Re: PLL Basics

On Feb 14, 8:30 am, Jerry Avins <j...@xxxxxxxx> wrote:
Muzaffer Kal wrote:
On Fri, 13 Feb 2009 11:36:50 -0500, Jerry Avins <j...@xxxxxxxx> wrote:

Of course filters are used in a PLL implementation. That doesn't mean a
PLL is a filter, any more it is a VCO.

I'm curious as to how you make the distinction. What makes a PLL a
non-filter? It has an H(s), it takes a noisy periodic signal and
produces cleaned up, frequency shaped version of it. How is that
qualitatively different from an RC filter?

It's also a signal generator, no? The OP asked a a simple,question that
(it seemed to me) embodied a misconception that I tried to dispel. To
answer your question, a simple RC filter isn't bandpass.

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

It's like a differentiator but for the phase. So you cannot think of
the original signal as input if you want this type of analogy.

Hardy
.

Relevant Pages

  • Re: AM radio receiver - design
    ... normal AM radio up to the detector and the PLL is added at that point. ... In the circuits I've mess about with, the reference oscillator or ... a VCO runs at twice the 455KHz number putting it at 910AM where it ... the gain on the VCO filter. ...
    (sci.electronics.design)
  • Re: Receiver bandpass filter questions.
    ... >>I don't know much about filter design, ... basically a PLL with a logic output when the thing ... >>phase comparator output as an indication of lock. ... A PLL consists of a voltage controlled oscillator (VCO), ...
    (sci.electronics.basics)
  • Re: PLL Basics
    ... I know that a PLL uses in internal low pass filter. ... Since linear ramps aren't very interesting we can ignore it, and just consider the variations from the ideal ramp. ... N.B. The two integrators we need for a Type II system come from the VCO (which acts like an ideal integrator: a constant input voltage results in a constantly ramping (phase) output) and the loop filter. ...
    (comp.dsp)
  • Re: PLL Basics
    ... Given those conditions and considering those aspects, a PLL has filter-like behavior. ... This lowpass filter thing is nonsense and irrelevant. ... A modulation analyser or spectrum analyser is the test equipment of choice. ... The frequency multiplier model is nice as a simplistic introduction, but has limited utility if you want to specify or design for a particular performance level. ...
    (comp.dsp)
  • Re: PLL input filter vs. loop filter
    ... the low-pass filter on the output of the phase detector determines ... the agility of the PLL. ... loop filter when you have an input signal. ... If you continue to miss input signals, ...
    (sci.electronics.design)