transponder implementation

hairybadger

hairybadger

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I've been idly wondering how transponders are physically implemented on the satellite. Extensive googling has left me none-the-wiser. I imagine the answer varies according to generation and model, but:
  • is each transponder a dedicated set of electronics that receives and transmits on a given frequency and polarity throughout the lifetime of the satellite?
  • is each transponder a logical set of transistors etc that can be allocated and deallocated as the need arises, so for example a given transponder can transmit at one frequency and then changed to another at the flick of a switch?
  • or something else entirely?
 
Good questions of which I'd like to know more about too. Originally I was under the impression each transponder had a dedicated set of electronics, but now we have virtual transponders to make things a little more complex.
 
Channel Hopper said:
This gives an idea of the Eutelsat W onboard stuff. No need to go much further than page 10
http://www.satplaza.com/orbit/handboek_w.pdf
Click to expand...
:) I get confused at the second line:

W1 is designed to provide 28 channels at saturation, W2, W3 and W5 are designed to offer 24 transponders at saturation and W4 is designed to provide 31 transponders at saturation
Click to expand...

Channels on W1, transponders on the others? What is the distinction?

Also - "at saturation"? If I have two questions after two sentences I think the document is too complicated for me :)
 
Channels here means transponders. Transponders are digital muxes anyway.

Saturation means full power.
 
The best description Ive ever seen described the transponder as a bent pipe in space.

It takes the incoming signal, frequency shifts it, does some amplification & literally turns its around for retransmission back towards the ground.
 
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