Timing recovery and Carrier recovery

[Davy]

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

 

[john]

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

 

[Steve Underwood]

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

 

[Vladimir Vassilevsky]

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

 

[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

 

[john]

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.

 

[Jerry Avins]

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

 

[Vladimir Vassilevsky]

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

 

[Jerry Avins]

Jerry Avins wrote:




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

At comp.dsp, we give advice gratis.

Jerry

 

[Vladimir Vassilevsky]

At comp.dsp, we give advice gratis.

It looks like cheap advice very often.

VLV

 

[Jon Harris]

Vladimir Vassilevsky 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.

I agree. It also tends to decrease the signal to noise of the newsgroup.

 

[Stan Pawlukiewicz]

At comp.dsp, we give advice gratis.

Sometimes too gratis

 

[Jerry Avins]

It looks like cheap advice very often.

Here, one gets at least what one pays for!

Jerry

 

[Richard Owlett]

Vladimir Vassilevsky writes:
[MUCH]

Dear Sir:

If you posted with a valid email address, I would have my say privately.

Please "wake up and smell the roses".

You may have technical skills, but your interpersonal skills resemble
mine in the midst of the last century ( PS that aint no complement ).

My email is valid if you would like a *PRIVATE* discussion.

Richard Owlett
Springfield, MO USA

 

[Vladimir Vassilevsky]

Richard Owlett wrote:

If you posted with a valid email address, I would have my say privately.

Please "wake up and smell the roses".

You may have technical skills, but your interpersonal skills resemble
mine in the midst of the last century ( PS that aint no complement ).

My email is valid if you would like a *PRIVATE* discussion.

I have to suggest that you may have wonderful interpersonal skills but
your technical skills are likely not to improve since the midst of the
last century. Did you mean throwing some kind of challenge or it is all
just the idle talk?

VLV

 

[Richard Owlett]

Richard Owlett wrote:




I have to suggest that you may have wonderful interpersonal skills but
your technical skills are likely not to improve since the midst of the
last century. Did you mean throwing some kind of challenge or it is all
just the idle talk?

VLV

I tried.
VLV's interpersonal skills <<<<<<< my technical skills