ALBERT

Description: Accurate computer modeling of passive circular waveguide components is often required during the design phase for optimizing frequency response and/or determining the tolerance required on components in order to meet radio frequency specifications. Many circular waveguide devices can be represented either exactly or approximately as a series of circular waveguide sections which have a common center. In addition, smooth tapers and horns of arbitrary profile may be approximated by a series of small steps. The Scattering Matrix Program for Circular Waveguide Junctions, CWGSCAT, computes the scattering matrix for a series of circular waveguide sections. These sections must possess the same center, but the radius and length of each section is completely arbitrary. Devices that may be analyzed include a simple waveguide step discontinuity, such as that used in a dual mode horn, a stepped matching section, or a corrugated waveguide section with constant varying slot depth. Certain types of corrugated horns may also be analyzed with this program. The model used will accurately predict the reflection and transmission characteristics of such devices, taking into account higher order mode excitation if it occurs as well as multiple reflections and stored energy at each discontinuity. For large devices, with respect to a wavelength where many modes may propagate, the reflection and transmission properties may be required for a higher order mode or series of modes exciting the device. Such interactions are represented best by defining a scattering matrix for the device. The matrix can be determined by using mode matching at each discontinuity present. The results for individual discontinuities are then cascaded to get the matrix for the entire device. CWGSCAT is written in FORTRAN to run on IBM PC series computers and compatibles running MS-DOS. It requires 355K of RAM. The standard distribution medium is a 5.25 inch 360K MS-DOS format diskette. CWGSCAT was developed in 1987, and this version was released in 1991. This program is a copyrighted work with all copyright vested in NASA. IBM is a registered trademark of International Business Machines. MS-DOS is a registered trademark of Microsoft Corporation.