Background. Contents of this release note:

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1 Contents of this release note: Background Change for tabulated rims in GRASP Change of PO grid density control for advanced grid in GRASP Change of PO grid density control for tabulated_mesh in GRASP Bug fixes in GRASP9 related to tabulated rims Other bug fixes in GRASP9 Commands for generating opengl- and xyz-plots marked as obsolete Known problems in GRASP9 Background In GRASP a new advanced PO integration grid was introduced. The primary purpose was to enable the PO analysis of reflectors with a central hole and either rectangular or triangular rims using a single get_currents command, which was not possible previously (the user had to manually subtract the PO contribution from the central hole by issuing a second get_currents command). In GRASP a new feature for analysing reflectors with arbitrary holes was added. The new advanced PO grid was used to enable this analysis. Moreover, the PO calculation scheme for analyzing reflectors featuring tabulated rims with either linear interpolation or corner points was changed in GRASP from using the standard rho-phi grid to the new advanced grid. The purpose of this change was to avoid the problems associated with the fact that the rho-phi integration grid is slowly convergent when the rim is non-differential. Hence, in GRASP the advanced PO integration grid is used for PO analysis of: Reflectors with a central hole and either rectangular or triangular rim (new feature introduced in GRASP9.7.01), Reflectors with arbitrary holes (new feature introduced in GRASP9.8.01), Reflectors featuring tabulated rims with either linear interpolation or corner points (calculation scheme changed in GRASP for the purpose of increasing integration convergence).

2 Change for tabulated rims in GRASP Several GRASP customers have experienced cases for which the PO analysis of reflectors with tabulated rims is more time consuming after the rho-phi PO integration grid has been replaced by the advanced grid. This happens, for instance, when tabulated surfaces are involved. To avoid this problem, GRASP will again use the standard PO rho-phi integration grid for all types of tabulated rims, except when arbitrary holes are present. In conclusion, for PO analysis the advanced integration grid will be used in GRASP when considering Reflectors with a central hole and either rectangular or triangular rims, Reflectors with arbitrary holes. Change of PO grid density control for the advanced grid in GRASP The advanced PO integration grid was originally constructed such that its density was determined entirely by PO1, and PO2=0. In GRASP the advanced grid is constructed differently so that the density is determined by both PO1 and PO2 and consequently, PO2 no longer equals zero. This change will speed up the PO autoconvergence. PO-autoconvergence should always be used to determine PO1 and PO2, since no rule-of-thumb exists for these values. Change of PO grid density control for tabulated_mesh in GRASP In GRASP the PO integration grid for a tabulated_mesh is changed so that the grid density is determined by both PO1 and PO2. Previously, the grid density was determined only by PO1, and PO2=1. This change will speed up the PO autoconvergence. PO-autoconvergence should always be used to determine PO1 and PO2, since no rule-of-thumb exists for these values. Scattering analyses by MoM are unaffected by this change. 2

3 Bug fixes in GRASP9 related to tabulated rims Base package (all users): 2262 Advanced PO integration grid generation can be very time consuming The generation of the advanced PO integration grid can be very time consuming if the reflector surface cannot be accurately represented by the mesh. This happens, for instance, for the surface Irregular xy-grid, Triangulation with linear interpolation Error when analyzing reflectors with tabulated rims In some cases, a PO analysis of a reflector having a tabulated rim with linear interpolation results in the error message "Cannot calculate length of rim on reflector" Segmentation fault in rare cases for reflector with holes Segmentation fault occurs in rare cases when using a tabulated rim to specify a hole in a reflector. MoM add-on only: 2261 Wrong MoM mesh of reflectors with tabulated rims A MoM mesh of a reflector with tabulated rim and with linear interpolation and no corner points can result in a mesh containing curved rims MoM mesh generation fails When scatterers to be meshed have boundaries on or close to one of the coordinate axes of the scatterer, the error "mesh outside bounding box" may be issued MoM mesh for tabulated rims with linear interpolation uses too much memory The generation of a MoM mesh for reflectors having tabulated rims with linear interpolation or corner points can take up several GB of memory. 3

4 Other bug fixes in GRASP9 Base package (all users): 2264 XY-lines plot fails For certain settings of the attributes x_lines and y_lines in the reflector_plot object, the xy-lines plot for reflector with holes goes into an infinite loop Crash when setting coor_sys_attribute in po_multi_face_scatterer GRASP may crash if the coor_sys_attribute in a po_multi_face_scatterer object is set. MoM add-on only: 2239 Exclude_faces attribute missing from box object In previous versions of GRASP the exclude_faces attribute can be used to exclude faces of the box in MoM calculation. This feature is missing MoM calculation crashes in rare cases for meshes containing small triangles The MoM computation could crash if ALL the following conditions are met: 1. The mesh contains at least one triangle 2. The triangle has an external edge, i.e., an edge not connected to other patches 3. The triangle has two internal edges, i.e, it is not located at a corner. 4. The external edge of the triangle is shorter than a quarter wavelength at the highest frequency. 5. The default polynomial precision of zero is used. Depending on the orientation of the triangle GRASP could then crash in one out of three cases. The error is not triggered if the polynomial precision is increased to one or higher as a part of a standard convergence check. 4

5 QUAST add-on only: 2336 PO on rooftop mirror gives wrong results The PO field computation is in error for rooftop mirrors. This error applies only to GRASP Problem with frames Connection of frames does not work. Coupling add-on only: 2296 Rename of coordinate system does not always work for movement_definition If the coor_sys_for_movements and moved_coordinate_systems attributes in a movement_definition object refer to the same coordinate system, and the user attempts to rename this coordinate system, GRASP crashes. Commands for generating opengl- and xyz-plots marked as obsolete The following commands for generating xyz- and opengl-plots: get_xyz_plot add_xyz_plot get_all_xyz_plot get_ogl_plot add_ogl_plot get_all_ogl_plot are marked as obsolete in the reference manual, and will therefore be removed in a future version. 5

6 Known problems in GRASP9 Ticket Bug description (Windows Vista platform only:) Warning during installation of dongle drivers on Windows Vista When GRASP9 is installed on a node-locked license with a USB dongle, Windows Vista may report a potential problem during the final steps of the GRASP9 installation. The warning message is This program might not have installed correctly which should simply be ignored by clicking Program installed correctly. (Windows Vista and Windows 7 platforms only:) Missing help viewer The GRASP GUI uses a 16-bit help viewer which Microsoft is no longer distributing with Windows. When access to the online help is attempted, the user can follow on-screen instructions and download the missing component from Microsoft. TICRA Communications systems and antennas Læderstræde 34 DK-1201 Copenhagen K Denmark ticra@ticra.com 6