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The key objective was to develop a single Ka-band transmit module for Digital Video Broadcast Return Channel by Satellite (DVB-RCS) with two MMICs comprising a solid state power amplifier and a combined mixer/driver chip. The approach was driven by the need to minimise cost in volume manufacture, through optimisation of the manufacturing process, circuit design, packaging and module build.
The main benefit was to achieve a low cost return channel for DVB satellite applications that allows increased, two-way connectivity particularly in rural and remote areas of the world, where landline and mobile infrastructure are not available. Such a system is expected to provide internet access to individuals, businesses and communities at a reasonable cost.
Figure 1: Block diagram of the DVB-RCS upconverter
Key requirements included the development of a suitable 6” GaAs photolithographic stepper-based process to deliver the necessary power at 30GHz and the design of a no-tune waveguide filter capable of achieving a very demanding rejection characteristic. The proposed solution was initially based on a generic specification outline provided by the SatLabs group. In order to achieve this, Filtronic drew from its expertise in MMIC design and fabrication and benefited from its core competence in the development and manufacture of microwave transceiver modules and filters. The key to project success was the close collaboration of the technical groups within Filtronic, utilising their respective areas of expertise.
Figure 2: DVB-RCS upconverter including mixer, filter and SSPA (coaxial connectors and DC pins for demonstration purposes only)
Initially, the project focused on active and passive MMIC elements, along with the formation of the foundry design kit followed by design, manufacture and characterisation. Integration was considered and the QFN package solution was adopted compatible with low-cost volume manufacture. Filter work was carried out in parallel. The final aim was to achieve module compliance when manufactured using standard low-cost, high-volume techniques. Up-converters are demonstrated suitable for integration into the DVB-RCS requirement. Modules are shown to have the desired characteristics and an exercise is carried out to identify issues which would be encountered in a low-cost manufacturing environment.
The project is now nearing completion and a total of fifty transmit modules have been fabricated using standard surface-mount production techniques and have incorporated the packaged MMICs specifically designed and manufactured with a process developed for this application.
Modules were tested for primary parameters such as output power, return loss, linearity, and unwanted signals over the specified temperature range. Reliability testing was also carried out and was shown to be compliant.
Further to successfully demonstrating the design concept with actual units, investigation into identifying the drivers for continuous yield improvements is currently underway.