December 2001

The VectaStar Outdoor Unit consists of a sealed, cast aluminum enclosure that houses all the electronics necessary to transmit and receive broadband data via the Fixed Wireless Access (FWA) solution. The enclosure is further cased in a plastic cover that acts as a sun shield and a Radome (protection for the antenna). Sited on exposed buildings, the VectaStar Outdoor Unit must be ultra reliable, maintenance free and aesthetically pleasing. The Unit must dissipate around 50 watts, without the use of fans, in climatic conditions ranging from -50篊 to +60篊, including solar loading. The aluminum enclosure provides the Unit's heat sink. The original design brief had highlighted heat transfer issues and it was clear that the plastic cover must allow enough air to flow over the heat sink fins to cool the electronics. Using Flotherm Computational Fluid Dynamics software, TDS and Cambridge Broadband optimized the enclosure design to maximize airflow and heat transfer. The analysis included alternative heat sink configurations and worst case mounting angles.
Results of the thermal analysis gave a good correlation with early practical tests, giving Cambridge Broadband added confidence in the TDS results. With the design nearing completion, Flomerics' TDS engineers were able to create very quickly an accurate model representation of the VectaStar Outdoor Unit using the solid form CAD files. The model included the internal placement of all the critical components and the initial casting's heat sink configuration. Through detailed discussions this model was then optimized to achieve a closer correlation to the true internals of the Unit. The Flotherm model allowed the Cambridge Broadband design engineers to try many different configurations that would have been virtually impossible to replicate with physical testing within a reasonable time period.

Commenting on the TDS analysis, David Rippington, Mechanical Design Engineer, Cambridge Broadband, said, "Working with TDS was definitely beneficial to the project. The TDS analysis confirmed the thermal integrity of our original VectaStar design and guided us in making modifications that optimized the Unit's heat transfer rate. The Flotherm model allowed us to try things that would have been extremely time consuming and expensive with practical testing."

Mike Lees, Director of Manufacturing at Cambridge Broadband, added, "We were very pleased with the results of the TDS analysis. We confirmed that the VectaStar meets its stringent environmental specifications and this gave us the confidence to press ahead with the major expense of tooling for production."