Yes, in order to equalize group delay, you need to know what to
equalize. But with an educated guess as to the system response, he could
get close.
All this said, in 2012, I would rather the amplifier be simple gain, the
inductor not loaded with capacitance and the filtering done past the
amplifier. We aren't living in the era of 3 transistor circuits.
When delta-sigma converters came on the scene. I wisely found new design
skills. [They replaced much analog filtering.] So better just to do the
filtering in DSP IF there is no critical power budget.
On 3/17/2012 6:25 AM, Attila Kinali wrote:
On Sat, 17 Mar 2012 06:13:28 -0700
gary<li...@lazygranch.com> wrote:
On 3/17/2012 5:44 AM, Attila Kinali wrote:
On Sat, 17 Mar 2012 10:15:17 +0000
"Poul-Henning Kamp"<p...@phk.freebsd.dk> wrote:
Either you need to characterize the exact behaviour of your filter
and build the necessary compensation for its phase/frequency behaviour
into your receiver, or you need a very flat filter (both freq+phase)
in order to reliably recognize the proper zero-crossing to track.
BTW: how do you compensate for the filter characteristics of your
magnetic loop antenna?
Any filter's group delay can be equalized by all pass filters.
Delay builds up at the filter corner. Since everything in the real world
is causal, you add delay outside that corner frequency but in the
passband to equalize it. This is to say, you can't remove delay, but
just add it to flatten out the group delay.
Sorry, i asked in a misleading way. I didnt mean to ask what technique
to use to flaten the phase delay, but rather how does phk know how the
compensating filter should look like? For this, one needs to exactly
characterize the antenna-amplifier chain...AFAIK
Attila Kinali
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