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System in signals&system?

  1. Jul 10, 2012 #1
    how do we represent a system and what does it mean?how do we give inputs to it and meaning of delayed input?
    advanced thanks.
  2. jcsd
  3. Jul 10, 2012 #2


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    Staff: Mentor

    What kind of system? Analog, digital, time domain, frequency domain, etc.? Can you show us what you have been reading so far on the subject, and ask some more specific questions please?
  4. Jul 11, 2012 #3
    its is all about both analog and digital system in time domain.they gives the inputs in terms of phase shift of given signal i.e x(n-1) for digital and d/dt(x(t)).what these input represents and how?
  5. Jul 11, 2012 #4


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    this is about Linear System Theory (what they now call Signals and Systems). in either continuous-time (often called "analog") or discrete-time (often called "digital") systems, you have three fundamental blocks:

    1. adder (or subtracter), sometimes called a "summer". it adds two or more signals together.
    2. scaler (sometimes called "gain"). it multiplies a signal by a constant or coefficient.
    3. some form that can discriminate between signals with respect to frequency.
    3a) in analog systems, usually that device is represented as an integrator and has Laplace transform of 1/s
    3b) in digital (DSP) systems, that device is represented as a unit delay and has Z transform of 1/z

    you assemble these adders, scaler, and integrators or delays using one of several forms. the most common forms are the Direct Form I (DF1) or Direct Form II (DF2), but you'll see other forms. from those forms and from knowledge of the coefficients, you get a transfer function that fully describes the input/output relationship in a linear, time-invariant system.
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