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Probes fabricated using multi-layer process are proposed for complex permittivity measurements in microwave frequency range. For multi-layer processing, we have considered LTCC(Low Temperature C O -M Ceramic)and MEMS(Micr0-Electro-Mechanical-Systems) processes to make the probe smaller and thus to be applicable to small biological tissues. We expect the probe size can be reduced to 0.1" by 0.2" if necessary. We also investigate the shielding effect of vias that is normally used to support TEM wave inside the planar transmission line structure. The complex permittivity of 0.9% saline in microwave frequency range(lOOMHz40GHz) was measured using MEMS and LTCC probe to verify the usefulness of the proposed probes.Index Terms -Permittivity measurement, permittivity of biological tissues, MEMS probe, LTCC probe

This paper describes the application of a passive noise cancellation method to a prototype inductor-inductor-capacitor (LLC) resonant converter by placing a compensation winding in a transformer to reduce common mode noise. The connection method for the compensation winding is investigated. A circuit analysis is implemented for the displacement currents between the primary and secondary windings in the transformer. The analyzed displacement currents are verified by performing a circuit simulation and a proper compensation winding connection that reduces common mode noise is found. The measurement results show that common mode noise is reduced effectively up to 20 dB in the 1 to 7 MHz frequency region for the prototype LLC resonant converter by using the proposed passive noise cancellation method. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ⓒ

A common-mode (CM) active filter was designed in a compact package to suppress CM conducted emission at a switching mode power supply. A very compact structure was implemented in the voltage-sense voltage-compensation feedforward topology. The proposed filter was analyzed, and a prototype was applied to a real switching mode power supply (SMPS) board, demonstrating its usefulness by experiments.