PROFUSION Code

Collection of programs for the propagation of microwaves in waveguides and in free-space

Zig-zag propagation of a Gaussian beam in a square corrugated waveguide, which can use used as a remote-steering antenna for future fusion experiments.

The PROFUSION code (PROgrams For m Ultimode Simulation, analys Is and OptimizatioN) is a collection of programs for the propagation of microwaves in waveguides and in free-space.

Supported waveguide types are

  • Cylindrical with smooth wall
  • Cylindrical with corrugated wall
  • Rectangular with smooth wall
  • Square with corrugated wall

The code can calculate wave propagation of multi-mode spectra and mode conversion due to geometry variations (curvature, diameter change). This allows a large number of devices (bends, horn antennas, mode converters) to be simulated. The total field is a superposition of fields of the known waveguide modes in the system. This reduces the Description of a field in the waveguide cross section from a 2D-distributions to a complex 1D vector of mode amplitudes. The calculation is many times faster than full-wave simulations, but limited to geometries, where Eigenmodes are known analytically.

Field distribution in a curved rectangular waveguide with constant and optimized curvature.
Field of a gap in a waveguide with a complicated field distribution calculated with a combination of waveguide- and free space transmission.

A generic Optimization module is included to optimize gerometries of bends, horn antennas and mode converters. It starts with a simple shape and changes the geometry to get as close as possible to the desired parameters. For mode converters the optimization goal is the conversion efficiency. For horn antennas it is the (typically Gaussian) aperture field distribution. For waveguide bends it is the mode purity at the output and the maximum level of spurious modes inside the bend.

All optimizations can also be done for multiple frequencies simultaneously, which allows the design of broadband microwave components and multi-frequency ECRH facilities.

 

Free space fields are handled as complex 2D distributions. The propagation is calculated using an FFT method (plane wave decomposition). The transition from free-space to waveguides and vice versa is supported, which allows the complete simulation of transmission lines, which contain waveguides and quasi-optical elements. Furthermore there are modules for:

  • Generation of field patterns from Gauss-Laguerre modes, waveguide apertures and measured data
  • Applying focusing mirrors
  • Calculation of the beam truncation losses due to finite mirror sizes
  • Phase reconstruction of field patterns obtained by thermographic measurements
  • Analysis of field patterns obtained with a vector network analyser and a 2D scanner

   

Dr.-Ing.

Burkhard Plaum

IT and Research associate, Microwave Technology

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