Saturday, February 4, 2012
HW 2 Problem 19.3
I find that my equivalent circuit model for part A is identical to Figure 19.22, with a different tank network, and hence a different H(s). Because L and C are in parallel, Vc(t) (or Vs(t) depending on which figure you are looking at) equals Vr(t), making H(s) equal to one. This would then make M, which was equal to Eq. 19.27, solely equal to 8/(pi^2), which would not depend on Qe and F. Any ideas on how I am doing this so drastically wrong? Thanks
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1 comment:
Hi Rob,
I wouldn't say you are drastically wrong. H(s) = 1 is correct. As you mentioned the resonant tank is in parallel. Z_in(s) = Z_out(s) making H(s) = Z_out(s)/Z_in(s) = 1. In order to find M in terms of Q_e and F, you need to do the following calculation:
M = V/V_g = V/V_r1 * V_r1/V_s1 * V_s1/V_g
The important term is V_s1/V_g. Since the resonant tank is current-fed, your input port model should be a dependent voltage source (2*V_s1/pi)*cos(phi_s); where phi_s is the phase of the input impedance Z_in(s). Once the terms are multiplied through, you should have a result of M = 1/cos(phi_s). From there, I suggest taking a look at the 2010 posts. Those guys covered this problem pretty well, just don't believe everything you read (that goes for this post too!).
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