Figure 6 - uploaded by Mikko Kuisma
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Measured spectrogram of the frequency-hopping test signal. Horizontal axis is frequency from 0 Hz to 1 MHz, time in vertical axis. The amplitude unit is in dBm. Spectrogram shows the periodicity and the change in instantaneous frequency of the hopping sequence.
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Spread-spectrum techniques have raised their importance as a common EMI-reduction technique in power supplies. Ability to track and measure such a signal is vital. Analysis and synthesis of an effective spread-spectrum sequence is also important. Pulse-type and apparently random interference are other types of signals which are hard to detect and m...
Contexts in source publication
Context 1
... screenshot from WCA 330 is presented in Fig. 6. The signal in this example is a frequency-hopping signal generated with Matlab TM . The EMI-spectrum of the same signal was also measured with a conventional EMI-test receiver, Fig. 5. Although the fundamental frequency and about six harmonic components of the hopping signal can be seen in Fig. 5, almost nothing else can be said about ...
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... signal generated with Matlab TM . The EMI-spectrum of the same signal was also measured with a conventional EMI-test receiver, Fig. 5. Although the fundamental frequency and about six harmonic components of the hopping signal can be seen in Fig. 5, almost nothing else can be said about the hopping sequence. Measured spectrogram presented in Fig. 6 exposes the hopping sequence, duration of one hopping interval and harmonic content of the signal. Another measured example is shown in Fig. 8 and 9. Periodic pulsed signal and the burst period of 9.2 ms can be seen in the spectrogram, Fig. 9. The shape of the EMI- spectrum measured with R&S ESI-40 test receiver, Fig. 8, is almost the ...
Context 3
... screenshot from WCA 330 is presented in Fig. 6. The signal in this example is a frequency-hopping signal generated with Matlab TM . The EMI-spectrum of the same signal was also measured with a conventional EMI-test receiver, Fig. 5. Although the fundamental frequency and about six harmonic components of the hopping signal can be seen in Fig. 5, almost nothing else can be said about the hopping sequence. Measured spectrogram presented in Fig. 6 exposes the hopping sequence, duration of one hopping interval and harmonic content of the signal. Another measured example is shown in Fig. 8 and 9. Periodic pulsed signal and the burst period of 9.2 ms can be seen in the spectrogram, Fig. 9. The shape of the EMI- spectrum measured with R&S ESI-40 test receiver, Fig. 8, is almost the same if compared to the previous example and nothing can be said about the bursts, which are clearly present in the measured ...
Context 4
... screenshot from WCA 330 is presented in Fig. 6. The signal in this example is a frequency-hopping signal generated with Matlab TM . The EMI-spectrum of the same signal was also measured with a conventional EMI-test receiver, Fig. 5. Although the fundamental frequency and about six harmonic components of the hopping signal can be seen in Fig. 5, almost nothing else can be said about the hopping sequence. Measured spectrogram presented in Fig. 6 exposes the hopping sequence, duration of one hopping interval and harmonic content of the signal. Another measured example is shown in Fig. 8 and 9. Periodic pulsed signal and the burst period of 9.2 ms can be seen in the spectrogram, Fig. 9. The shape of the EMI- spectrum measured with R&S ESI-40 test receiver, Fig. 8, is almost the same if compared to the previous example and nothing can be said about the bursts, which are clearly present in the measured ...
Citations
... Failure detection of integrated circuits (ICs) using thermal techniques has been well studied for a long time [3], [4], it has also been used to detect latch-up [5]. The time-frequency analysis has been shown to be a powerful tool for electromagnetic interference (EMI) failure analysis [6], [7]. The detection methods discussed in the other literature mainly focus on the bit error by monitoring the I/O of IC for an incomplete system without user interface, or the soft failure can be observed directly from the user interface. ...
Electrostatic discharge (ESD)-induced soft failures are a critical issue for electronic systems as the failures are mostly found after the hardware design is completed. Any changes applied to the hardware may delay the project. Diagnostic tools capable of identifying soft failure-induced malfunctions in an early stage of product design help to reduce the risk of late stage ESD-induced project delays. In many cases, soft failures can be directly observed by the user interface, system crash, or other obvious indicators. However, in an early product design stage the operation system may be marginal and applications may not be available. To improve the ability to detect soft failure critical design choices, this paper presents several methods to identify ESD-induced changes which may not be observable via direct observation. These methods include the observation of ac or dc currents, monitoring dc voltages, capturing near fields and processing them via short-term fast fourier transform (FFT), wavelet transformation, down mixing to audible range, and monitoring for latch-up via thermal imaging. The paper introduces the basis of each method, shows examples, and compares them for their detection ability.
... On the other hand, wide windows generate poor time resolution but a better frequency resolution. However, the wider windows violate the stationary conditions [119]. ...
