Re: [Starlink] Main hurdles against the Integration of Satellites and Terrestial Networks

[David Lang <david@lang.hm>]

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On Sat, 16 Sep 2023, Ulrich Speidel via Starlink wrote:

> On 15/09/2023 11:29 pm, Alexandre Petrescu via Starlink wrote:
>> 
>> I must say that I dont know whether the original 'DISHY' is simply a
>> dish antenna with an analog amplifier and maybe some mechanical motor
>> steering, or whether DISHY includes a computer to execute some protocol,
>> some algorithm.

In addition to that Ulrich says, the dishy is a full computer, it's output is 
ethernet/IP and with some adapters or cable changes, you can plug it directly 
into a router.

There are numberous teardown videos on youtube now, for both the original and 
the 1st of the rectangular dishys, they will show you how complex the system is.

David Lang

  >
> It's a phased array, not a dish, even if it looks like one. It consists of 
> 100's of fingernail-sized antenna elements that:
>
> * during transmissions, have an individual phase delay added to the
>   signal transmitted from that element, in order to permit
>   transmission of the combined signal from all elements into a
>   particular direction.
> * during reception, have an individual phase delay added to the signal
>   collected by that element, before the signals are added to obtain
>   the combined received signal. This allows reception from a
>   particular direction.
>
> Dishy's main direction of transmission / reception is therefore not its 
> surface normal - this simply points to the area of the sky where Dishy 
> expects to see most satellites (a function of geographical latitude and 
> constellation design - essentially straight up in the tropics, and elsewhere 
> in the direction of the 53rd parallel, which corresponds to the predominant 
> orbital inclination in the Starlink fleet). The actual tracking is then done 
> with the phased array without mechanical movement by Dishy.
>
> From what I've seen, Dishy seems to consume more power on receive than on 
> transmit - that's if you actually download stuff. This is somewhat 
> counter-intuitive if you're used to putting link budgets together. But I'd 
> attribute that to a higher degree of digital signal processing required on 
> the receive and demodulation path.
>
>

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