Abstract-An electromagnetic shielding of objects using ferrite-graphite composites is considered. The analytical model, using the Maxwell Garnett formulation for multiphase mixtures, results of computations based on this model and plane-wave formulation, and some experimental results are represented.
A method for an adequate visualization of a microwave intense noise spectrum envelope in a wide frequency range (several octaves), measurement of its power parameters, and detection of a narrow-band signal with unknown frequency and power against the noise background is presented. This method is based on an application of a nonheterodyne principle of microwave frequency (and power) conversion using a gyromagnetic converter, which operates in two regimes in turn: the resonance detection and the cross-multiplication. A block scheme and an operation of a two-channel measuring device combining the mentioned functions are discussed.
Abstract-In this paper, a number of physical phenomena taking place at the interaction of a crystallographically uniaxial ferrite resonator (UFR) with a semiconductor element, such as a Hall-effect transducer (HET), are analyzed. The UFR in this study is in a direct contact with an unpackaged HET. The interaction is studied in the vicinity of the ferromagnetic resonance in the UFR. The analytical model based on the combination of the problem of interaction of an arbitrarily orientated and shaped UFR with electromagnetic field of a multimode transmission line (waveguide) and thermal balance equations is proposed. A number of thermo/electro/magnetic phenomena that cause a voltage additional to that of the Hall-effect in the HET are analyzed. It is shown that this additional voltage is mainly due to Nernst-Ettingshausen thermo-magnetic effect. Some experimental results in 8-mm waveband are presented. This structure may serve as a frequency-selective primary transducer for detection and measurement of microwave (or millimeter-wave) power.
A new simple method for measuring complex permittivity of substantially lossy composite materials is presented. In this method, a sample of the material under study should completely fill in the cross-section of the single-mode transmission line (waveguide), and the length of the sample must be an integer of a half-wavelength in the waveguide filled with this material. The oscillator frequency is swept linearly, the minima of the reflection coefficient are measured, and then analytical formulas are used to calculate real and imaginary parts of permittivity. The method was tested on magnetodielectric samples containing hexagonal ferrite powders, as well on such dielectric materials, as PMMA, schungite composites, and alabaster. This method can be a useful technique for measuring dielectric properties of absorbing materials designed, for example, for electromagnetic shielding purposes.
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