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MCL designs high power RF amplifiers that serve as uplinks in
satellite communications systems. Typically, the units operate
outdoors attached to truck-mounted satellite dishes. They must be
environmentally sealed against contaminants, such as dust, rain and
snow and must handle wide temperature variations. Because the
dishes are gimbaled, the heatsinks must be as small and light as
possible.
A recent amplifier, designed for increased power, generated 1500
watts of thermal energy from the main module and 400 watts from an
accessory module. To reduce size and weight, the heatsink was
designed to form part of the sealed amplifier enclosure. Heat
conducted to ambient was dissipated by an external waterproof
fan.
Thermal performance versus weight became a real challenge during
heatsink development. Higher performance designs created over
weight conditions, while the lighter designs did not adequately cool
the components. To balance the performance versus weight,
MCL enlisted Coolit software.
The solution proved to be a combination of materials. A
preliminary design model was constructed using blocks for key
devices and adding a finned heatsink and air flow. As the design
evolved, a detailed model was created that included wiring,
individual resistors, capacitors and other components. Coolit
analysis determined the optimal fin shape, size and spacing.
It minimized heatsink size and quantified air flow requirements.
Coolit identified which fins were least effective. These fins
were removed, further reducing weight, while still keeping the heat
sink structurally strong and satisfying the cooling requirements.
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