1,720,965 research outputs found
Acoustic Wave-Based Wireless Data Communication in Urban Water Supply Networks
Get PDFL'abstract è presente nell'allegato / the abstract is in the attachmen
Investigation on the Susceptibility to EMI of Second-Order ΔΣ Modulators
Get PDFThis paper analyzes the effects of radio frequency interference
on second order ΔΣ modulators based on continuoustime
(CT) and on discrete-time (DT) architectures. Specifically,
Modulators used for the acquisition of sensor signals are targeted,
which can operate with moderate clock rates due to the relatively
small bandwidth of the signal to be acquired. A continuous
wave interference with frequency above that of the modulator
clock signal is superimposed onto the nominal input one with
the purpose of evaluating the degradation of their performance,
and more specifically their capability to demodulate out of band
interference
On the Robustness of Discrete-Time and Continuous-Time ΣΔ Modulators to Conducted RFI
No full textSigma-Delta Analog-to-Digital Converters (ADCs) are widely adopted in sensor signal acquisition circuits for their ability to achieve high resolution with minimal hardware complexity. The heart of these ADCs is the modulator, which can be implemented using either continuous time (CT) or discrete time (DT) techniques. While DT modulators are typically preferred due to their robustness against nonidealities, their immunity to external noise, particularly from radiofrequency (RF) interference when integrated with noisy circuit blocks like RF transceivers, becomes crucial for overall system performance. In this article, the impact of RF interference on the operation of second-order DT and CT modulators is investigated, employing approximated analytical techniques and computer simulations. Moreover, direct power injection experimental tests have been carried out, and the measurement results provide an immunity comparison between the two modulator types
EMI Reduction at the Source in WBG Inverters: A Comparative Study of Spread-Spectrum Modulation and Auxiliary Switching Leg Techniques
No full textEffective electromagnetic interference (EMI) filters are required by switching converters to comply with conducted emission regulations. However, these filters often pose significant challenges, being expensive, bulky, and heavy. Such an issue is further aggravated with the latest generation of wide band gap (WBG)-based power converters. Reduction of the filter size can be achieved through conducted EMI mitigation techniques that address emissions at the source, particularly at low frequencies. Spread-spectrum modulation (SSM) has gained increasing interest to mitigate EMI, as it does not require any hardware alterations. This article investigates the effectiveness of the SSM in case of WBG traction inverters, where the switching frequency remains in the tens of kilohertz. In addition, the use of an additional switching leg to reduce the EMI was also investigated. A comparative analysis of these two techniques and their effectiveness in the common mode (CM) conducted EMI suppression is carried out. Experimental results are provided demonstrating the feasible CM conducted EMI reduction. It was found that the EMI peak at 160 kHz decreased by 2 dB in the SSM case and by 25 dB in the additional leg case
Metodo di trasmissione e ricezione di dati mediante trasmissione di segnali acustici in un fluido di una condotta, impianto e ricetrasmettitore per l’attuazione del detto metodo
No full textA Critical Analysis of Amplifier Requirements in Capacitance-Boosting Circuits for EMI Reduction
No full textThis work presents a critical analysis of the amplifier requirements for capacitance-boosting circuits, like those used in active EMI filters. The relationship between the amplifier specifications and the overall performance of these circuits is investigated. The study begins with an overview of the fundamental principles of capacitance-boosting circuits,
followed by an in-depth exploration of the role of amplifiers in these systems. Then, various amplifier parameters such
as bandwidth, output impedance, and output swing are critically analyzed, highlighting their impact on the
performance of capacitance-boosting circuits. Through rigorous theoretical analysis and computer simulations, this
work provides valuable insights into the optimal amplifier requirements for capacitance-boosting circuits
Experimental Characterization of In-Pipe Acoustic Communication Channels Through Measurement of Pressure Transfer Functions
Get PDFCommunication systems based on in-pipe acoustic propagation have great potential to cover areas in which traditional infrastructure is unavailable. Characterization of the channel plays an important role in the design of any communication system. However, in case of spatially large channels, this aspect needs further investigations. In the present work, a method for
the characterization of an acoustic channel is presented. This is based on the measurement of the complex transfer functions relating voltages and pressures at the channel ports. Such a technique was validated on a 75m long segment of a urban water distribution pipeline. The measurements assessed the frequency selectivity of the acoustic channel and the wave propagation speed. From experimental results, the response of the acoustic channel had an overall low-pass behavior, but it showed several
deep notches at low frequency
New Challenges on the Electromagnetic Compatibility of Electric Vehicles
No full textThe massive use of electronics in modern electric vehicles poses new challenges to the coexistence of electric power units, analog and digital sensors and vehicle-to-infrastructure (v2i) communication systems. Indeed, power units like traction inverters or DC-DC converters have constantly improved over time in terms of power density and efficiency. However, this has led to increase the electromagnetic interference (EMI) they generate. In addition, the need of high capacity wireless and wired communication channels and the use of radars has increased the number of on board radio frequency and mm wave transmitters, which increase the level of electromagnetic pollution as well. Clearly, this renewed scenario poses new challenges to reduce the emission and increase the immunity to EMI of on board electronic units.
