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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.

In heterogeneous networks (HetNets), providing reliable and secure transmission uplinks to combat the potential interference is a major challenge. We address the multi-tier uplink interference issue, inspired by the secure waveform design in spatial and spectral domains to improve the system reliability and capacity. A system combining a beamforming (BF) technique based on uniform circle array and a frequency-hopping (FH) technique has been developed under an orthogonal frequency division multiplex (OFDM) scheme (i.e., OFDM/FH-BF system). The modified receiver structure is designed for the hopped multi-carrier signals. The convergence of the adaptive FH-BF system, which is critical for supporting highly mobile users in HetNets, is investigated. The combined effects of FH and BF techniques on system performance, in terms of output signal-to-interference-plus-noise ratio and bit-error-rate (BER), are fully studied. The simulation results show that the proposed OFDM/FH-BF system converges in a reasonably low number of snapshots, which meets the strict requirement for serving rapidly moving users. The combination of BF and FH techniques can offer reliable uplinks by mitigating the potential interference. In particular, at the cell edge with multiple interferers $K$ , the FH technique becomes the dominant anti-interference approach and the BER decreases with increasing size of the frequency slots set $q$ .

This paper discusses how the measurements of the near-field emissions in the time domain can be used to characterize the broadband emissions from complex sources such as multifunctional Printed Circuit Boards (PCBs). The near-fields, transverse to the measurement surface, are sufficient to characterise the radiator provided the surface contains all the significant fields. For time domain measurements, the field probe is calibrated over a broad bandwidth for both amplitude and phase to provide the probe impulse response. A suitable digital filter applied with the same probe impulse response to extract the time domain magnetic field data from the probe output voltage. Results show that good agreement in the can be obtained. The measured near fields can then be used to create an equivalent model of the PCB which can be used to predict the emissions in the far field or in any environment. In this work the objective is to create an equivalent time dependent dipole array model of the DUT.

The radiation from complex PCBs can be characterized through a statistical approach involving the field-field correlation. A two-probe measurement technique is developed to measure the stochastic electromagnetic (EM) emission from an Arduino Galileo board in an enclosure in the time domain at two different heights. The Wigner distribution function, which is a representation in phase space, is used to understand the mechanics of near field emissions. The evolution of the field-field correlation function and Wigner function is observed for both measurements. These results serve as a proof of principle for understanding that Wigner Function is a good candidate to understand whether the concept of radiation pattern can be extended to near field.

Emergent wireless telecommunications and 5G mobile networks will operate at very high frequencies, ranging from microwave (5GHz) to mmWave (28GHz and beyond) regimes. Indoor coverage is challenging at these frequencies, where environments are expected to be highly overmoded. We perform full-wave Transmission Line Matrix simulations of a test electromagnetic environment. For electrically large, multiply connected rooms with simple polygonal irregularities, e.g. blades, we show that different regimes occur in the spatial field pattern as the frequency increases. From 1 GHz to 5 GHz the pattern is speckled. At 8 and 12 GHz we observe the emergence of specular components existing on a noisy background. The statistics of fields in the background are important for small scale fading in non-line-of-sight conditions. We characterize the spatial statistics of the test environment. Because of coupling and partially regular boundary, fluctuations acquire non-generic features, and they result in non-Rayleigh distribution functions at the investigated frequencies. The resurgence of directionality in the high microwave regime has an effect in fading statistics in a similar way of shadowing, from which background field statistics are fitted by fat tail (Bessel K) distribution. However, since the transition from low to high microwave regimes has no defined separation between specular and noisy components, generated by reflection and diffraction, ray tracing algorithms — more appropriate to predict energy of specular components — need to be extended to cope with noisy fields. We envisage these methods to be fundamental in the description of mmWave propagation. The achieved results are useful to create channel models for the outdoor-to-indoor transition and to extend mobile signal coverage to indoor regions.