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Digital FPV video for drone racing
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dmills:
The nice thing about microwave is that a lot of the RF is just shapes on a bit of Duroid or Isola.

No need for much integration in the front end, do something like a printed interdigital filter followed by some gain (MMIC with 1/4 wave line for bias) and a diode mixer, then some more printed filter... LO multiplier chain can be not so very different with some MMIC to provide the power to the mixer, start with something low phase noise like a driscoll oscillator or such. Print the aerials on the back of the board. 

I figure a 5Ghz to 1Ghz transverter is only a handful of parts on a suitable board, and that none of them need to be highly integrated. Once you are down to a GHz the field of suitable mixers and demodulators opens right up.

TI, Analogue and Linear make good money by taking the design out of RF projects, but that is not the only way to roll.

Regards, Dan.
Marco:
You'll still need a ~5 GHz synthesizer, already a boutique part to start with.
hexahedron:
Ok, update time! I'm seeing a LOT of discussion about WiFi, and I would like to talk about that.
For a minute, let's imagine a world where wifi is legal for drone racing, and that most pilots use it. There is another competition I would like to talk about as an example. FTC. FTC (first tech challenge) is a competitive robotics program that uses 2.4Ghz wifi for all communications with the robot. Now, what does an FTC competition look like, purely from the perspective of the communication protocol? Well, firstly, there are always at least 2 people with specialized wifi scanners finding anyone that has wifi enabled on a device not used for the robot control system. When these inspectors find said people, they are asked to turn off their wifi or leave. This is already not a good sign. Before every match, each team (4 in total) are assigned a wifi band, and they will only have their wifi turned on, on that band for the duration of the match. During the match, the 2 devices (controller and robot) are never more than 15 feet away from the each other. Even with this extremely well organized and controlled system, nearly 25% of the matches have some sort of disconnection issue related to wifi. Here's why.
As you can see in this image, out of the 14 wifi bands available, only 4 do not overlap, and even when an organized system is in place to make sure the 4 contestants are on these 4 non-overlapping bands, there are STILL connection issues (yes, all the systems use WiFi direct).
Now take a moment to imagine trying to have 8 direct wifi connections going on at the same time, where the connection distance is often very large (depending on the track). Need I say more?
radar_macgyver:
I meant 802.11a where the chances of overlapping bands is much less of a problem.
hexahedron:
So, now that we know that we can't use 2.4Ghz wifi for this project, let's look at what we can use. Firstly, I would like you to recall the target audience for this product, MultiGP drone racers. Here is a link to the official rules: https://docs.google.com/document/d/16UYizESQ2ydsoO81ipasLb6IVkmiJKcattWiLboVm9M/edit#
I would like you to turn your attention to pages 8 and 9. Page 8 tells us that

"There are NO spec requirements on the following components:"
"Camera (Example: Runcam, Foxeer)"

page 9 tells us that:

"When constructing your MultiGP Spec Class Racer, you may pick one (1) component from each of the following categories:"

"3.2.3 VTX" (video transmitter)
"TBS UNIFY HV RACE"
"IRC TRAMP HV (with or without NFC board)"

Now, from that information, I hope we can all conclude that any video transmitter other than the 2 listed is out of the question.
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