The paper describes a methodology for an efficient design of novel products based on magneto-dielectric (ferrite) materials with desirable frequency responses that satisfy EMC and SI requirements. The methodology starts from estimating complex permittivity and permeability of these materials. This requires measurement techniques, approximation resultant frequency characteristics for permittivity and permeability using a curve-fitting procedure, and development of a full-wave numerical simulation tool that could deal with frequencydispersive materials. An example of a ferrite material measurement, constitutive parameters extraction using a genetic algorithm, and corresponding FDTD modeling over the frequency range from 10 to 500 MHz is provided.
An RLC model of ferrite chokes for suppressing common-mode (CM) currents is presented. The equivalent lumped-element circuit parameters are obtained from the frequency-dependent input impedance of a ferrite choke on a wire above the ground plane. This input impedance can be either measured (using vector network analyzer or impedance analyzer), or numerically modeled based on the known ferrite material properties (permittivity and permeability). An example of using both numerical modeling and measurements is provided. Results show good agreement at comparatively low frequencies (below 200 MHz). The upper frequency limit for the proposed equivalent lumped-circuit model is discussed.
The basic theory of radio broadcasting is discussed from an experimental point of view. First, concepts like wave modulation and tuning are explained with the use of instruments in the physics laboratory. Then, a very basic radio receiver is described and assembled, whose most important feature, like in the old 'crystal radios', is the absence of a power supply. Even if the underlying general concepts are usually described in general physics classes at high school and university, for students this setup is a practical example of the application of electromagnetic waves.
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