A modified dynamic model for planar microwave circuits

Substrate-integrated waveguide (SIW) technology has recently drawn attention to its benefits in the microwave field, such as integration in planar microwave circuits, low manufacturing cost, and high-quality factor compared to other technologies. In this paper, a broadband and high gain SIW cavity-backed L-shaped slot antenna structure has been designed and made for X-band applications. Three pairs of L-shaped half-wave resonators are placed on the lower wall of the cavity (backed-slots) to further expand bandwidth and improve gain. The final antenna designed operates on a band ranging from 9.4 to 10.5 GHz with a bandwidth of 11%. Moreover, the gain reaches a value of 9.5 dBi. The final antenna is realized on a Rogers RT/Duroid 5870 substrate. The gain, the reflection coefficient, and the radiation patterns are measured and compared to the EM simulation results and a very good agreement is obtained. The proposed cavity-backed L-shaped slot antenna gives a good compromise between a high gain and a large bandwidth.

An efficient method to improve the integral equations method is presented in this article. A delta gap source generator and the fundamental mode sampling technique are employed. By employing this modified method, observation of the SWR and the creation of a large matrix in the conventional method employing a delta gap source generator are not necessary. Also, the modeling complexity and the time-consuming computation of the conventional method, which employs the semiinfinite traveling-wave mode, are avoided. In this article we use the coplanar waveguide short-end discontinuity as an example to describe this method in the spectral domain. Moreover, numerical results are compared with our experimental data and they show good agreement. ©1996 John Wiley & Sons, Inc.

This work presents performances of a tunable microwave straight edge resonator (SER) on a silicon membrane. The aim of this approach is to obtain a miniaturised MSW device, integrable in a planar microwave circuit. S/sub 11/ and S/sub 21/ parameters of this device are presented for various magnetic polarizing fields showing frequency tunability between approximately 4.2 GHz and 7.25 GHz. Using silicon membranes to support these devices offers important openings toward SER integration in MMIC.

Planar microwave circuits are simulated by a mixed space-spectral domain integral method which allows the consideration of space-varying impedances. For an efficient computation of scattering parameters of circuits containing lumped elements within this fullwave analysis, a bilinear transformation is used. Furthermore, by this so-called Mobius transformation it is possible to decide whether an impedance region of finite size can be interpreted as a lumped element or not. Applications to microstrip circuits are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper presents the results of an investigation of leaky wave antennas designed on a substrate integrated waveguide. The antennas are of the following types: antenna radiating from a slot in the top waveguide wall, CRLH and dual band CRLH leaky wave antennas. The substrate integrated waveguide can easily be integrated with planar microwave circuits. Antennas designed on this transmission line have a planar structure, and can be fabricated by a standard PCB technology, so they are suitable for mass production.

A novel algorithm based on generalized transmission line equations (GTL) and on the method of lines (MoL) for the analysis of planar waveguide circuits with anisotropic layers is proposed and substantiated. The algorithm uses discretization lines in the propagation direction of the waves. As in the case of multiconductor transmission lines two modal matrices are determined. Impedance/admittance transformation equations are determined on the basis of the GTL equations. Using these equations numerically stable and accurate impedance transformations and field calculations can be performed.

The estimation of hydrodynamic coefficients of an autonomous underwater vehicle by comparing a dynamic mesh model with a horizontal planar motion mechanism experiment

