311 research outputs found
EMI Analysis Methods for Synchronous Buck Converter EMI Root Cause Analysis
DC/DC synchronous buck converters cause broadband emissions. A variety of methods are applied to analyze the root cause of the EMI. Time-domain voltage measurement and joint-time-frequency analysis allows to determine the location of the noise source. The near field scan reveals the current paths, and impedance measurement and 3D modeling can be used for further analysis of the noise source. A dual port TEM cell allows to distinguish E from H field coupling, This paper shows the application of those methods to a synchronous buck converter and reveals the sources of EMI leading to advice on the optimal PCB design. Finally, an innovative method of using a TEM cell measurement to predict the maximum possible radiated emissions is introduced
750 MHz radio frequency quadrupole with trapezoidal vanes for carbon ion therapy
High-frequency linear accelerators are very suitable for carbon ion therapy,
thanks to the reduced operational costs and the high beam quality with respect
to synchrotrons, which are presently the only available technology for this
application. In the framework of the development of a new linac for carbon ion
therapy, this article describes the design of a compact 750 MHz Radio Frequency
Quadrupole (RFQ) with trapezoidal vanes. A new semi-analytic approach to design
the trapezoidal-vane RFQ is introduced together with the relevant beam dynamics
properties. The RFQ is split into two decoupled rf cavities, both of which make
use of a novel dipole detuning technique by means of length adjustment. The
splitting is described both from the rf and the beam dynamics point of view.
The paper concludes with the rf design of the full structure, including maximum
surface field and thermal studies.Comment: Revised version published in Physical Review Accelerators and Beams
on 31 December 202
Perturbation theorems for Hele-Shaw flows and their applications
In this work, we give a perturbation theorem for strong polynomial solutions
to the zero surface tension Hele-Shaw equation driven by injection or suction,
so called the Polubarinova-Galin equation. This theorem enables us to explore
properties of solutions with initial functions close to but are not polynomial.
Applications of this theorem are given in the suction or injection case. In the
former case, we show that if the initial domain is close to a disk, most of
fluid will be sucked before the strong solution blows up. In the later case, we
obtain precise large-time rescaling behaviors for large data to Hele-Shaw flows
in terms of invariant Richardson complex moments. This rescaling behavior
result generalizes a recent result regarding large-time rescaling behavior for
small data in terms of moments. As a byproduct of a theorem in this paper, a
short proof of existence and uniqueness of strong solutions to the
Polubarinova-Galin equation is given.Comment: 25 page
Anticipating Vehicle-Level EMI using a Multi-Step Approach
A multi-step procedure for anticipating vehicle-level EMI is proposed in this paper. This approach uses multi-conductor transmission line (MTL) modeling to calculate current distributions along the cable bundle. A common-mode circuit is extracted from the MTL modeling, and is employed in full-vehicle full-wave modeling to determine radiation and interference. In this paper, mode-dispersion and mode-conversion phenomena are investigated, and the ambiguous definitions of the common-mode voltage and common-mode impedance are discussed
Anticipating EMI and On-Board Interference in Automotive Platforms
A dual-step MTL / FDTD strategy is proposed for anticipating full-vehicle level EMI. In the first step, the current distribution along a cable bundle connecting to electronic modules an an automotive platform is calculated using multi-conductor transmission-line (MTL) models. In order to account for common-mode discontinuities on the vehicle chassis, e.g., slots, 3D full-wave modeling (FDTD) is used to determine radiation impedances, which are thereafter incorporated in the MTL models for compensating the radiation power loss. In the second step, the obtained currents are implemented as impressed current sources in full-vehicle full-wave modeling using an FDTD multi-wire subcelluar algorithm. Thus, the full-vehicle emissions from the automotive harness and the common-mode discontinuities of the vehicle chassis can be predicted. The effectiveness and limitation of this approach have been demonstrated in a controlled laboratory environment
A Dual-current Method for Characterizing Common-Mode Loop Impedance
The definition of common-mode loop impedance is proposed instead of the ambiguous definition of common-mode impedance. Moreover, a non-invasive measurement method to characterize the common-mode loop impedance using dual clamp-on current probe is presented herein. The frequency responses of the current probes are de-embedded through a calibration procedure. Independent direct measurements using a network analyzer corroborate the validity of the Dual-Current-Probe Method
Complex maps without invariant densities
We consider complex polynomials for and
, and find some combinatorial types and values of such that
there is no invariant probability measure equivalent to conformal measure on
the Julia set. This holds for particular Fibonacci-like and Feigenbaum
combinatorial types when sufficiently large and also for a class of
`long-branched' maps of any critical order.Comment: Typos corrected, minor changes, principally to Section
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