Physical Optics (PO)

Applicability of method

The EfieldFD PO solver is suitable for analysis of very large problems where the electrical size of the problem is to large for MLFMM. Typical applications include

  • Radar cross section (RCS) analysis
  • Antenna integration on large structures
Surface currents of UAV computed with PO
Figure 1:  Surface currents of UAV computed with PO

Description of method

PO is a high frequency approximation (short-wavelength approximation) that is an intermediate method between geometric optics, which ignores wave effects, and full wave methods such as MoM or MLFMM. The geometrical optics current is used over the illuminated portions of the target surface, while zero current is assumed over the shadowed portions. The current is then used in the radiation integrals to compute the scattered far field from the target. PO gives best results for electrically large bodies and is most accurate in the specular directions.

Solver features

The EfieldFD PO solver is based on a triangular surface mesh such as MoM or MLFMM but also on a NURBS geometry representation. The NURBS is used to determine which parts that are illuminated or not. Approximate shadow regions are obtained efficiently on the NURBS surfaces using raytracing techniques. Practically, a test on the outward normal at each triangle is combined with an occlusion test using ray tracing on NURBS.

Material and Boundary conditions

The EfieldFD standalone PO solver is mainly used to compute RCS so perfect electric conductors (PEC) can be modeled.

Excitations

Available excitations in the EfieldFD PO solver are plane wave excitations

Post-processing

Output from the EfieldFD PO solver includes:

  • Far-fields (2D, 3D, directivity, gain, field pattern and polarisation)
  • Radar Cross section (RCS) calculation, bistatic and monostatic
  • Near-fields
  • Surface currents
  • Far field power
  • Power through user defined surfaces

Parallelization and out-of-core

The EfieldFD PO solver is parallelized for both shared memory and distributed memory computers. The solvers can be run either in out-of-core mode or in in-core mode depending on available memory.