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Homework Help: RC Networks and complex numbers

  1. Feb 1, 2012 #1

    I maybe should have put this in the maths section, but it is related to electronics, so I figured here.

    I am reading Microwave Engineering by Pozar, and in one of the examples, it says that the series RC load impedance is ZL = 60 - j80, so the resistance is 60 Ohms and the capacitance is 0.995pF. But is doesn't expalin how that C value was arrived at.

    I was initially thinking that this was arrived at by comverting to polar form, but that doesn't seem to be it.

    Could someone please help me with this?


  2. jcsd
  3. Feb 1, 2012 #2
    The impedance of a capacitor is given by,
    which given a RC network, would be associated with the imaginary component on the complex plane.
  4. Feb 1, 2012 #3
    Thanks :)

    Okay, so, I know the frequency is 2GHz, which gets me ω. But what is Zc, is that the 80 in the complex number?

  5. Feb 1, 2012 #4
    Yes. The impedance of a network is given in the form Z=R+jX, where resistances are the real parts, and inductors and capacitors are the imaginary part. By plugging your values into the equation I gave you, you will indeed see that it is -j80!
  6. Feb 1, 2012 #5
    I get it now.

    Many thanks!

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