From: Capt. Convolution on
On Tue, 18 May 2010 08:29:59 -0700 (PDT), dbd <dbd(a)> wrote:

>On May 18, 1:26�am, "Zhi.Shen" <zhi.m.s...(a)> wrote:
>> Hi, Friends!
>> �Does anyone read Mr. Fredric Harris's book
>> "Multirate signal processing for communication systems" ?
>> �I think it's a good book for engineering,
>> but some descriptions make me confused.
>> On page 53, Chapter 3
>> "For a specific example, the filter presented in Figure 3.20 designed for
>> 60dB side-lobe levels is used in a 32-to-1 down sampling application. If the
>> side-lobes are equiripple at 60-dB the integrated side-lobe level is -36.1dB
>> which, when distributed over the remaining bandwidth of 1/32 (-15.1 dB) of
>> input sample rate, results in an effective alias side-lobe suppression
>> of -51 .2dB, equivalent."
>> Who knows the "integrated side-lobe level"'s meaning?
>That's the name of the integral of the filter response across all the
>sidelobes in the stopband.
>> And why it's "-36.1dB "?
>That's the calculation of the integral of the filter response across
>all the sidelobes in the stopband.
>Dale B. Dalrymple

Hi Mr. Dalrymple,
Thank you for your post. I would also like to understand the
origin of the -36.1 dB value.

A "dB" measurement is "X db = 10*log10(P1/P2)". In this case, will
you please tell what are the values of P1 and P2, and how P1 and P2
are computed (determined), in that -36.1 dB measurement?

Thank you very much.
Capt. Convolution
From: Capt. Convolution on
On Thu, 20 May 2010 17:23:58 -0700 (PDT), dbd <dbd(a)> wrote:

>On May 20, 3:24�pm, Capt. Convolution <C.Convolut...(a)> wrote:
>> That web site appears to be strickly some Asian language. �I tried
>> examining the Amazon English version of the book but was unable to
>> learn anything about "integrated side-lobe level".
>> Capt. Convolution

Hello Mr. Dalrymple,

>Have you tried
>intrgrated sidelobe level
>on Google?

Only in the most cursory way.

>Try equation 1 in:
>Phase Coded Waveforms for Radar

That URL didn't work for me. but the following did work

Unlike the other papers, the above "05_0112.pdf" paper defines
"integrated sidelobe level" in terms of the time-domain output
waveform of a matched filter. I don't know if that makes sense or
not. Maybe it does. However, in the paragraph above their equation
1, the authors say: "The matched filter is a noisy signal that
produces relatively large time sidelobes". I can't understand what
kind of thinking would cause three authors agree to say "a filter is a
signal". What a strange, odd, thing to say!

>Try equation 2 in:

The above PDF file is almost identical to the paper provided by Mr.
Zhi.Shen (
The above "134127.pdf" equation 2 is identical, in every way, to the
equation 2 in the "123417.pdf" file. (The two papers were written by
the same people and their textual descriptions of their two equation
2's are word-for-word identical.

>Try equation 3 in:
>Simulation and Analysis of Pulse Compression for Weather Radars ...

The "00519643.pdf" paper defines "integrated sidelobe level" in a
manner very similar to the "123417.pdf" paper. However, it's not
clear to me if those similar definitions are talking about the
spectrum of a signal or the frequency response of a filter. (None of
the papers say anything about the impulse response of a filter.)

Apparently the authors of these papers assume their readers are well
versed in radar signal processing and a very-careful definition of
"integrated sidelobe level" is not necessary in their papers.

In any case, thank you thank Mr. Dalrymple for helping me investigate
this notion of "integrated sidelobe level" in my attempts to
understand the dB values given in Fred Harris' book.

>If you get around to actually trying a calculation, let us know. Tell
>us what you have done, why and what, if any, questions remain.

I confess that I have not yet done any software modeling of
"integrated sidelobe level" when the output of a filter is decimated.
I hope to do that in the next week. If I learn something definitive,
something predictable and sensible, I will most assuredly post my
results for you and Mr. Zhi.Shen to see. Thanks again.

Capt. Convolution.
From: Capt. Convolution on
On Fri, 21 May 2010 08:02:17 -0700 (PDT), dbd <dbd(a)> wrote:

>If you had tried Google in a more than cursory way you might have
>noticed that there are even a number of different definitions of
>"integrated sidelobe level". The choice between them depends on the
>nature of the signal you are analysing, the type of analysis you are
>trying to perform and what the purpose of your use of "integrated
>sidelobe level" will be. Until you can communicate that, no one can
>give more than a general answer. I suggest the effort at modeling to
>force you to face and make some of those choices. That could give you
>more specific questions.
>Dale B. Dalrymple

Yes I understand.

Thank you again,
Capt. Convolution
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