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

jmfranke jmfranke at cox.net
Sat Jul 6 18:09:22 UTC 2013


A lot of the changes from "bent pipe" to the new system including C-band 
uplink is explained here:

http://www.insidegnss.com/node/697


While there, downlink the extended PDF version.

John  WA4WDL
--------------------------------------------------
From: "Magnus Danielson" <magnus at rubidium.dyndns.org>
Sent: Saturday, July 06, 2013 12:57 PM
To: <time-nuts at febo.com>
Subject: Re: [time-nuts] Speaking of Costas loops (WAAS)

> 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
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