Tecnica di Sommazione Fasoriale per la Misura della Risposta in Frequenza alle Basse Frequenze

In this technical paper, a measurement system for the frequency response measurement, in amplitude and phase, is shown. The system is based on the phasorial sum, and it operates in the frequency range from 10 Hz to 100 KHz. The phase is achieved by the amplitudes of the input and output voltages and by their phasorial sum; the phase sign is achieved by an electronic circuit, which is realized by a delay-type flip-flop. The system is controlled by a software, so that the input and output voltages of the device under test and their phasorial sum are sequentially measured by a switch and a digital voltmeter. Some meaningful measurements and simulations confirm the soundness of the proposed system

On the Evaluation of the Shielding Effectiveness of an Electrically Large Enclosure

The shielding effectiveness (SE) has become a fundamental step in testing active or passive electric devices. The Reverberating Chamber (RC) is a well- established method for determining the SE since has the advantage to expose the material to a more realistic environment. In this paper the SEe of electrically large enclosures with a metallic mesh grid in a RC is evaluated. Enclosures made with metallic mesh are considered. In particular, it is shown that the SE of a material is unable to provide complete information for the SEe of an electrically large enclosure made with the same material. Moreover, this latter one is related to the loading conditions within the enclosure itself. Measurements accomplished at RC of the Università di Napoli Parthenope (formerly Istituto Universitario Navale, IUN) confirm the physical soundness of the proposed approach

Base-case model for measurement uncertainty in a reverberation chamber including frequency stirring

We address the uncertainty of reverberation chamber (RC) measurements in presence of both mechanical and frequency stirring (FS). A base-case model is derived for reverberation fields affected by the measurement uncertainty due to the lack of a perfect statistical uniformity of fields in a RC. It is found that the measurement uncertainty associated with the FS depends on both the total uncorrelated samples and the local insertion loss (IL). The local IL depends on the frequency stirring bandwidth (FSB). The model allows us for obtaining separate measurement uncertainty contributions. Measurements support the achieved uncertainty model. In particular, results show that the dependence on the IL is normally rather weak also when very wide FSBs are used

On the Shielding Effectiveness Calculation of Enclosures Through Measurements in Reverberation Chambers

The IEC 61000-4-21 and IEEE 299.1 documents report similar but not equal procedures to measure the shielding effectiveness (SE) of enclosures through the use of reverberation chambers. In this article, it is shown that these two measurement procedures can be merged in a single, enhanced, one. In particular, it is shown that the evaluation of the SE of enclosure in Annex H of IEC 61000-4-21, which exploits only mechanical stirring, can be improved by using the hybrid stirring, which includes also the frequency stirring, thus increasing the number of uncorrelated samples. On the other hand, it is shown that at low frequencies the evaluation of the SE of enclosures based on the definition in IEEE 299.1 can be improved through the use of the maximum values of measured powers rather than the average ones. The single, enhanced, proposed procedure provides more prudent SE values than the two standards at the low frequencies, especially for standard IEEE 299.1. The presented measurement approach is supported by results obtained in three different laboratories

A theory of alternative methods for measurements of absorption cross section and antenna radiation efficiency using nested and contiguous reverberation chambers

Average ACS can be measured in a reverberation chamber; however, the existing technique determines a value that includes the effects of the radiation efficiencies of the antennas used in the measurement. Correcting for these necessitates further complex measurements. Here we present the theory of an alternative measurement methodology using two nested or contiguous reverberation chambers which is free from errors caused by the radiation efficiencies of the antennas. The new method is based on the theoretical average transmission cross sections (TCSs) of circular holes in a metal plate between the two chambers. In fact the method can be viewed as an accurate transfer calibration measurement between TCS and ACS that is independent of both the chamber and antenna characteristics. Further, since the existing method of measuring ACS includes the effects of the radiation efficiencies of the antennas, a comparison of the ACS of a reference object, measured using both the existing and new methods, also provides an alternative method of determining radiation antenna efficiency. Measurement uncertainties for both alternative measurement methods – ACS and antenna radiation efficiency – are also derived

Calcolo delle Perdite Elettromagnetiche nelle Pareti delle Camere Riverberanti

In this paper will be computed the model for the electromagnetic losses in a metallic slab placed in an environment where the radiation is isotropic and quasi-monochromatic. Such a model will be applied at the losses in the walls of the reverberation chambers and to express their quality factor Q, with a special success at the highest frequencies

Probability Density Function of the Quality Factor for Reverberation Chambers Operating With Hybrid Stirring Including Frequency Stirring

we deal with the probability density function (PDF) for the quality factor Q of reverberation chambers operating with combined mechanical and frequency stirring techniques. It will be shown the Q PDF of step-tuned and mode-stirred reverberation chambers (RCs), respectively, where the mechanical and frequency stirring are combined, and how it is affected by the width of the frequency sweep. The results for source-stirred RCs, where the frequency stirring is combined with source stirring, are implicitly obtained as well. By the results, possible effects on the measurements due to combinations of stirring techniques, including the frequency stirring, are also shown