Nonlinear Loss Model In Absorptive-Type Ferrite Frequency-Selective Limiters

Absorptive-type ferrite-based frequency-selective limiters (FSLs) utilize nonlinear (NL) phenomena in magnetized ferrites to provide real-time analog signal processing of RF/microwave electromagnetic (EM) signals. There are no commercially available modeling tools that simulate these interactions, and the development and optimization of FSLs are largely done experimentally. FSL modeling and design is complicated by NL, multiscale, and Multiphysics nature of operation. In this article, an NL loss model in a ferrite is proposed and implemented in an efficient numerical algorithm. The equivalent linear magnetic loss tangent is represented in a closed form. A full-wave numerical EM model with high-fidelity meshing is set up so that material properties are assigned to each mesh element and are iteratively adjusted depending on the local magnetic field. The numerical model is sliced along the EM wave propagation, and an NL eigenvalue is obtained for each slice as a function of frequency, power, and external magnetic bias field and stored in lookup tables. The slices are cascaded, and power attenuation is calculated with loss changing along the wave path according to the lookup tables. The resulting data are processed to be suitable for equivalent circuit models. Numerical results for coplanar waveguide FSL are validated by measurements. The proposed modeling approach is useful for engineering FSL devices

Studies on radar medical sensors

Ultra-wideband (UWB) radar enables detection and imaging of electrically contrast dielectric and conducting objects inside the human body that can be used to detect tumors, internal wounds and support other medical diagnosis along with mapping different metal/dielectric inclusions to navigate, e.g. a robotic surgical tool. General principles to design such systems and their building blocks are discussed along with implementation challenges. Two biomedical test radar systems are described to illustrate the study

Time-domain antenna studies for videopulse subsurface radars

The results of time-domain theoretical and experimental studies of ultra-wide band antennas with impulse excitation in radiating and receiving modes are presented. The antennas under consideration, like a monopole antenna, a dipole antenna and a horn-like antenna, are used widely for high-resolution videopulse subsurface (ground-penetrating) radars and should be operated near the border between two medias with different electrical properties

UWB radar imaging system with two-element receiving array antenna

UWB signals can propagate in cluttered environment and opaque media that enables exploring hidden homogeneities through registering and processing backscattered signals. One of such an application is UWB through-wall vision radar (UWBR), Sostanovsky (2004a), Radar Vision (2005). A prototype of low-complexity and low-cost portable UWBR sensor with a small receiving antenna array is presented. Several key implementation issues are discussed including design of antennas and other electromagnetic-related aspects of signal processing algorithms for time-domain focusing and imaging. Simulated and measured radar images demonstrate radar operation to map out a person behind walls

Physical aspects of mutual coupling in finite broadband tapered slot (Vivaldi) arrays

A notch antenna, or Vivaldi antennas, or also known as tapered slot antenna (TSA) is widely used as a single radiator but mostly as an array element in transmitting, receiving and combined arrays, focal-plane imaging and other system-oriented broadband applications. Full-wave analysis of such arrays is required that is a big numerical challenge because of large electrical size for such typical problems. Only infinite arrays or very small arrays are treatable with available EM tools. However, all elements of moderate in size arrays can be impacted by edge truncation because of strong mutual coupling within TSA array environment. Thus, accurate performance prediction and design can be achieved through (1) enhancing EM simulation numerical tools and (2) exploring underlying physical phenomenology of array behaviour. We follow both the above ways. This work demonstrates some basic physics related to mutual coupling is small finite arrays

High-power multiplexer for aerial feeder of TV and radio broadcasting transmitters

Some ways of technical implementation of a high-power multiplexer for common operation of several broadcasting transmitters in the metric and decimetric waves band are considered. These transmitters pick up and carry a common aerial feeder that allows extending a net of TV and radio broadcasting by complete using opportunities of existing equipment. Engineering solutions proposed to build high-power multiplexers have been developed, designed, manufactured, tuned, tested in laboratory and under high-power operation mode. Some of those multiplexer are used now at TV and radio broadcasting centers in Ukraine since 1994

Wave propagation and coupling in linear arrays with application to the analysis of large arrays

Waves inside linear arrays are analyzed for the case of single port excitation. A frequency-domain method is proposed for the extraction of the amplitude decay and phase velocity of the waves, based on simulation results obtained for terminal excitation at one end and near the middle of the array. The waves reflected by the array ends are also extracted, under a single-reflection assumption. This model is then exploited for estimating the port currents when other elements of the array are excited, as well as for larger arrays. Simulation results are shown for port currents and element patterns in arrays of broad-plate dipoles