Hubert Trzaska

EMF probes calibration in a waveguide

This paper is devoted to an estimation of electromagnetic field probe calibration error, while the calibration is performed within a waveguide, due to the presence of conducting walls of the waveguide and their influence on the calibrated probes transmittance. The presented estimations and measurements are performed for symmetric dipole antennas of different slenderness ratios. However, the approach is applicable to any type of electromagnetic field (EMF) standard and design of field probes.

How to Measure in the Near Field and in the Far Field

A background of the electromagnetic field (EMF) measurements is presented in the work. A special attention is given to the specificity of the measurements performed in the Near Field. Factors, that should be taken into consideration as during the measurements as well during their analysis, are discussed. Without their understanding and considering a comparison of the measurements’ results, meters’ calibration and EMF standards comparison between different centers is impossible.

Methods of the electromagnetic fields intensity level assessment and monitoring in the environment

The paper contains review of electromagnetic field (EMF) sources from the environmental point of view. It shows the simplest methods of EMF measurement and differences between selective and broadband measurements listing its advantages and disadvantages, what is essential for the EMF assessment for the need of monitoring in the environment. The measurement possibilities are also one of the subject taken up in this work. Authors point an important aspect of EMF evaluation which is field intensity changeability in time (periodicity) characteristic for mobile telephony systems related with the subscribers daily activity.

EMF meters for surveying purposes calibration and validation

The work presents selected problems of calibration, testing and checking the electromagnetic field (EMF) meters and probes designated mainly for measurements in the near-field. The metrology is related to surveying labor safety and environment protection against unwanted exposure to the EMF.

Non-stationary EMF surveying accuracy improvement

The paper discusses accuracy of non-stationary EMF measurements. The accuracy is mainly limited by applied methods of meters calibration. New method of calibration is presented. The method allows a limitation of the calibration inaccuracy to level of ±1dB.

Primary and Secondary EMF Standards

EMF measurements are one of the least accurate within the metrology of physical magnitudes. While many of the latter, for instance frequency, are measured with inaccuracy below e-10, in the case of the former the inaccuracy on the level of 1 dB is as accepted as the best, but only in the case of the far field measurements and inaccuracy on the level of 3 dB, or even 6 dB in the near field measurements is very of the to be accepted. Apart from other factors limiting accuracy of the measurement one of the most important of them is inaccuracy (class) of the EMF standards applied for their calibration. The activities in the field of EMF standards are presented

Radiations from a portable terminal

The paper shows wide range of radiations from handy-talkie type devices. The complex exposure of an operator should be taken into account in biomedical studies, while only role of a carrier wave is investigated.

Exposure systems for bioelectromagnetic experiments

Abstract One of the most interesting questions in bioelectromagnetics is why there is a difference between results of experiments performed in various labs in “identical” conditions. One of the possible reasons is the difference of investigated objects, especially while performing experiments in vivo. However, the authors, as engineers, would like to focus readers’ attention on the technical aspects of exposure systems, especially the presence and role of mutual interaction between biological objects under test (OUT) and the exposure system, the interactions between the objects, the role of polarization, the similarity of real exposure to that applied in experiments etc. All these factors may alter the results of experiments and lead to false conclusions.

Methods of the standard EMF generation

The previous chapter referred to two calibration methods: the standard transmitting antenna method (STA) or standard field method, and standard receiving antenna method (SRA) or substitution method. Lets characterize them briefly. 1. The STA method is based upon EMF generation with the use of a transmitting antenna whose parameters (radiation pattern, efficiency) are known to a required accuracy and established either theoretically or experimentally. The EMF at an observation point is calculated taking into account the parameters of the antenna, its excitation, and the geometry of propagation. 2. The SRA method requires a receiving antenna of well-known parameters and a system that makes it possible to measure current in the antenna or the voltage at its input. The SRA is placed in an EMF generated by an arbitrary source and then replaced by an antenna (meter, probe, device) under test. Two assumptions are made in this procedure: the EMF is stable enough to not change during the replacement, the antenna under test is immersed in the same field as the SRA and makes identical EMF deformations to the SRA. In the previous discussions we took into account EMF standards with dipole or loop antennas. However, an almost identical approach may be adopted when other types of standards are in use. For instance, in guided wave standards, the EMF is established on the ground of excitation measurement of a system of known parameters, which is similar to the standard field method. In the case of different types of chambers the substitution method is more appropriate.

Accuracy analysis of the standards with horn antennas

The accuracy of the power gain and the effective area of the horn antenna are of primary importance for the class of the EMF standard in which the antenna is applied. Horn antenna work above 1 GHz frequency range. Horn antennas are usually fed from a waveguide; the simplest “horn antenna”is an open end of a waveguide. Possible estimation errors and measurements are discussed in this chapter.