Mustafa Cetintas

Measurement of electromagnetic radiation from GSM base stations

Electromagnetic radiations from GSM (global service for mobile communication) base stations were measured in the far-field region by using directional antennas (biconical-log/hybrid, horn antenna) and isotropic electric field probes and detected signals were analyzed by using low-resolution bandwidth (30 Hz) spectrum analyzer and field probe meter respectively. Electric fields of the electromagnetic radiations were measured in x, y and z orthogonal directions with vertical and horizontal polarizations. Amplitude fluctuation of electromagnetic radiation of GSM base station were detected at long time interval (more than 8 hours) and analyzed using standard deviation and Allan variance statistics. The results and uncertainties of the electric field measurements by biconical-log/hybrid antenna, horn antenna and electric field probe were compared. The measured electric field values of GSM base stations were compared to the value of reference levels for general public exposure to time-varying electric fields limits of ICNRP guidelines.

Characterization of a Far-Field Microwave Magnetic Field Strength Sensor Based on Double Radiooptical Resonance

We experimentally investigated the resonance interaction of laser and microwave fields with 133Cs atomic gas in far-field and free-space conditions. The observed double radiooptical resonance (DROR) on the D2 line of Cs atoms was used as a novel-type field sensor, based on the laser spectroscopy technique, for the detection and investigation of the time-varying magnetic field. The effects of the Cs cell length, both laser and microwave powers, and their polarizations to the changing amplitude of the DROR signal were investigated. Almost linear dependencies of the DROR signal amplitude with both laser and microwave powers have been observed. The splitting of DROR signal under a constant magnetic field was detected. The time response of the sensor system was investigated under pulsed microwave. The amplitude fluctuation of the microwave magnetic field was measured using the DROR signal and the isotropic probe simultaneously. The stability of amplitude fluctuations of the microwave field with time was analyzed by using Allan variance statistics.

Sensing of RF Magnetic Fields Using Zeeman Splitting of Double Radiooptical Resonance and a New Approach to Helmholtz Coil Calibrations

We experimentally investigated the resonance interaction of laser, microwave, and radio frequency (RF) fields with Cesium (133Cs) atomic gas. The observed Zeeman components produced by means of an external static magnetic field on the double radiooptical resonance (DROR) were used as a frequency-adjustable RF field detection sensor based on the laser spectroscopy technique. The change in the RF interaction frequency of Zeeman components with the increasing level of the static magnetic field was investigated and linear dependence of the RF interaction frequency of the Zeeman components on the external static magnetic field was observed. In addition, the change in the amplitude of the Zeeman components with the level of RF fields was investigated and an approximately linear relation in certain regions was detected. We also studied the relation of the Zeeman component amplitudes with laser and microwave powers. Finally, a new approach to Helmholtz coil calibrations by using this atomic sensor is discussed.

Optical feedback in diode laser for sound-pressure measurement

We describe a method for a sound pressure measurement in a small volume based on optical feedback in single-mode diode laser. The shift in the operating frequency of diode laser due to the vibration of a testing object under explosion to the sound field are used for a determination of a sound pressure amplitude. The working range and possible applications of the proposed method are discussed.

Application of the differential Fabry–Perot interferometer in angle metrology

A differential Fabry–Perot interferometer (DFPI) was applied for the detection of ultra-small angles in the level of nanoradian (nrad) precision. During application, down to 1 nrad angular steps were generated using the available high precision small angle generator (HPSAG) and these steps were detected using the frequency stabilised lasers as an alternative and outperforming method to conventional angle interferometers. The use of the DFPI provided the displacement measurements (further angular displacements through optical configuration) with picometre sensitivity free from linearity errors. A coefficient of 1.436 964 × 10−9 arcsec Hz−1 (about 7 × 10−6 nrad Hz−1) for the DFPI was calculated using the generated–measured traceable angular values of the HPSAG and various angular steps were measured by the DFPI using this coefficient. The tests were carried out up to the range of 0.5 arcsec (2500 nrad) in angular steps down to 1 nrad. The work is in progress under the SIB58 Angles project and aims to reduce the noise level of the HPSAG with further statistical process and later to extend the measurement range of the DFPI readings with the same optical configuration, rather than using different beam spacing configuration in the DFPI.

