Microwave - Standard Intermediate Frequency?
The early satellite TV receivers used a 70 MHz IF, to filter and amplify and limit the down converted signal.

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On the other hand, in the 1970s, there were satellite to satellite laser links, and the data streams ended up on earth and were recorded onto photographic film. To handle the downlink (not the space-based laser links), some radio methods were needed to handle clouds and other non-laser friendly issues.

The datarate was 700,000,000 bits per second.

I don't think 70MHz IFs (with +-5MHz bandwidth?) would suffice.

I do recall various MODEMS (back then, we called them bit-syncs) crafted to handle 150,000,000 bits per second in the early 1970s using ECL; some in the late 1970s even were adaptively equalized, using coax-delays and Gilbert-cell multipliers; these also functioned at 150,000,000 bits per second.

In the late 1970s I recall boxes providing nearly 1/2 GigaBit spaceborne. These likely used 5x or 10x the bitrate as the carrier, just so the antenna bandwidth and the antenna beam-forming, were practical.