Although hydrogen is a clean and renewable fuel, there is still a need to understand and evaluate the potential risks posed in the event of an accidental explosion. This paper presents large eddy simulation (LES) numerical analysis for lean hydrogen premixed flames propagating inside a small laboratory combustion chamber with built in solid obstructions. The small-scale chamber is 0.625 litres in volume with three removable turbulence generating baffles and a square solid obstacle. A lean equivalence ratio of 0.7 is selected in this study. The LES model is utilised to investigate the influence of obstruction configuration and area blockage ratio on the flame characteristics and the generated combustion over-pressure. The LES turbulence technique is used with an in-house computational fluid dynamics (CFD) model for compressible flows. The numerical simulations are carried out with various arrangements of the baffle plates and a solid obstacle to examine the effects of the area blockage ratio and generated turbulence on the flame structure and generated over-pressure. Two different area blockage ratios of 0.24 and 0.5 are studied. Four configurations with different baffle arrangements are studied to examine the resulting turbulence effects on the generated over-pressure, flame position-time traces and flame transient speed following ignition. Direct comparisons are made between the different baffle/flow configurations to identify the various effects of an increased area blockage ratio. Numerical results showing the flame structure at various time windows after ignition are presented and compared with published experimental images. High speed laser induced fluorescence (LIF-OH) images of the reaction zones obtained from the experiments at a rate of 5 kHz provide the flame position data and convey the impact of the turbulence generated by the baffles and solid obstacle on the propagating flame structure [1]. The pressure is recorded at a rate of 25 kHz using a piezo-electric pressure transducer in the base plate of the chamber [2]. The rise in over-pressure as a result of increased turbulence due to additional baffles and an increased area blockage ratio is found to be consistent with experimental data. This is also found to be consistent for the flame position-time and speed-time traces across all configurations. Main points of interest such as the peak over-pressure, maximum rate of pressure rise and the flame propagation trends are also observed along with variations in flame speed as the flame interacts with the baffles and obstacles. Validation of the numerical results against available published experimental data conveys good agreement confirming the ability of the numerical model to predict numerical results for an increased area blockage ratio. Further numerical simulations are also carried out for flame/flow parameters where experimental data is unavailable due to physical limitations. Satisfactory agreement between numerical results and experimental data endorses further predictions for computational models in studying vented hydrogen explosions where there is an increased risk or limited experimental data.

In this work, we propose a novel design of a planar CPW lowpass “LPF” filter based on the use of periodic structures. The periodic cells are formed from a rectangular slot repeated periodically. The originality of this work is to develop a new LPF structure which is simple, low cost for fabrication and easy to associate with others microwave planar circuits. The proposed and validated LPF is a compact planar filter structure. The final circuit is simulated and optimized by using two electromagnetic solvers, ADS (Advanced Design System) and HFSS (High Frequency Structural Simulator). After many series of optimization we have validated the final circuit into simulation by using optimization methods integrated into the both solvers, taking into account a high density of meshing in order to cover the whole circuit. The fabricated LPF circuit shows good agreement between simulation and measurement results in term of matching input impedance and insertion loss with a cutoff frequency of 1.25GHz. The entire area of the proposed LPF is 35x31 mm&lt;sup&gt;2&lt;/sup&gt;.

Experimental and numerical study on water mist suppression system on room fire

In the present work, the modeling of high frequencies planar circuits is proposed with an original iterative method based on the concept of waves. It consists in the development of simulation software based on an iterative method. The iterative method is developed from the fast modal transform on a two-dimensional fast Fourier transform algorithm. The method has been applied to the characterization and the modeling of patch antennas with notches in microstrip and coplanar technology and the quarter wavelength directive coupler. The obtained results are very satisfactory particularly in the reduction of the simulation time and the precision of the results in comparison with the literature.

Numerical cavitation noise prediction of a benchmark research vessel propeller

A new high-order-mode analytical method is described for calculating the frequency-dependent complex permittivity of a low-loss dielectric in a parallel-plate structure using a planar microwave circuit model. An analytical expression for the complex permittivity is derived in terms of the terminal impedance at a modal resonant frequency of the structure. The derivation provides physical and mathematical insight into the relation between complex permittivity and port impedance. The technique is validated by good agreement between manufacturer's specifications and complex permittivity calculated from measurements near resonant frequencies for a printed circuit board (PCB).

In this paper, we introduce a new periodic structure for CPW of a low pass filter based on the DGS technique with triangle slot cell forme. The proposed structure is a minuature low pass filter that exhibits low insertion loss in the passband, simple fabrication, and easy to integrate with microwave planar circuits.A Lowpass filter (LPF) has been designed with flat response at a selected frequency by cascading three DGS cells.

In this paper, we present a new UWB CPW low pass filter structure by using periodic elements. The originality of this work is to develop a neFigure 4 showsw UWB LPF structure which is compact, miniature, and easy for fabrication. The validated LPF is a compact planar filter easy to associate with others microwave planar circuits, having a large band pass and a large rejection band. The final circuit is simulated and optimized by using the electromagnetic solver ADS (Advanced Design System). After many series of optimizations, we have validated the final circuit into simulation by using different optimization methods taking into account a high density of meshing in order to cover the whole circuit. The simulated LPF circuit shows good results in term of matching input impedance and insertion loss with a cut-off frequency of 6.5GHz. The entire area of the proposed LPF is 16x40 mm2.