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QW-Simulator - unique, conformal FDTD solver. Its output data include multi-modal, multi-port S-matrices, radiation and scattering patterns, pattern of field, dissipated power, time-domain reflectometry etc.
QW-Simulator utilises state-of-the-art FDTD algorithms as well as many original models and procedures developed by the authors of the program during nearly two decades of intensive research on the time-domain electromagnetic modelling. The following features should be emphasised:
General view of QW-Simulator
accurate and stable conformal representation of curved metal boundaries
higher-order modelling of media interfaces
wide-band modelling of skin effect in lossy metals
guaranteed spurious-free behaviour of the algorithm, also in the presence of strong spatial irregularities
matched modal excitation based on the field and impedance template, with user-controlled available power and various waveforms
lumped ports with user controlled available power or injected current
a new system of S-parameter extraction incorporating differential decomposition of fields into incident and reflected waves, template filtering for desired mode extraction, compensation for imperfect absorbing boundaries
extraction of S-parameters between transmission line ports, which support propagating and/or evanescent modes, and lumped ports
a variable source impedance technique for emulation of pure eigenmodes in inhomogeneous resonators
anisotropic boundary conditions (wire grids)
QW-Simulator permits to store calculated fields and results on the disk. The available options include:
QW-Simulator also offers many ways of visualisation of simulated fields and calculated circuit characteristics, including:
hilltop and thermal display of instantaneous field values in any plane perpendicular to any of the coordinate axes
hilltop and thermal display of two-dimensional field envelopes in any plane perpendicular to any of the coordinate axes
hilltop and thermal display of SAR and dissipative power - instantaneous, maximum, and average values
field envelopes along any line parallel to one of the coordinate axes, with a possibility of virtual measurements of attenuation and SWR
field variation in time at any point, for TDR applications in particular, with possibility of virtual measurements of reflection coefficient and location of the discontinuity
S-parameters versus frequency in linear, quadratic or logarithmic scale, on Smith chart and in polar coordinates,
·radiation patterns versus angle accompanied by antenna efficiency, radiation resistance, and radiated power for a set of frequencies
maximum, minimum, and average values of power dissipated in electric and/or magnetic field, and energy stored in electric and/or magnetic field, in the whole circuit or its selected subregions, and the resultant Q-factors
exporting S-parameters in Super Compact and Touchstone formats
saving S-parameters, eigenvalue charts, and antenna characteristics in text files of either QW or pure data formats
dumping instantaneous field values of all field components, in the whole circuit, in text files
dumping 2D envelopes of selected field components and in selected layers in text files
dumping 1D envelopes of selected field components along a selected line in text files
Watching simulation results
QW-Simulator allows watching how the frequency and angle dependent characteristics of the analysed structure are being calculated:
In the case of Antenna characteristic 2D, an additional Radiation Patterns dialogue will first come up, prompting the user to define constant angle, variable angle step, reference axis, reference point for phase extraction, and the method of reference power integration.
In the case of Antenna characeristic 3D, the 3D Radiation Patterns dialogue appears, prompting the user to define step in angles Phi and Theta, reference axis and a single frequency at which the pattern will be produced.
FD-Probing and FD-Pavailable results
Antenna Fixed Angle results
Antenna characteristics 2D
For periodic structures, nulls at all of the feasible diffraction orders are indicated with the vertical dashed lines.
To see a periodic example, click here.
Antenna characteristics 3D
QW-Simulator allows dynamic monitoring of field distributions during time-domain simulations with any kind of excitation. For such monitoring no special arrangements are needed before launching the simulation. The user can decide at any time of the simulation: which fields are of interest, what kind of displays he prefers and how many windows he wants to open.
Monitoring time-depended fields
View Fields in V2D and COAX circuits now shown in 3 planes (two x-rho planes at selected angles within a structure and one rho-phi plane).
To see an example, click here.
Displaying frequency-domain field magnitudes
Time domain displays are very useful and flexible but they are most informative with a sinusoidal excitation at a particular frequency. Thus one frequency can be thoroughly investigated at a time. QW software allows also watching the field distributions at selected frequencies from data extracted by Fourier transforming of the results of simulation obtained with pulse excitation. Such a postprocessing is called FD-Monitoring.
Watching electromagnetic quantities along a line in space and versus time
Testing FDTD mesh
Power, energy and Q factor
Test Mesh window allow to see layer by layer how the FDTD grid has been created by the QW-Editor. For a cell pointed by a cursor, its position, cell type and filling media are shown in window status. This is an important tool of verification if the mesh used in QW-Simulator corresponds to the intentions of the user. User's errors in application of the QW-Editor will be visible here. For example, it is a typical error that the user assigns to a particular element the medium outside instead of inside or vice versa. Such a setting may be in conflict with settings in other elements, producing rather unexpected results, which will be easy to detect using the Test-Mesh option.
Test Mesh window is also very useful in verification of the parameters of the media. The user may want to verify if the media properties transferred to QW-Simulator are those he intended to assume. In Test Mesh window please point the cursor to the FDTD cell of interest and invoke Setup - Media Info. In the Medium Info window the complete information about the medium is displayed.
The question of verification of the assumed media properties becomes even more important in the case of dispersive media. In QW-Editor we introduce dispersive properties of materials by choosing appropriate model (e.g. Debye, Drude, Lorentz) and specifying a few parameters. Such a system may be prone to human errors and the user may want to verify if the frequency-dependent properties of the medium in the frequency band of interest are such as he required. This can be done by invoking Dispersive Media Info to obtain an image where the media parameters are displayed in the frequency band of interest (the band specified in the project's Postprocessing range). Note that the window used to display the dispersive medium parameters is essentially the View Results window and thus a variety of options including scaling, mathematical operations on curves etc. is also possible here.
Test Mesh window is also useful in verification of the position and parameters of Lumped impedances inserted into the FDTD grid. After choosing the proper level and pointing to the proper FDTD cell we can display the properties of the Lumped impedance.
The field distribution along a particular line parallel to one of the coordinate axes. For example, if X-axis is selected, we further specify Y-coordinate and Z-coordinate of the line. These coordinates should be introduced in FDTD cells, but their absolute position (in millimetres) will be displayed in the right bottom part of the View Envelope window when Markers in on.
The field distribution versus time shows variation of the selected component in time at a particular point of the circuit. We must specify X-coordinate, Y-coordinate and Z-coordinate of the point and how many time samples will be displayed in the window and can be saved in the file.
Click here to see a time domain reflectometry example.
Upon the View-Power&Q command, the QW-Simulator starts searching for time-maximum and time-minimum values of power dissipated and energy stored in the circuit. Initially, it sets the maximum and minimum values of all quantities to zero. Then at each time-step it integrates (over the whole circuit) power and energy, re-calculates their maxima and minima, and presents the results in the Power, Energy & Q-Factor window.
Click here to see S-parameters extraction examples.
Freeze of state
Using freeze menu command and freeze tasker command user can save state of the QW- Simulator in the purpose to restore this state, view results for this state or continue calculations in the future. All QW- Simulator functions work in the same normal manner after defreeze operation. This is very convenient feature in many situations. Below there are typical scenarios:
user wants to replace calculations from one computer to another
user wants to save time consuming calculations
user wants to present stable state of calculations for particular large project very quickly
Note that for large projects user has to take into account amount of also large hard disk space used during freeze operation, which is approximately equal of the project RAM memory requirements.
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