K
kirgizz
- Jan 1, 1970
- 0
Hello,
I'm dealing with synchronisation issue, that is a big problem for me.
I read some ebooks about PLL so I understand (theoretically) it
functionality.
My DSP must be able to generate (internally) a sine wave which is
frequency-locked to an external TTL reference signal with an error
about 0.01Hz (at 20kHz). The frequency range of the external signal i
20Hz-20kHz. I use the DSP in place of VCO, but it doesn't work proper.
More detailed:
ext. TTL signal -> PLL SIGin -> PFD -> Loop Filter -> ADC -> DSP ->
DAC -> Comparator -> PLL COMPin.
My problems are
1. External signal is variable (and I can't get some error-linearit
after
loop filter for the whole freq-range).
2. All commercial PLLs (such xx4046 and xx9046) are designed fo
MHz-range, and not for my little 20kHz.
Settling time is depending on the sampling frequency (not so good too?).
I read about software PLL and I think that it's too complex to implemen
for frequencies up to 20 kHz.
ADPLLs...hmmm, I can't imagine, how I use it form my design (I mea
available xx297 PLLs), but I'd rather do all digitally.
Can you help me with an advice how I do this synchronisation?
Maybe there are another ways to do it.
Thank you in advance
kirgizz
I'm dealing with synchronisation issue, that is a big problem for me.
I read some ebooks about PLL so I understand (theoretically) it
functionality.
My DSP must be able to generate (internally) a sine wave which is
frequency-locked to an external TTL reference signal with an error
about 0.01Hz (at 20kHz). The frequency range of the external signal i
20Hz-20kHz. I use the DSP in place of VCO, but it doesn't work proper.
More detailed:
ext. TTL signal -> PLL SIGin -> PFD -> Loop Filter -> ADC -> DSP ->
DAC -> Comparator -> PLL COMPin.
My problems are
1. External signal is variable (and I can't get some error-linearit
after
loop filter for the whole freq-range).
2. All commercial PLLs (such xx4046 and xx9046) are designed fo
MHz-range, and not for my little 20kHz.
Settling time is depending on the sampling frequency (not so good too?).
I read about software PLL and I think that it's too complex to implemen
for frequencies up to 20 kHz.
ADPLLs...hmmm, I can't imagine, how I use it form my design (I mea
available xx297 PLLs), but I'd rather do all digitally.
Can you help me with an advice how I do this synchronisation?
Maybe there are another ways to do it.
Thank you in advance
kirgizz