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This paper presents the design, fabrication, and experimental results of a 1:4 monolithic power distribution network for K u-band array antenna applications. The network integrated on a high-resistivity silicon (HRS) substrate surface stabilized by polysilicon consists of three Wilkinson power dividers, four dc blocking filters, and four coplanar waveguide (CPW)-to-microstrip (MS) transitions. Each output ports are fed with a barium-strontium-titanate phase shifter. It is found that the introduction of the polysilicon layer between the oxide and HRS reduces RF losses significantly, which will enable the monolithic integration of high-power controller modules onto silicon because of the existence of the oxide layer, preventing any degradation of RF performances. The individual components show insertion losses ranging from 0.4 to 2.6 dB at 15 GHz, and the interconnecting CPW lines result in a loss of 0.064 dB/mm. This network was successfully integrated with MS patch antennas monolithically, showing good performance of 32-dB return loss at 14.85 GHz, and 10[degrees] beam-steering capability. Index Terms--Antenna distribution network, BaSrTi[O.sub.3], monolithic microwave integrated circuits (MMICs), phase shifter, phased-array antenna.

Optimization of the carbon fiber composite for a microwave absorber is presented. The predicted results are based on the modulus of permittivity which obeys a logarithmic law of mixtures while the dielectric loss tangents are related through a linear law of mixtures. Linear regression analysis performed on the data points provides the constants which are used to predict the effective permittivities at different frequencies. An optimization program is written to compute the optimum amount of carbon fiber paste and thickness required for each layer. As shown, the predicted results agree quite well with the measured data. Index Terms--Carbon fiber composite, free space measurement system, microwave absorber, optimization.

This paper relates for the first time, multiple resonant frequencies of fractal element antennas using Koch curves to their fractal dimension. Dipole and monopole antennas based fractal Koch curves studied so far have generally been limited to certain standard configurations of the geometry. It is possible to generalize the geometry by changing its indentation angle, to vary its fractal similarity dimension. This variation results in self-similar geometry which can be generated by a recursive algorithm. Such a variation is found to have a direct influence on the input characteristics of dipole antennas. The primary resonant frequency, the input resistance at this resonance, and the ratio of first two resonant frequencies, have all been directly related to the fractal dimension. Curve-fit expressions can also be obtained for the performance of antennas at their primary resonance, in terms of fractal iteration and fractal dimension. The antenna characteristics have been studied using extensive numerical simulations and are experimentally verified. These findings underscore the significance of fractal dimension as an important mathematical property of fractals that can be used as a design parameter for antennas. The use of these ideas would not only reduce the computational intensity of optimization approaches for design of fractal shaped antennas, but also help antenna designers approach the problem systematically. Design formulation for antennas based on other fractal geometries can be similarly obtained after identifying suitable parameters of variation. This would therefore help analytical design of multiband and multifunctional antennas using fractal geometries. Index Terms--Fractals, multifrequency antennas, wire antennas.

Polyvinylidene fluoride (PVDF), a piezoelectric material, has various applications, and models of devices would be useful to engineers. But the benefit of such models depends on the accuracy of models' material properties. The aim, here, is to measure elastic, dielectric and piezoelectric properties over a frequency range, including the imaginary part (loss) of these properties.

Design, characterization and application of bulk ferroelectric materials for phase shifting and beam steering are discussed. Variable delay lines with a maximum phase shift of 157 degrees are integrated into a conformal array, with beam scanning of plus or minus 12 degrees is achieved prior to other optimizations.

High current carrying cables used in power transmission lines create strong magnetic fields in their vicinity. For ac lines at 50-60 Hz, the magnetic field is quasi-static and hence uncoupled from the electric field. Shielding of such low frequency magnetic fields is a challenge. In this paper, finite element modeling is used to study the effect of various shield geometries and shield materials around a current carrying wire. Two-dimensional analysis is sufficient: for this problem because the cables are very long compared to the wire diameters. Shielding effectiveness, defined as the difference in the magnetic field intensity with and without the shield, is presented. It is concluded that a partial shield is the optimal design for shielding the region below the cable. To achieve this, the shield gap must be oriented above the high current wire. Index Terms - Finite element modeling, magnetic fields, power lines, shielding.

The finite element method was used to model piezoelectric sensor fidelity. The modeling approach was applied to the sensor's structure and the fluid around the transducer. The sensor response on an immersed plate structure was quantified and the sensor's voltage was considered a function of the device and host material properties. Results reveal that structural properties affect piezoelectric sensors.

Finite element modeling is used to determine if the size and optimal placement of disk-shaped piezoelectric actuators promote active noise control. The approach led to significant noise reductions even in instances where acoustic pressure loading is changed. The approach was validated by evaluating the broadband noise reduction levels after actuators were positioned and their voltages adjusted.