Mathematical Question from Signal Processing

Hi,

I am working on the following problem.

I have a function A(t) which is the "envelope" of a signal that satisfies the following conditions:

1) it is positive on an interval [a,b] 2) has a single maximum at the midpt of the interval 3) is symmetric about the maximum

I have some defined frequency w such that the period for this frequency, tau, is much smaller than b-a. Now I sample N points from the interval [a,b], t1,...tN. Although the points may not be uniformly sampled, we will assume that N is large (in the sense that the number of points per period is large, or in signal processing language, the signal has a high "oversampling factor"). I define the sum:

S1 = Sum from i=1 to N ( A(ti) )

and wish to consider the sum:

S2 = Sum from i=1 to N ( A(ti) cos(2*w*ti) )

I want to claim that S2 > tau, it follows that S2 will be very small.

QUESTIONS:

1) Is this argument correct if A was a Gaussian envelope? 2) How do I generalize this argument to handle more general envelopes that satisfy the conditions given above? I've tried considering Taylor series expansions of A about its maximum, but I can't seem to get anywhere.

Thank you very much,

Juno

Reply to
junoexpress
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This is two complicated for me to work on without a motivation. It reads to much like a side lemma in a math book.

Bill

-- Ferme le Bush

Reply to
Salmon Egg

I cannot believe how badly I spelled too and too.

-- Ferme le Bush

Reply to
Salmon Egg

"junoexpress" wrote in news: snipped-for-privacy@g47g2000cwa.googlegroups.com:

snip

good, keep working on your homework.

Reply to
me

Why make things more complex. Think. What is the maximum value of the cos(...) factor in each term.

Reply to
Don Kelly

That was my first impression also. If the second sum is the same samples, but some of them multiplied by a value less than one, and some others even negative, it would seem 'obvious' that the second sumation must be less than the first.

Exactly how much less would be a function of how often cos(2*w*ti) is not ==1. If the 'number of points per period is large', then the number of times that 'cos(2*w*ti)

Reply to
daestrom

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