shermaine

Hi guys,

I have a few question from pas yrs exam which i hope to check with you guys what's the correct answer. Can kindly advise me?

Q(1) signal Xa(t) = pi sin(5t + 6). By skecthing Xa(t) & Xa(t)^sq
(a) Average of Xa(t) =0
(b) Average power Xa(t) = 0
(c) rms value of Xa(t) is equal to sq 0.5 pi
(d) All the above

Q(2) Xa(t) = e^5e^j(6t + 7). By sketching Xa(t) and Xa(t)^2
(a) Signal has amplitude of e^5e^j7
(b) phase signal is given by factor e^j7
(c) both correct
(d) both wrong

Q(3) Does cos(2t) + e^jt & cos(2t) + e^t have fourier series?
(a) no for both
(b) yes for both
(c) yes & no
(d) none of the above

Q(4) Telephone speech has no bradd. Any signal from 0.3 to 3.4khz is transmitted. To restore the brass of the signal, so it will have better hi-fi.
(a) Square the signal so as to create dc or low fre
(b) pass the signal into equalizer to enhace low freq spectrum
(c) convolue the signal sinusoid having frd 0 to 3khz
(d)impossible to be done

Q(5) y(t) of a robot is input using x(t) applied to a motor according to dy(t)/dt + 3y(t) = 2x(t)
(a) system is a second orde
(b) freq response is the (a1 + a2jw)/(a3 +a4jw)
(c) impulse response of sinuoid
(d) none of the above

Q(6) Audio equalizer is used to compensate for variation in freq.CD band is divided into 5 band equalizer
Freq(hz) 100 300 1000 3000 10000
Gain(db) 0 0 0 0 0
(a) Output very small as gain are set to zero
(b) output same as input
(c) both are correct
(d) both are wrong

Pls advise me. Thanks!!!!

Nigel Goodwin

I suggest that if you provide the answers you think, people will comment on them - otherwise it looks like you're wanting it doing for you! (even if you're not!).

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Hero999

Another thing, try using Latex, it's not that hard to learn and makes your equations so much easier to read.
http://www.electro-tech-online.com/m...equations.html

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Get Opera it's simply a superb browser.

dknguyen

Is asking people to give you answers to your homework the only thing you ever do on this forum?

shermaine

Here's my answer:

(b)
(b)
(a)
(b)
(a)
(a)

can someone advise me which part of my answers are wrong?
Please kindly advise.Thanks.

dknguyen

the first one is wrong, because the power of a signal is defined as the average of the area beneath the curve formed by the SQUARED of the function. The average of the sinusoid function might be zero, but that's not how power is defined.

I think the second one is also wrong because for Xe^j(theta), theta is the phase and X (a real number) is the magnitude. The phase in this case varies with time since for j(theta), theta is time dependent.
http://mathworld.wolfram.com/Phasor.html

I agree with your answer for three, because the exponentials go on keep on increasing forever. But I might be confusing a fourier series with a fourier/laplace transform (unless the same rule applies for both in that the transform cannot exist if the function never dies off to zero, since the the integral cannot exist then). We never used the series in my classes too much so I don't remember much about them.

METHAMPHOSiST

What the hell? And I thought I was a nerd!