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From: JAlbertoDJ on 21 Sep 2009 07:00

I am reading and you are confuse me. Differents between PLL ans FLL??
None.

In a PLL, VCO output is the frecuency recover, then you have a FLL.


I have done an AFC with a PLL. Error signal is get of this form:

x=FFT previous
y=FFT current

z = (complex conjugate of x) * y

frecuency estimated= (arg of z) * Fs / (2*pi)

Frecuency error= frecuency estimated - frecuency of bin FFT






From: Eric Jacobsen on 21 Sep 2009 12:37
On 9/21/2009 4:00 AM, JAlbertoDJ wrote:
> I am reading and you are confuse me. Differents between PLL ans FLL??
> None.
>
> In a PLL, VCO output is the frecuency recover, then you have a FLL.
>
>
> I have done an AFC with a PLL. Error signal is get of this form:
>
> x=FFT previous
> y=FFT current
>
> z = (complex conjugate of x) * y
>
> frecuency estimated= (arg of z) * Fs / (2*pi)
>
> Frecuency error= frecuency estimated - frecuency of bin FFT
>

You deleted the context, so there's no way to tell where this question
came from.

PLL is not equal to FLL. PLLs can be used to track frequency, but FLLs
don't lock phase. PLLs do lock phase. The distinction can be very
important.


--
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com
From: Tim Wescott on 21 Sep 2009 12:45
On Mon, 21 Sep 2009 09:37:15 -0700, Eric Jacobsen wrote:

> On 9/21/2009 4:00 AM, JAlbertoDJ wrote:
>> I am reading and you are confuse me. Differents between PLL ans FLL??
>> None.
>>
>> In a PLL, VCO output is the frecuency recover, then you have a FLL.
>>
>>
>> I have done an AFC with a PLL. Error signal is get of this form:
>>
>> x=FFT previous
>> y=FFT current
>>
>> z = (complex conjugate of x) * y
>>
>> frecuency estimated= (arg of z) * Fs / (2*pi)
>>
>> Frecuency error= frecuency estimated - frecuency of bin FFT
>>
>>
> You deleted the context, so there's no way to tell where this question
> came from.
>
> PLL is not equal to FLL. PLLs can be used to track frequency, but FLLs
> don't lock phase. PLLs do lock phase. The distinction can be very
> important.

And in the context of AFC for something like FM radio reception you don't
even have to lock the frequency - you just need to pull it in close
enough to the design center of the receiver to make things work correctly.

--
www.wescottdesign.com
From: robert bristow-johnson on 22 Sep 2009 03:22
On Sep 21, 12:37 pm, Eric Jacobsen <eric.jacob...(a)ieee.org> wrote:
> On 9/21/2009 4:00 AM, JAlbertoDJ wrote:
>
>
>
> > I am reading and you are confuse me. Differents between PLL ans FLL??
> > None.
>
....
>
> PLL is not equal to FLL.   PLLs can be used to track frequency, but FLLs
> don't lock phase.  PLLs do lock phase.  The distinction can be very
> important.

there is an inherent integrator in the loop in a PLL that is not in
the FLL. so the closed loop tracking behavior (step response,
whatever) for the PLL is different than the FLL.

my $0.02 . (i hadn't done a regular ol' PLL since my college daze.
but i have done an ASRC that has something similar in the loop. ya
know, maybe an ASRC *does* have a PLL in it. the step or stride
length is sorta like instantaneous frequency.)

r b-j
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