Soydan Cakir

Improving time-domain EMI measurements through digital signal processing

This article is intended to provide a set of recommended practices for improving of the Time-Domain EMI measurement systems by means of digital signal processing. We have focused on two major aspects: the optimal configuration settings of the direct measurement equipment and the deployment of algorithms to process the measurement result. In that sense, we believe that general purpose time-domain instruments, as oscilloscopes, can be successfully used as an alternative hardware to measure EMI, since they provide accurate and reliable results, surpassing the conventional frequency-domain approach when transient disturbances are present.

Antenna Calibration for EMC Tests and Measurements

An antenna is calibrated in an open-field test site (OFTS) and/or an anechoic chamber, which facilities themselves need calibration. The procedures for calibrated test sites (CALTS) are given in the CISPR and ANSI/IEEE standards. The characteristic parameter for calibrated test sites is the normalized site attenuation (NSA). Theoretical calculations and practical measurements of normalized site attenuation are first presented. Antenna-factor (AF) and/or absolute-gain measurement methods are then reviewed. Finally, an alternative antenna calibration approach is given in this tutorial.

Loop-Antenna Calibration

Loop-antenna calibration is discussed in this tutorial. Loop antennas are especially used in low-frequency radiated-emission (RE) and radiated-susceptibility (RS) measurements and tests. These are important in commercial systems, but critical in military systems. The standards used for this purpose are reviewed, and comparisons among them are made. Results are presented with commercial as well as home-made loop antennas.

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.

Alternative conducted emission measurements on mains without LISNs

Conducted emission tests are always performed by the use of LISNs in laboratories in accordance with CISPR22, CISPR11 and other similar standards. However, it is not always possible to use LISNs because of some limitations. If the EUT (Equipment Under Test) has large dimensions or high currents, it is not, for most of the time, possible to send it to an EMC laboratory or to use LISNs during the test. As a consequence, usage or development of alternative conducted emission test methods is inevitable in industry. In this paper, we made conducted measurements on actual EUTs in alternative environments whose impedances are different from the standard LISN impedance and continued to establish the fundamentals of alternative conducted emission tests based on the impedance measurements of the EUT, supply and used cables. We also established the correlation, on the basis of impedance measurements, between these alternative conducted emission test method and the reference conducted emission test method.

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.