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This paper describes a new low-pass filter topology based on tapered periodic structures. These filters exhibit interesting characteristics in terms of compactness, return loss, insertion loss, selectivity, and the suppression of spurious frequency bands. Hybrid prototypes with a 1-GHz cutoff frequency, based on a coplanar-waveguide technology, and using both low-cost and high-performance substrates, have been fabricated and measured. Spurious frequency bands can be suppressed to below -22 dB at frequencies up to 20 GHz. Passband ripples are negligible, and the return loss is better than 20 dB. A two-section filter has a length of 0.2 [lambda] and exhibits a--120-dB/dec selectivity, while a six-section filter is 0.51 [lambda] long and has a -560-dB/dec selectivity. A design procedure has been established. These filters are compatible with monolithic microwave integrated circuit technologies in which the capacitors can be realized as metal-insulator-metal structures. Index Terms--Bragg cutoff frequency, low-pass filters, periodic structures, spurious frequency suppression, tapered structures.

This paper deals with a microwave microstrip line that is terminated by a laser illumination, which alters the behavior of this microwave device. The first result is the numerical simulation of the microstrip line ended by a photoinduced load with the finite element method (FEM) and with hexahedral edge elements. The main difficulties of this kind of simulation remains in the fact that we deal with an open structure and that the photoinduced load is complex and inhomogeneous. Index Terms--Anisotropic and inhomogeneous complex medium, finite element method, optical control, photoinduced load.

ABSTRACT The design of matching networks is generally based on lossless devices, hence rendering difficult to anticipate their performance when both impedances are complex. To be more predictive in terms of insertion loss and matching impedance coverage, a rigorous method is proposed for the first time to calculate the efficiency of a tunable matching network based on the quality factor of its components, with source and load complex impedances. The method allows optimizing the topology of the matching network, depending on the location of the source and loading impedances in the Smith chart. It is the first time to our knowledge that a complete analytical formulas is given to predict the matching network's efficiency in function of available components quality factors in the case of source and load complex impedance. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1160-1166, 2014 [ABSTRACT FROM AUTHOR]

In this paper, a miniaturized bandpass filter for ultra-wide-band applications is proposed. It is based on the embedding of high-pass structures in a low-pass filter. A semi-lumped technology combining surface-mounted capacitors and transmission lines has been used. The filter design rules have been carried out. Furthermore, two filters having a 3-dB fractional bandwidth of 142 and 150%, centered at 0.77 and 1 GHz, respectively, have been realized for a proof of concept. Measured characteristics, in good agreement with simulations, show attractive properties of return loss (|S11| <−18 dB), insertion loss (<0.3 dB), and a maximum group delay and group delay variation of 2 and 1.3 ns, respectively. A distributed filter based on the same low-pass/high-pass approach has been also realized and measured for comparison. The size reduction reaches 85% for the semi-lumped filter, and its selectivity is improved with a shape factor of 1.3:1 instead of 1.5:1. The semi-lumped filter's drawback is related to a smaller rejection bandwidth compared to the distributed one. To improve the high-frequency stopband, an original technique for spurious responses suppression based on capacitively loaded stubs has been proposed. Even if the performances do not reach that obtained for the distributed approach, with this technique spurious responses are pushed until eight times the center frequency. A sensitivity study vs. critical parameters has also been carried out, showing the robustness of the design. [ABSTRACT FROM PUBLISHER]

To be faster and more precise than the numerical technique for the computation of the photo-induced plasma in semiconductor, an analytical solution has to be developed. In this article, the Hankel transform is used to simplify the solution of the differential equation of second order with nonsconstant coefficient, known as the diffusion equations. The resulting expression of the 3D carrier density includes all the physical parameters of the substrate and the laser beam as well. A parametric study was also feasible using the developed expressions. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1718–1721, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21754 [ABSTRACT FROM AUTHOR]