> Hi,
> I am studying an equalizer which uses a lead-lag compensator after a
> high frequency attenuated distortion. At first, it seems quite simple:
> The equalizer emphasizes high frequency gain to make the total response
> flat at the high frequency part. When I try to get the total impulse
> response, I find that the impulse response of the lead-lag filter
> (nominator:[2.5e10, 1], denominator:[1.0e10, 1]) has a negative
> response. This is the first time I have a negative impulse response in
> contrast to the normal positive impulse response. I guess that it is
> because the high frequency pass feature.
Yes. Anything high-pass will have that tendency. The extreme case is a
1st-order DC blocking filter, which has a positive-going impulse, then a
negative-going exponential decay with area equal to the impulse.
> The further problem is that the total impulse response of the low pass
> channel and the equalizer is still a negative impulse response. On the
> other hand, I do not see the equalized result has inversed the signal in
> the Simulink simulation model. How to explain the contradictory?
>
> Please help me if you have the answer. Thanks.
Probably what's going on is that the equalization is either not complete
or not exact, so the high-pass filter is "showing through". Then the
nature of the signal is such that it does not have a lot of content in
the higher frequencies.
The incomplete equalization is what makes for the negative-going bit in
the impulse response. The signal's shape coupled with the final channel
response is what makes for no negative-going elements in the resulting
output signal.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Reply by fl●May 20, 20142014-05-20
Hi,
I am studying an equalizer which uses a lead-lag compensator after a high frequency attenuated distortion. At first, it seems quite simple: The equalizer emphasizes high frequency gain to make the total response flat at the high frequency part. When I try to get the total impulse response, I find that the impulse response of the lead-lag filter (nominator:[2.5e10, 1], denominator:[1.0e10, 1]) has a negative response. This is the first time I have a negative impulse response in contrast to the normal positive impulse response. I guess that it is because the high frequency pass feature.
The further problem is that the total impulse response of the low pass channel and the equalizer is still a negative impulse response. On the other hand, I do not see the equalized result has inversed the signal in the Simulink simulation model. How to explain the contradictory?
Please help me if you have the answer. Thanks.