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Input Examples

A complete example for a lossless cavity

  ModelInfo: {
    File: dds3.ncdf                       //mesh file. It is the file converted using acdtool
    BoundaryCondition: {                  //specify boundary conditions. The numbers here are sideset in cubit
      Magnetic: 1, 2                      //reference surfaces 1 and 2 are symmetric planes
      Electric: 3 4                       //set reference surfaces 3 and 4 to be electric boundary condition
      Exterior: 6                         //surface group 6 (maybe many surfaces) is metal
   }
   SurfaceMaterial: {                     //for each metal (exterior) surface group, list the sigma values
      ReferenceNumber: 6
      Sigma: 5.8e7
    }
  }

  FiniteElement: {
     Order: 2                             //set the finite element basis function order to be used.
     CurvedSurfaces: on
  }

  EigenSolver: {
      NumEigenvalues:  1                  //want to compute 1 mode
      FrequencyShift: 10.e9               //the eigenfrequency of the mode should be above 10GHz
  }

Once Omega3P run is successfully completed, eignvectors are stored in subdirectory <tt>eigens</tt>. User can convert them to mode files to be visualized using paraview. The following is the command to do that:

  acdtool postprocess eigentomode eigens

A complete example about a cavity with lossy materials

 ModelInfo: {
  File: ./pillbox.ncdf
  BoundaryCondition: {
    Electric: 1,2,3,4
    Exterior: 6
  }
   Material : {
     Attribute: 1
     Epsilon:   1.0
     Mu:        1.0
   }
   Material : {
      Attribute: 2
      Epsilon:   1.0
      Mu:        1.0
      EpsilonImag: -0.2        //lossy material
   }
 }

  FiniteElement: {
   Order: 1
   Curved Surfaces: off
  }

  EigenSolver: {
    NumEigenvalues: 2
    FrequencyShift: 5e9
  }

A complete example with periodic boundary conditions

ModelInfo: {
File: c026ds-pbc.ncdf
  BoundaryCondition: {
    Magnetic: 1 2
    Periodic_M: 3   //master surface
    Periodic_S: 4   //slave surface, the mesh should be exactly same as those on the master surface
    Exterior: 6
    Theta: -150     //phase
  }
}

FiniteElement: {
  Order: 2
  CurvedSurfaces: on
}

EigenSolver: {
    NumEigenvalues:     1
    FrequencyShift: 	10e9
}

A complete example with waveguide loaded cavity

  ModelInfo: {
    File: cell1fourth.ncdf
    BoundaryCondition: {
      Magnetic: 1,2,3,4
      Exterior: 6
      Waveguide: 7             //Automatic numerical waveguide port solution will be generated per default
      //Absorbing: 7           //First-order absorbing boundary condition.  Default cutoff is 0
    }
  }

  FiniteElement: {
    Order:           1
    Curved Surfaces: on
  }

  EigenSolver: {
    NumEigenvalues: 1
    FrequencyShift: 9.e9
  }

  Port: {
    ReferenceNumber: 7
    NumberOfModes: 3              // this whole 'Port' container is only needed if you want to load more than 1 mode on a port
    //CutoffFrequency: 5.6e9      // this is only for Absorbing boundary conditions specified above.  Can be used to have the same cutoff as another waveguide mode for faster solution
  }

Analytic Ports (for polarization)

Omega3p normally uses a numerical solution for each port but if you need to specify the polarization of the waveguide you can give an analytic solution instead.

From the last example we could have used:

  Port: {
        ReferenceNumber: 7     //this number should match surface groups in waveguide boundary condition.
        Origin:     0.0, 0.0415, 0.0    //the origin of the 2D port in the 3D coordinate system
        XDirection: 1.0, 0.0,    0.0    //the x axis of the 2D port in the 3D coordinate system
        YDirection: 0.0, 0.0,   -1.0   //the y axis of the 2D port in the 3D coordinate system
        ESolver: {
                Type: Analytic              //analytic expression is used
                Mode: {
                        WaveguideType: Rectangular     //it is a rectangular waveguide
                        ModeType: TE 1 0                    //load the TE10 mode
                        A: 0.028499                            //dimension of the waveguide in x
                        B: 0.0134053                           //dimension of the waveguide in y
                 }
         }
   }

Load TEM mode in a coax waveguide

   Port: {
        ReferenceNumber: 2
        Origin:     0.0, 0.0, 0.011
        ESolver: {
                Type: Analytic
                Mode: {
                        WaveguideType: Coax
                        ModeType: TEM
                        A: 0.0011  //smaller radius
                        B: 0.0033  //larger radius
                }
        }
   }

Load TE11 mode in a circular waveguide

   Port: {
        ReferenceNumber: 2
        Origin:     0.0, 0.0, 0.1
        XDirection: 1.0,  0.0,    0.0
        YDirection: 0.0,  1.0,    0.0
        ESolver: {
                Type: Analytic
                Mode:  {
                        Waveguide type: Circular
                        Mode type: TE 1 1
                        A: 0.03
                }
        }
   }

