Phase IV (United States)

Modeling of complex hardware/software systems is becoming more difficult due to the complexity of interactions that occur between hardware and software and the need to model each component at multiple levels of detail. System modeling languages such as SystemC are assisting in this area by allowing real application level software to be interfaced with hardware models that maintain great fidelity to the actual hardware realization. This paper describes a project to develop a model of a large complex hardware/software system that is the heart of a parallel processor interconnection architecture being developed at The University of Alabama in Huntsville. The model developed allows the investigators to vary the parameters of system workload, policy for message passing protocols, and hardware features such as size of elasticity buffers and DMA controller burst size in a single homogeneous model. Initial results are encouraging and the hope is that as SystemC synthesis tools become available, the hardware components of the model can be translated automatically into hardware designs for FPGA and other rapid prototyping platforms without redesign or coding.

Modified radiation pattern and gain expressions are presented for small aperture horn antennas. The E-plane pattern is identical to that provided by the classical Stratton-Chu formula, while the H-plane pattern is a modification of the Stratton-Chu formula accounting for fringe currents radiating from the edge of the aperture. An empirical approach is taken to determine the coefficient applied to the radiating currents. Comparison with measurements indicates that it is possible to predict the half-power beamwidths within a degree and gain to within a fraction of a dB.

A terrestrial based 4.8-meter dish is presented. The dish is constructed using lightweight, thin film technologies used in spaced-based platforms. Seaming two parabolic dish films together forms a lenticular. One film is coated with a silver flake conductive paint, and the other is RF transparent. The lenticular is inflated to hold the parabolic shape of the dish. The lenticular is attached to the inside of an inflatable spherical radome. The radome provides environmental protection to the thin film lenticular. The lenticular and radome are designed such that the focal point is located on the surface of the radome. An RF feed is attached to the radome at the focal point. The gain of the dish is measured using the sun as an RF source. Solar gain measurement data is presented showing the measured peak gain from the sun and the width of the main beam.

The architecture and design of a Modular Distributed Avionics System (MDAS) for launch vehicles are presented which attempt to lower costs in several ways: use of commercial components and processes; common module design which includes flexible sensor signal conditioning and flexible valve control; reduction of cabling cost and weight; elimination of power conditioning requirements; reduction of battery requirements; use of ISO 11898 CAN serial command and data bus; total programmability via umbilical; standard software with all commands and functions that are customized to a specific timeline via an overlay of a high-level of the operational sequence and timeline.