Computational Electromagnetics: A Miscellany

The paper presents a miscellany of unorthodox and, in some cases, paradoxical or controversial items related to computational and applied electromagnetics. The topics include a definition of the magnetic source field via a line integral, losses in electric power transmission vs. losses in photonics, homogenization of periodic electromagnetic structures, spurious modes, models of plasmonic media, and more. It is hoped that this assortment of subjects will be of interest to a broad audience of scientists and engineers.

The Effect of the Ionosphere on the Controlled-Source Field in the Frequency Range between 0.4 and 95 Hz

The paper addresses the effect of the ionosphere on the ELF and lower frequency waves excited in the Earth-ionosphere waveguide by a controlled source. The experiment carried out on the Kola Peninsula is described and the results of measurements in the frequency range 0.4–95 Hz are presented. Non-monotonic behavior of the magnetic field with time is revealed. It is shown that variations in the magnetic field are related to the state of the ionosphere and depend on the geomagnetic activity. The importance of the effect of the topside ionosphere on the structure of the studied field is discussed.

The Effect of the Ionosphere on the Controlled-Source Field in the Frequency Range between 0.4 and 95 Hz

The paper addresses the effect of the ionosphere on the ELF and lower frequency waves excited in the Earth-ionosphere waveguide by a controlled source. The experiment carried out on the Kola Peninsula is described and the results of measurements in the frequency range 0.4–95 Hz are presented. Non-monotonic behavior of the magnetic field with time is revealed. It is shown that variations in the magnetic field are related to the state of the ionosphere and depend on the geomagnetic activity. The importance of the effect of the topside ionosphere on the structure of the studied field is discussed.

Optimization of underdetermined hologram points in reconstructing the vibro-acoustic source field based on ESM

The distribution of measurement points is important in reconstructing the vibro-acoustic source field using the near-field acoustical holography (NAH) based on the equivalent source method (ESM). Because too close measurement impose a limit in the implementation of ESM, an optimal arrangement of the hologram data is needed to enable a longer distance measurement although the points are still within the near field. In this work, the optimal measurement positions are determined by adopting the method that assures the independence among the measuring positions as far as possible. Singular value decomposition of the transfer matrix is employed in the loop-iteration calculation fashion, in which the candidate measuring point affecting the increase of singularity is eliminated at each iteration step. Comparison is made with the uniformly distributed hologram points, the monopole version of ESM model, and the patch holography method. The test results reveal that the acoustic field of sound sources can be reconstructed meaningfully from the optimized hologram points of underdetermined condition. Under the predetermined reconstruction accuracy, the test results varying the hologram distance show that it is possible to realize the underdetermined far-distance measurement than the usual NAH.

A Novel Superjunction MOSFET with Ultralow Reverse Recovery Charge and Low Switching Loss

A novel superjunction MOSFET (SJ-MOSFET) for ultralow reverse recovery charge (Q RR ) and low switching loss is proposed and investigated. This device features a P-type Schottky diode and a source field-plate. The P-type Schottky diode consists of Schottky contact and P-base, which is reverse series-connected with body P-N junction diode. And the source field-plate is formed by implementing a polysilicon field-plate electrically coupled to the source, which is on the top of N-pillar. During the reverse conduction state, the P-type Schottky diode is reverse biased, which dramatically suppresses minority carriers injecting into the drift region. Simultaneously, electron accumulation layer formed under the source field-plate, which provides a path for the reverse current. Consequently, compared with the conventional SJ-MOSFET (Conv-SJ-MOSFET), the proposed SJ-MOSFET achieves an 84.0% lower Q RR with almost no sacrifice in other characteristics. Moreover, the proposed device also exhibits 47.4% and 66.0% lower gate charge (Q G ) and gate to drain charge (Q GD ), respectively. The significantly reduced Q G , Q GD , and Q RR contribute to an overall improvement in switching losses and resultant over 54.8% decrease in total power losses with operation frequency higher than 50 kHz, demonstrating great potential of the proposed SJ-MOSFET used in power conversion systems.