Load two TE modes in the same rectangular waveguide

  Port: {
      Reference number: 9  // FPC
      Origin: 0.0, 0.198907, -0.4479152585
      XDirection:  -1.0, 0.0, 0.0
      YDirection: 0.0, 0.0, 1.0
      ESolver:  {
             Type: Analytic
             Mode: {
                     WaveguideType: Rectangular
                     ModeType: TE 1 1
                     A: 0.1348935946
                     B: 0.024973714999999970
            }
     }
  }

  Port: {
      Reference number: 9  // FPC
      Origin: 0.0, 0.198907, -0.4479152585
      XDirection:  -1.0, 0.0, 0.0
      YDirection: 0.0, 0.0, 1.0
      ESolver: {
             Type: Analytic
             Mode:  {
                     WaveguideType: Rectangular
                     ModeType: TE 2  0
                     A: 0.1348935946
                     B: 0.024973714999999970
            }
       }
   }
LinearSolver options in EigenSolver container
  • The first option is that user does not provide anything. The EigenSolver container in the input file looks like:
      EigenSolver: {
        NumEigenvalues: 1
        FrequencyShift: 10.e9
        Tolerance: 1.e-8
      }
    
    In this case, Omega3P will use the default option for linear solver for solving shifted linear systems
  • The second option is to use float version of the sparse direct solver.
      EigenSolver: {
        NumEigenvalues: 1
        FrequencyShift: 10.e9
        Preconditioner: MUMPSFLOAT //use the float version. memory usage reduced into half.
      }
    
  • The third option is to use Krylov subspace method with different preconditioner.
      EigenSolver: {
        NumEigenvalues: 1
        FrequencyShift: 10.e9
        Preconditioner: MP      //this use p-version of multilevel preconditioner.
      }
    
    The code will choose either CG (real matrices) or GMRES (complex matrices) and the p-version
    of multilevel precondtioner as the solver for shifted linear systems.

FAQ

How to calculate Wallloss Quality Factor?

There are two ways to do so. Each way has its advantage and disadvantage.

  1. Inside ModelInfo.BoundaryCondition define a set of boundary surfaces as Exterior.
    For each of the boundary surfaces, have a corresponding SurfaceMaterial container inside ModelInfo.
    For example:
     ModelInfo: {
      File: .dds3.ncdf
    
      BoundaryCondition: {
        Magnetic: 1, 2, 3, 4
        Exterior: 6   // sideset 6 is defined as Exterior BC.
      }
    
      SurfaceMaterial: {    // have a separate for each number in Exterior BC
        ReferenceNumber: 6  //the corresponding sideset in Exterior BC
        Sigma: 5.8e7        //electrical conductivity of the material
      }
     }
    
    After you run omega3p with the input file, you will get a file called "output" under the same directory. Inside the file, it has a summary of results such as:
                Mode : {
                    TotalEnergy : 4.4270939088102e-12
                    QualityFactor : 6478.5096350252
                    File : ./dds.l0.1.144469E+10.m0
                    PowerLoss : 4.9139118623939e-05
                    Frequency : 11444685657.626
                }
    
    
    The number after QualityFactor is the one you are looking for. This method uses perturbation theory and has advantage that it is very simple. The computation associated with it is minimal.
  2. Inside ModelInfo.BoundaryCondition, define the set of surfaces as Impedance (instead of Exterior in method 1).
    Set the HFormulation to be 1 (this is very important). Also, have a set of corresponding SurfaceMaterials inside ModelInfo as those in method 1. For example:
     ModelInfo: {
    
      File: dds3.ncdf
    
      BoundaryCondition: {
        HFormulation: 1
        Magnetic: 1, 2, 3, 4
        Impedance: 6
      }
    
      SurfaceMaterial: {
        ReferenceNumber: 6
        Sigma: 5.8e7
      }
     }
    
    After you run omega3p with the input, in the output file, you will see
            Mode = {
                TotalEnergy = { 6.2827077634198e-07, 0 },
                ExternalQ = 6579.1486638005,
                QualityFactor = inf,
                File = './dds.l0.R1.144619E+10I8.698837E+05.m0',
                PowerLoss = 0,
                Frequency = { 11446188331.641, 869883.69746227 }
            }
    
    The number after ExternalQ is the wall loss Q you are looking for. During the omega3p run, it should also print out the Q information such as
    COMMIT MODE: 0 FREQ = (11446188331.64141,869883.6974622669)	 k = (239.8943683519209,0.01823141417003215)	 Q = 6579.148663800495
    
    Note that this method set an impedance boundary condition on those surfaces and make the eigenvalue problem complex and nonlinear. It takes more time and memory to solve the problem. But the field will be in the right phase (even close to the boundary surfaces).

Both methods should give you converged Q results if mesh is dense enough.

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