The focal and non-focal epilepsy is seen to be a chronic neurological brain disorder, which has affected
$\approx ~60$
million people in the world. Hence, an early detection of the focal epileptic seizures can be carried out using the EEG signals, which act as a helpful tool for early diagnosis of epilepsy. Several EEG-based approaches have been proposed and developed to understand the underlying characteristics of the epileptic seizures. Despite the fact that the early results were positive, the proposed techniques cannot generate reproducible results and lack a statistical validation, which has led to doubts regarding the presence of the pre-ictal state. Various methodical and algorithmic studies have indicated that the transition to an ictal state is not a random process, and the build-up can lead to epileptic seizures. This study reviews many recently-proposed algorithms for detecting the focal epileptic seizures. Generally, the techniques developed for detecting the epileptic seizures were based on tensors, entropy, empirical mode decomposition, wavelet transform and dynamic analysis. The existing algorithms were compared and the need for implementing a practical and reliable new algorithm is highlighted. The research regarding the epileptic seizure detection research is more focused on the development of precise and non-invasive techniques for rapid and reliable diagnosis. Finally, the researchers noted that all the methods that were developed for epileptic seizure detection lacks standardization, which hinders the homogeneous comparison of the detector performance.
... This study applies a time and frequency mixed-domain analysis to measure and characterize EMI noise. The short-time fast Fourier transform (STFT) is used[8,9]. The resulting STFT (called a " spectrogram " ) can visualize both the frequency and time behaviors of the signal[8,9]. ...
... The short-time fast Fourier transform (STFT) is used[8,9]. The resulting STFT (called a " spectrogram " ) can visualize both the frequency and time behaviors of the signal[8,9]. A mixed-domain oscilloscope was triggeredon the diode current and simultaneously captured a frequency spectrum of v a during the diode switching operation.Fig. ...
Electromagnetic interference (EMI) noise in time and frequency mixed domains is analyzed to understand the influence of noise source behavior on the conducted emissions in boost converters. The switching characteristics of a sillicon PiN diode and a sillicon carbide Schottky barrier diode in a boost converter are compared and evaluated as EMI noise sources, and the influence of diode switching operation on the generation and attenuation of conducted emissions are discussed on the basis of spectrogram analysis.
... In this case, the time resolution was set to 4 µs, and the frequency resolution was set to 250 kHz. See [5][8] for further information on joint-time frequency domain techniques in EMI analysis. The STFFT analysis results shown inFig. ...
The evaluation of a product in terms of radiated emissions involves identifying the noise sources. Spectrum analyzer (SA) measurements alone are unable to identify noise sources when multiple sources are responsible for emissions at a particular frequency. In this paper, an approach using combined near-field and far-field measurements is proposed. This method consists of recording signals from a near field probe and from an antenna in the far-field using a high speed oscilloscope and analyzing the relationship between them via different post processing methods. The noise source can be identified by varying the location of near-field probe and searching for the probe signal that best correlates to the far field signal. A variety of post processing methods have been employed in this work. The short term fast Fourier transform (STFFT) is used to visualize the time dependence of the frequency content. Envelope correlation, coherence factor, and cross-correlation methods are further explained and tested for their ability to identify possible sources of emission problems.
The ringing oscillation in turn-off of diode may induce electromagnetic interference (EMI) noise especially in fast switching operation. This study compares static and dynamic characteristics of a Si PiN diode and three type SiC Schottky barrier diodes, which have comparable voltage and current ratings, and focuses on the influence of diode characteristics on conducted emission of the continuous current mode (CCM) DC-DC boost converter. The dynamic characteristics of diode current in turn-off operation are evaluated by Prony's method. The spectrogram of conducted emission is measured to understand how the noise source could affect the conducted noise emission.
The design process for home appliances is intrinsically driven by product information. The common workflow is usually pre-defined and not flexible. The most difficult part in the design of power electronic boards to be used in household appliances is abiding by the Electromagnetic Compatibility (EMC) regulations. EMC characteristics are difficult to determine in early design stages. In fact electromagnetic compatibility should be taken into account as well as electrical, thermal and mechanical issues. This paper proposes a model-based design tool which allows achieving good performances in term of EMC also in the early design stages. Trough this tool is possible to predict the EMC behavior of the generic power converter using a given modulation. Simulation result and experimental result are presented in this paper, showing a good match in the EMC improvements. The proposed tool is extremely flexible, and can be used proficiently in complex product design, especially in the conceptual design stage. The experimental results confirmed that the derived model can roughly predict EMI. To attenuate EMI in the prototype converter, spread spectrum is employed and its influence on EMI spectra is presented via measurement.
Limiting harmonics in the conducted noise of switch mode power supplies is very important, but finding the causes of harmonics to get the best solution to the electromagnetic interference (EMI) problem is often complex. A new tool for the search of conducted noise causes is presented: the more significant harmonics in the EMI receiver measurement are searched in the time evolution of the line impedance stabilization network (LISN) voltage by using the continuous wavelet transform (CWT). In the time frames where the harmonics are present, similar harmonic contents are searched for in the waveforms of the circuit, because these are the causes of the conducted noise. An example of application is described: signals of a boost PFC are processed in different ways to be compared to the EMI receiver measurements of LISN voltage spectrum. The CWT results match pretty well and give some further information than the Fourier transform does
Electromagnetic interference (EMI) remains one of the main problems in switch mode power supplies (SMPS). Various EMI reduction schemes for switching converters using switching modulation have been proposed over the last decades. These variable-frequency (VF) modulation techniques include quasi-random system clock generation, random or quasi-random modulation of the system clock frequency, frequency modulation (FM) of the system clock, sigma-delta modulation, chaotic peak current control and hysteresis control. Voltage and current ripple have been considered a major problem with VF-modulated power supplies. The analysis of input current in boost converter using VF modulation is presented in this paper.
