Hi Bob,
Thanks for your reply. I am trying to lock the system show in the figure
found on this link.
http://img19.imageshack.us/img19/826/dsssrxr.jpg
If S(n) = RxD signal which is modulated by a PN Sequence
1st step --> The input to Carrier Loop = S(n)*P(n), which the product of the
RxD signal and the PN Sequence assuming P(n) matches in phase.
2nd step --> The carrier tracked poptr(n) is the multiplied with RxD signal
S(n) to remove the carrier from it.
i.e. Input to Code Loop = S(n) * complex_conjugate(poptr(n))
Is this how you see the system?
Thanks
John
On Wed, Aug 4, 2010 at 3:07 AM, Bob McGwier <rwmcgw...@gmail.com> wrote:
> The SECOND ORDER Costas loop produces foptr(n) and poptr(n) which is the
> frequency and phase estimate for the carrier.
>
> sin(poptr(n)) is the estimated carrier.
>
> If S(n)*sin(poptr(n) is the spreading code modulating the estimated
> carrier, then
>
> S(n)*P(n) * complex_conjugate(S(n)*sin(poptr(n)) should be approximately
> P(n) up to error in
>
>
> a) your estimate of the carrier
>
> BUT ALSO
>
> b) the clock of the transmit system and its initial phase offset for the
> complex spreading code MUST ALSO be estimated to close this system and
> track. My little equation above ASSUMES perfect knowledge of S(n) which is
> NEVER the case in a real system.
>
> Bob
>
>
>
>
>
>
> On 8/3/2010 9:45 PM, John Andrews wrote:
>
>> Hi,
>> can someone guide me a little here please. I have a complex signal S(n)
>> that I multiply with a sequence P(n) of length N (the sequence consists
>> of {-1,1} ). I pass the product into a Costas Loop to track the carrier.
>> Btw, the complex_input signal a spread signal spread using the sequence
>> P(n) and BPSK modulated.
>>
>> S(n)*P(n) ---> Costas Loop
>>
>> Then I want to remove the carrier from the original signal which can be
>> done by multiplying the frequency output of the costas loop which is
>> foptr[i] with S(n). Is that right? I want to do this in GRC. Can someone
>> guide me a little here and tell me if I am understanding it right.
>>
>> Will be eagerly waiting for a reply. I am not good at Communications
>> stuff as this is not my major but I am trying hard. :) A little help
>> will greatly appreciated.
>>
>> Thanks
>> John
>>
>>
>>
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>
>
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