In this context, the μEMC group has development some techniques aimed to reduce the electromagnetic emission generated by power modules, thus reducing the size of the EMI filters. For instance, it has been shown that a fine alignment of complementary switching voltages (see Fig. 1(a),(b)) reduces the conducted emission at low frequency (150kHz - 10MHz) significantly, as highlighted by the plot in Fig. 1(c) [1].
The group has also proposed solutions aimed to damp the oscillations resulting from fast switching based on resonant snubbers or active gate drivers [2,3]. For instance, the solution proposed in [3] allows one to damp the voltage oscillations triggered by hard switching at high frequency, as highlighted in Fig. 2.
Regarding the immunity to EMI of analog front-end, since A/D converters based on ΣΔ modulation are increasingly used for signal conditioning, a study on the susceptibility of modulators [4] has been performed. Two second-order modulators have been considered, and the performance of Continuous-Time (CT) and Discrete-Time (DT) loops has been compared. Simulations have been carried out in different amplitude and frequency injection conditions showing that the DT modulator can be highly susceptible to RFI, resulting in a large offset voltage, as shown in Fig. 3(a). CT modulators showed to be more resilient to RFI, presenting a smaller offset voltage. However, spectral analysis showed even-order harmonic distortion in the presence of low frequency disturbances, as shown in Fig. 3(b)
A Comparison of Spread Spectrum and Sigma Delta Modulations to Mitigate Conducted EMI in GaN-Based DC-DC Converters
Get PDFGaN power transistors offer significant advantages
with respect to Si ones, but introduce challenges in meeting EMC
regulations due to their high switching frequencies. This paper
compares two modulation schemes, Spread-Spectrum Modula-
tion (SSM) and Sigma-Delta Modulation (Σ∆M), for reducing
the conducted Electromagnetic Interference (EMI) delivered by
GaN-based DC-DC converters. The study analyzes how these
techniques impact converter performance and evaluates their
effectiveness in reducing conducted EMI at low frequencies. The
findings provide valuable insights for designers seeking the most effective strategy for EMI mitigation
Volume Reduction of Traction Power Inverter EMI Filter Based on Mitigation Techniques at the Source
Get PDFSwitching converters require effective EMI filters to comply with conducted emission regulations. However, these
filters often pose significant challenges, being expensive, bulky and heavy. The situation is further exacerbated with the latest generation of converters, utilizing WBG semiconductor devices, which operate at higher switching frequencies. Reduction of the filter size can be achieved through conducted EMI mitigation techniques that address emissions at the source, particularly at low frequencies. This paper analyzes the CM filter volume reduction when using two CM mitigation techniques acting at the source, namely Spread Spectrum Modulation (SSM) and the Delay Compensation Technique (DCT). The considered techniques are implemented on a WBG traction power inverter and the volume reduction of the CM EMI filter is evaluated through computer simulations
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