Effects of sensor positions on military radiated susceptibility tests

The MIL-STD 461F RS103 test is one of the essential radiated immunity tests for military equipment. Unlike the pre-calibration method of commercial radiated immunity tests such as EN61000-4-3, the RS103 test requires the placement of an electrical field sensor close to the application point of the EUT (Equipment Under Test) and also requires active-leveling of the field based on the feedback from the sensor without use of a pre-calibrated field. In most cases, the position of the sensor is not certain in the standard and every laboratory uses their own selections for probe positions which are close to the application region. In this research, we showed that the chosen sensor position directly affects the value of power injected into the antenna, consequently affects the test results significantly for a constant electrical field value owing to the reflections coming from the EUT itself.

Influence of dielectric support on military radiated emission tests above 30 MHz

We experimentally investigated the influence of dielectric supports used on RE102 radiated emission tests of the MIL-STD-461F EMC standard for table-top and conductive surface mounted Equipment Under Test (EUT). A variety of dielectric materials which are commonly selected as supports under EUT cables in RE102 tests were investigated by using an actual RE102 test setup in a semi anechoic chamber. Each investigated material yielded different effects on RE102 test results in comparison to the case without support, in other words, with the air support.

Alternative conducted immunity tests

Conducted immunity tests are always performed by the use of CDNs in laboratories in accordance with the standard EN61000-4-6. However, it is not always possible to use CDNs because of some limitations. If the EUT (Equipment Under Test) has large dimensions or high currents, it is not, most of the time, possible to send it to an EMC laboratory or to use CDNs during the test. As a consequence, usage of BCI probes is inevitable in industry. In this paper, we compared the laboratory setup installed with CDNs and alternative setups installed directly on mains without any CDNs in terms of loop impedances and injected loop currents. We also established a link based on the loop impedances and the injected currents on the test loops between the two setups. Finally, a first serious step was taken to establish the fundamentals of alternative conducted immunity tests based on the impedance measurements of test loops for industry.

Alternative conducted immunity testing with multiple CDNs and wire winding

Conducted immunity tests are always performed by use of Coupling Decoupling Networks (CDN) in laboratories in accordance with the standard EN61000-4-6. However, it is not always possible to use CDNs because of some limitations. If the Equipment Under Test (EUT) has large dimensions or high currents, it is not possible to use CDNs during tests. As a consequence, alternative methods are required in industry. In this paper, we firstly investigated the multi-CDN method which facilitates use of CDNs also for high-current EUTs by splitting mains current into several pieces that one CDN can handle. We also investigated simple wire-windings instead of cumbersome injection clamps to be applied to thick cables or cables in narrow places as an alternative to standard laboratory methods.

Investigation of different alternative radiated immunity test methods

Radiated immunity measurements are commonly performed by using field uniformity at 3 m in laboratories in anechoic chambers in accordance with the standard IEC61000-4-3. However, the test of Equipment Under Test (EUT) sometimes cannot be carried out in laboratories due to several restrictions. In case of EUT with large dimensions, high power consumptions and/or auxiliary devices which are attached to the EUT, it is not possible to use laboratory facilities during tests. As a consequence, on-site radiated immunity tests are required in industry. On the other hand, radiated immunity tests and establishment of a field uniformity with 16-points have many challenges in industry and almost impossible in industrial environments due to uncontrolled reflections and narrow testing environment, for that reason alternative EMC test methods at standard or non-standard distances become unavoidable in industry. In this research, we have experimentally investigated different radiated immunity test methods commonly used in industry at standard or non-standard distances and compared them with the reference field uniformity method applied at 3 m, finally proposed the most acceptable solution for industrial environments.