Difference between revisions of "FM Homework Assignment Questions"
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:'''Answer 3:''' <blah blah> | :'''Answer 3:''' <blah blah> | ||
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| + | '''Question 4:''' The assignment seems a little ambiguous, as the specs just indicate that the maximum absolute value of the message signal must be less than 1. | ||
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| + | :'''Answer 4:''' You are right. In fact, the random message signal should be normalised so that its maximum absolute value is always 1. Therefore please do this in your simulation. | ||
==See Also== | ==See Also== | ||
Revision as of 23:14, 11 April 2008
Introduction
Please feel free to use this page like a message board to ask any questions you like about the FM homework assignment.
Questions and Answers (Q&A)
Question 1: I have been trying for days, using the bilinear transform (matlab: bilinear) to convert the filters from continuous time domain to discrete time domain. For the butterworth filter, I even used the butterworth function provided by matlab (matlab: butter). Nothing worked, the frequency responses always showed a difference of about a factor of 10. I then stumbled across another discretisation method from the Control Systems Toolbox: c2d. For the first two filters, I simply used a bilinear tustin approximation ( Hn = c2d(Hn_a,ts,'tustin') ) and for the third filter, I used the bilinear tustin approximation with prewarping, as with higher frequencies, the prewarping effect is more visible ( H3=c2d(H3_a,ts,'prewarp',omega_c3) ) The approximation using a zero order hold also works, but the prewarp is more accurate. My question now: Is it mandatory that we use the bilinear() function, or is the above described method okay?
- Answer 1: <blah blah>
Question 2: Is the equation for the reference signal at the top of page 3 of the assignment? (v(t) = ...) I'm trying to integrate to get phi(t) but the integral of the message signal is always zero.
- >> syms t;
- >> sin_m_of_t = sin(2*pi*2000*t);
- >> int(sin_m_of_t, 0, 277775)
- ans = 0
so that implies that for the sinusoidal input v(t) = A + n_c(t) + j*n_s(t)? It is just a sine wave though, so I suppose it does make sense that its integral over a whole number multiples of 2*pi is zero. Also, is my upper limit on the integral correct? ( = delta * (number of samples - 1))
- Answer 2: <blah blah>
Question 3: In section 6 it says v_ref is the value of v_o with no added noise. Does that imply that v_ref = message_signal, because isn't the message signal simply the demodulated output signal without noise?
- Answer 3: <blah blah>
Question 4: The assignment seems a little ambiguous, as the specs just indicate that the maximum absolute value of the message signal must be less than 1.
- Answer 4: You are right. In fact, the random message signal should be normalised so that its maximum absolute value is always 1. Therefore please do this in your simulation.
