[SI-LIST] Re: what's de-emphasis
- From: Michael Greim <mgreim001@xxxxxxxxx>
- To: Adiu <adiu_panli@xxxxxxxxx>
- Date: Fri, 30 Oct 2009 15:25:09 -0500
If you google with a little more gusto you will get what you
want.
In short, pre-emphasis modifies a waveform such that the
interconnect distortion is effectively canceled out. In short, and in an
ideal
world, the signal at the receiver looks remarkably like what
was presented at the front of the pre-emphasis circuit.
Then there's
http://www.the-signal-and-power-integrity-institute.com/Pre-emphasis2.pdf
Here is what wikipedia says when you google with gusto.
In high speed digital transmission, pre-emphasis is used to improve signal
quality <http://en.wikipedia.org/wiki/Signal_integrity> at the output of a data
transmission <http://en.wikipedia.org/wiki/Data_transmission>. In
transmitting signals at high data rates, the transmission medium may
introduce distortions, so pre-emphasis is used to distort the transmitted
signal to correct for this distortion. When done properly this produces a
received signal which more closely resembles the original or desired signal,
allowing the use of higher frequencies or producing fewer bit errors.
On Fri, Oct 30, 2009 at 3:09 PM, Adiu <adiu_panli@xxxxxxxxx> wrote:
> Hello, Everyone
>
> What's pre-emphasis and de-emphasis?
> I can get the following definitions from Google:
>
> Pre-emphasis: " Improving the signal to noise ratio by increasing the
> magnitude of higher frequency signals with respect to lower frequency
> signals"
> De-emphasis: " Improving the signal to noise ratio by decreasing the
> magnitude of higher frequency signals with respect to lower frequency
> signals"
>
> There is not problem to understand the above definitions. However, I have
> difficulities in the following concerns:
> 1. is pre-emphasis always at the transmitter?
> 2. is de-emphasis always at the receiver?
> 3. what's difference between de-emphasis and equalization?
> 4. I have not problems to draw the pre-emphasis pulse waveforms with
> respect to a normal waveform. However, I am not quite sure of the
> de-emphasis pulse waveforms. The attached figure shows a simple example.
> Could someone confirms for me if the waveforms are draw correctly?
>
> any comments are appreciated.
>
> best regards,
> adiu
>
>
>
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Best Regards,
Michael C. Greim
And all this science they don't understand
Is just my job six days a week.....
We will either find a way or make one -Hannibal
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