Mohd Hafiz Baharuddin

Challenges of time domain measurement of field-field correlation for complex PCBs

Measurements of field-field correlation in the time domain can be used to characterize stochastic broadband emissions from complex sources. A two-probe scanning measurement system is developed and used to sample the stochastic emissions in the near-field of two such sources: a reverberation chamber with a rectangular aperture and a generic printed circuit board (PCB). We show that measured field data can be utilized in numerical wave propagation schemes to predict the stochastic fields in and radiated from a packaged device.

Wigner-Function-Based Propagation of Stochastic Field Emissions From Planar Electromagnetic Sources

Modeling the electromagnetic radiation from modern digital systems—acting effectively as extended stochastic sources as part of a complex architecture—is a challenging task. We follow an approach here based on measuring and propagating field-field autocorrelation functions (ACFs) after suitable averaging. From the modeling side, we use the Wigner transform of the ACFs to describe random wave fields in terms of position and direction of propagation variables. An approximate propagator for the components of the radiated magnetic field is constructed for these ACFs based on a linear flow map. Field-field ACFs at the aperture level are obtained from scanning measurements of complex sources. Distance and spatial resolution of the scanning plane is less than a wavelength from the source plane to capture the imprint of evanescent waves in the near-field ACFs. Near-field scanning and efficient near-to-far-field propagation is carried out and compared with measurements. Results of this study will be useful to assist far-field predictions, source reconstruction, and emission source microscopy.

Near-Field Scanning and Propagation of Correlated Low-Frequency Radiated Emissions

Electromagnetic radiation from complex printed circuit boards can occur over a broad frequency bandwidth, ranging from hundreds of megahertz to tens of gigahertz. This is becoming a critical issue for assessment of EMC and interoperability as electronic components become more and more integrated. We use emissions from an enclosure with a single-slot aperture and equipped with operating electronics to exemplify and model such sources. Spatial correlation functions obtained from two-probe measurements are used both to characterize the source and to propagate the emissions. We examine emissions in the submicrowave frequency range, where evanescent decay dominates the measured correlation function at the distances measured. We find that an approximate, diffusion-like propagator describes the measured emissions well. A phase-space approach based on Wigner functions is exploited to develop this approximation and to provide enhanced understanding of the emissions.

Characterization of EM field above a single aperture or air-vents of an enclosure for a variable degree of correlation between stochastic sources inside

In this paper, an electromagnetic field distribution above a single aperture or an array of apertures (so-called air-vent) of a metal enclosure with two monopole sources inside is considered. Based on the previously developed approach that uses the S-parameter description of a multi-port network model of sources and near-field probes, incorporated into the correlation matrix calculation, the electromagnetic field above the aperture is characterized for a variable degree of correlation between considered sources. Height at which the aperture field is sampled and the type of aperture on enclosure lid are also taken into account. Experimental and numerical data have accompanied the analysis carried out in the paper.

Reducing the complexity of near-field scanning of stochastic fields

Near-field scanning is an established technique for the efficient and accurate measurement of the radiated emissions from antenna or electronic equipment for EMC studies. Recently the use of two probes near-field scanning of the correlation of the radiated fields has been developed for the measurement of electronic equipment with many uncorrelated distributed sources whose emissions are essentially stochastic. However, it has been found that the use of two probe scanning is very time consuming and requires large computer resources in terms of memory and processing power. In this paper methods for reducing the measurements for the characterisation of complex electronic devices is examined through the study of a typical electronic device. It is shown that without any a priory knowledge of the device under test it is difficult to reduce the measurement burden.