Timing recovery and Carrier recovery

Hi all,

I am studying digital receiver and confused with timing recovery and
carrier recovery. I think carrier recovery should be done in front of
timing recovery in analog receiver i.e. [Carrier recovery] -> [Timing
recovery].

Is carrier recovery mean eliminate the carrier frequency and transform
signal to band-limited symbol?

Is timing recovery mean sample the band-limited symbol?

But in digital receiver, the procedure be
[Timing recovery] ...-> [Equalizer and Carrier recovery]? What's it
mean?

Can you recommend some tutorial on this subject?

Best regards,
Davy

Davy wrote:
> Hi all,
>
> I am studying digital receiver and confused with timing recovery and
> carrier recovery. I think carrier recovery should be done in front of
> timing recovery in analog receiver i.e. [Carrier recovery] -> [Timing
> recovery].
>
> Is carrier recovery mean eliminate the carrier frequency and transform
> signal to band-limited symbol?
>
> Is timing recovery mean sample the band-limited symbol?
>
> But in digital receiver, the procedure be
> [Timing recovery] ...-> [Equalizer and Carrier recovery]? What's it
> mean?
>
> Can you recommend some tutorial on this subject?
>
> Best regards,
> Davy

There are many ways to implement a "digital receiver", and there are
many definitions of that term. You need to be more specific. What kind
of modulation are you dealing with?

Carrier recovery does not bandlimit the signal, it removes residual
frequency and phase offset so the constellation stabilizes. Timing
recovery is a synchronous decimation process where the signal is
downsampled to one sample per baud, and that sample is taken at the
instant where the SNR is maximized, ie at the the peak time of the eye
pattern. This normally involves interpolation between adjacent samples.

Timing recovery can be and often is performed before carrier recovery,
because it is often possible to determine the ideal sampling instants
in the presense of a residual carrier.

There are many references on this. Try searching on google.


John

Hi Davy,

Carrier recovery, or tracking, does not necessarily mean eliminating the 
carrier, although that is generally the goal. It means working out 
exactly what the carrier is - its precise frequency and phase - and 
usually creating a precise copy of the original.

Timing recovery means working out the exact positions of the symbols 
within the signal stream. Various algorithms allow this to be done ahead 
of precise carrier recovery. This means a lot of digital receivers look 
something like:

    use the carrier to get to baseband -> perform timing recovery -> 
equalise the signal -> perform carrier tracking and feed that back to 
tune the first stage -> demodulate the symbols

while others look like:

    use a rough approximation of the carrier to get to baseband -> 
perform timing recovery -> equalise the signal -> perform carrier 
tracking and remove the last traces of the carrier from the signal -> 
demodulate the symbols

The first time you approach this it might seem a little weird that you 
can track the symbol timing without having tied down the carrier 
precisely. However, a number of really simple algorithms - e.g. Gardner 
- allow this.

Regards,
Steve


Davy wrote:

>Hi all,
>
>I am studying digital receiver and confused with timing recovery and
>carrier recovery. I think carrier recovery should be done in front of
>timing recovery in analog receiver i.e. [Carrier recovery] -> [Timing
>recovery].
>
>Is carrier recovery mean eliminate the carrier frequency and transform
>signal to band-limited symbol?
>
>Is timing recovery mean sample the band-limited symbol?
>
>But in digital receiver, the procedure be
>[Timing recovery] ...-> [Equalizer and Carrier recovery]? What's it
>mean?
>
>Can you recommend some tutorial on this subject?
>
>Best regards,
>Davy
>
>  
>

Davy wrote:
> Hi all,
> 
> I am studying digital receiver and confused with timing recovery and
> carrier recovery.

Keep studying.


  I think carrier recovery should be done in front of
> timing recovery in analog receiver i.e. [Carrier recovery] -> [Timing
> recovery].

No. The carrier recovery should be done jointly with the timing recovery.

> Is carrier recovery mean eliminate the carrier frequency and transform
> signal to band-limited symbol?
> 
> Is timing recovery mean sample the band-limited symbol?

There is a special newsgroop: help.moro

> But in digital receiver, the procedure be
> [Timing recovery] ...-> [Equalizer and Carrier recovery]? What's it
> mean?
> 
> Can you recommend some tutorial on this subject?
> 
> Best regards,
> Davy
> 

Hi Steve,

Thank you for your help :-) and I really find it a little weird.

I searched "Gardner timing recovery" in scholar.google.com and find
"Interpolation in digital modems-Part I: Fundamentals". Is it the
paper talk about timing recovery without having tied down the carrier?

And can you recommend a book talk about "digital receiver" thoroughly?
Thanks!

Best regards,
Davy

Davy wrote:
> Hi Steve,
>
> Thank you for your help :-) and I really find it a little weird.
>
> I searched "Gardner timing recovery" in scholar.google.com and find
> "Interpolation in digital modems-Part I: Fundamentals". Is it the
> paper talk about timing recovery without having tied down the carrier?
>
> And can you recommend a book talk about "digital receiver" thoroughly?
> Thanks!
>
> Best regards,
> Davy

That's a great paper to read, and so is Part II.

Vladimir Vassilevsky wrote:

   ...

> There is a special newsgroop: help.moro

   ...

You often have useful tidbits to impart. When you have nothing useful to 
say, it is best to just say nothing. Regularly sneering at those who 
know less than you gives the impression that you're insecure.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

On 6 Jan 2006 01:01:06 -0800, "Davy" <zhushenli@gmail.com> wrote:

>Hi Steve,
>
>Thank you for your help :-) and I really find it a little weird.
>
>I searched "Gardner timing recovery" in scholar.google.com and find
>"Interpolation in digital modems-Part I: Fundamentals". Is it the
>paper talk about timing recovery without having tied down the carrier?
>
>And can you recommend a book talk about "digital receiver" thoroughly?
>Thanks!
>
>Best regards,
>Davy

Check these books out:
http://www.dspia.com/bookstore.html
Especially this one: "Synchronization, Channel Estimation, and Signal
Processing V2 Digital Communication Receivers"

HTH.

Jerry Avins wrote:


> You often have useful tidbits to impart. When you have nothing useful to 
> say, it is best to just say nothing. Regularly sneering at those who 
> know less than you gives the impression that you're insecure.

When I will need your advice, I will certainly ask for it.

VLV

Vladimir Vassilevsky wrote:
> 
> 
> Jerry Avins wrote:
> 
> 
>> You often have useful tidbits to impart. When you have nothing useful 
>> to say, it is best to just say nothing. Regularly sneering at those 
>> who know less than you gives the impression that you're insecure.
> 
> 
> When I will need your advice, I will certainly ask for it.

At comp.dsp, we give advice gratis.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������