factors to flight inspection to achieve the required accuracy is new and not published in relevant papers yet. The authors try to establish a new balanced procedure between simulation and validation by airborne and ground measurements. This involves the interpretation of measured scattering parameters gained both on the ground and airborne in comparison with numerical results obtained by the multilevel fast multipole algorithm (MLFMA) accelerated method of moments (MoM) using a complex geometric model of the aircraft. First results will be presented in this paper

Measurement comparison among Time-Domain, FTIR and VNA-based spectrometers in the THz frequency range

In this paper we present the outcome of the first international comparison in the terahertz frequency range among three different kinds of spectrometers. A Fourier-Transform infrared spectrometer, a vector network analyzer and a time-domain spectrometer have been employed for measuring the complex refractive index of three travelling standards made of selected dielectric materials in order to offer a wide enough range of parameters to be measured. The three spectrometers have been compared in terms of measurement capability and uncertainty

Safety Checkpoints

partially_open9sìopenKazemipour, Alireza; Kleine-Ostmann, Thomas; Schrader, Thorsten; Allal, Djamel; Charles, Michael; Zilberti, Luca; Borsero, Michele; Bottauscio, Oriano; Chiampi, MarioKazemipour, Alireza; Kleine Ostmann, Thomas; Schrader, Thorsten; Allal, Djamel; Charles, Michael; Zilberti, Luca; Borsero, Michele; Bottauscio, Oriano; Chiampi, Mari

Exposure Setup and Dosimetry for a Study on Effects of Mobile Communication Signals on Human Hematopoietic Stem Cells in vitro

In this paper we describe the design of an exposure setup used to study possible non-thermal effects due to the exposure of human hematopoietic stem cells to GSM, UMTS and LTE mobile communication signals. The experiments are performed under fully blinded conditions in a TEM waveguide located inside an incubator to achieve defined environmental conditions as required for the living cells. Chamber slides containing the cells in culture medium are placed on the septum of the waveguide. The environmental and exposure parameters such as signal power, temperatures, relative humidity and CO2 content of the surrounding atmosphere are monitored permanently during the exposure experiment. The power of the exposure signals required to achieve specific absorption rates of 0.5, 1, 2 and 4 W kg−1 are determined by numerical calculation of the field distribution inside the cell culture medium at 900 MHz (GSM), 1950 MHz (UMTS) and 2535 MHz (LTE). The dosimetry is verified both with scattering parameter measurements on the waveguide with and without containers filled with cell culture medium and with temperature measurements with non-metallic probes in separate heating experiments

Terahertz time-domain spectroscopy and imaging of artificial RNA

This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsexpress.org/abstract.cfm?id=84667. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.We use terahertz time-domain spectroscopy (THz-TDS) to measure the far-infrared dielectric function of two artificial RNA single strands, composed of polyadenylic acid (poly-A) and polycytidylic acid (poly-C). We find a significant difference in the absorption between the two types of RNA strands, and we show that we can use this difference to record images of spot arrays of the RNA strands. Under controlled conditions it is possible to use the THz image to distinguish between the two RNA strands. We discuss the requirements to sample preparation imposed by the lack of sharp spectral features in the absorption spectra.Bernd Fischer, Matthias Hoffmann, Hanspeter Helm, Rafal Wilk, Frank Rutz, Thomas Kleine-Ostmann, Martin Koch, Peter Jepse

Metamaterial Polarization Converter Analysis: Limits of Performance

In this paper we analyze the theoretical limits of a metamaterial converter that allows for linear-to- elliptical polarization transformation with any desired ellipticity and ellipse orientation. We employ the transmission line approach providing a needed level of the design generalization. Our analysis reveals that the maximal conversion efficiency for transmission through a single metamaterial layer is 50%, while the realistic re ection configuration can give the conversion efficiency up to 90%. We show that a double layer transmission converter and a single layer with a ground plane can have 100% polarization conversion efficiency. We tested our conclusions numerically reaching the designated limits of efficiency using a simple metamaterial design. Our general analysis provides useful guidelines for the metamaterial polarization converter design for virtually any frequency range of the electromagnetic waves.Comment: 10 pages, 11 figures, 2 table

Highly-Sensitive Thin Film THz Detector Based on Edge Metal-Semiconductor-Metal Junction

Terahertz (THz) detectors have been extensively studied for various applications such as security, wireless communication, and medical imaging. In case of metal-insulator-metal (MIM) tunnel junction THz detector, a small junction area is desirable because the detector response time can be shortened by reducing it. An edge metal-semiconductor-metal (EMSM) junction has been developed with a small junction area controlled precisely by the thicknesses of metal and semiconductor films. The voltage response of the EMSM THz detector shows the clear dependence on the polarization angle of incident THz wave and the responsivity is found to be very high (similar to 2,169 V/W) at 0.4 THz without any antenna and signal amplifier. The EMSM junction structure can be a new and efficient way of fabricating the nonlinear device THz detector with high cut-off frequency relying on extremely small junction area

Numerical dosimetric calculations for in vitro field expositions in the THz frequency range

Field exposition experiments have been initiated by the German Federal Office for Radiation Protection (Bundesamt für Strahlenschutz – BfS) to examine genotoxic effects of THz radiation in vitro. Two different human skin cell types are exposed to continuous-wave radiation at six distinct frequencies between 100 GHz and 2.52 THz originating from different sources of THz radiation under defined environmental conditions. The cell containers are irradiated with free space power flux densities between 0.1 mW/cm2 and 2 mW/cm2 measured traceable to the SI units. For meaningful results, dosimetric calculations using the finite differences time-domain method have been performed in order to access the fields and consequently the specific absorption rate (SAR) in the cell layer

Concept and design of a UAS-based platform for measurements of RF signal-in-space

Field strength or signal-in-space (SIS) measurements have been performed by using manned helicopters, aircrafts or from ground level using extendable masts. With the availability of unmanned aerial systems (UAS) such as multicopters a new versatile platform for SIS measurements is deployable. Larger types show up to eight individually driven electric motors and controllers (therefore called octocopter). They provide the ability to fly along predefined traces, to hover at waypoints and to initiate other actions when those have been reached. They provide self-levelling and stabilisation and moreover, they may gear at a point of interest regardless of their actual position, e.g. during their flight around a tower. Their payload mainly depends on the platform size and allows integration of complex measurement equipment. Upgrading their navigation capabilities including state-of-the-art global navigation satellite system (GNSS) and ground station transmitter (real-time kinematic – RTK) enables precise localisation of the UAS. For operation in electromagnetic harsh environments a shielding can be considered and integrated into the concept. This paper describes concept and design of an octocopter and its instrumentation, along with applications in recent projects, in which we measure and validate terrestrial navigation systems applied in air traffic and the weather forecast services. Among those are instrumentation landing systems (ILS), VHF omnidirectional radio ranges (VOR), airport traffic and weather radars as well as military surveillance radars, and UHF wind profilers. Especially to investigate the possible interaction of VORs and radars with single wind turbines (WT) or wind power plants has become a major request of economy, military and politics. Here, UAS can be deployed to deliver measurement data investigating this interaction. Once developed and setup to a certain extent, UAS are easy and cost-efficient to operate. Nonetheless, due to their compact size, UAS will have rather low interaction with the electromagnetic field to be measured compared to the operation of manned helicopters