[time-nuts] Speaking of Costas loops (WAAS)

[Magnus Danielson]

On 07/06/2013 06:29 PM, Joseph Gwinn wrote:
>>> Code/Carrier Frequency Coherence: The lack of coherence between the
>>> broadcast carrier phase and the code phase shall be limited. The short
>>> term (<10sec) fractional frequency difference between the code phase
>>> rate and the carrier frequency shall be less than 5x10-11 (one sigma).
>>> Over the long term (<100 sec), the difference between the change in the
>>> broadcast code phase (convert to carrier cycles) and the change in the
>>> broadcast carrier phase shall be within one carrier cycle (one sigma).
>>
>>
>> This is interesting. Does it imply that they regenerate the code on board?
>
> Very unlikely, because then the bird would have to understand every
> possible code, including those not invented when the bird was launched.

If it is within the Gold codes being used for GPS and WAAS, they only 
need to alter the 10 bit reset-value of the G2 PRN code. See the WAAS 
specification, as this method is being recommended for receivers.

Within that limit, it is relatively cheap to provide code tunability.

Cheers,
Magnus