communication basics

Discussion in 'Wireless & RF Design' started by raks_universe, Mar 22, 2010.

  1. raks_universe

    Thread Starter Active Member

    Mar 15, 2009
    What does complex quantity present in the signal represents,,,,,,,

    why we use complex terms in signal.....

    and im so confused with this complex quantity,,,,In communication too we r taking complex envelope etc.

    what is need for using complex variables...

  2. Papabravo


    Feb 24, 2006
    The use of complex numbers and complex algebra allows us to deal with behavior that would otherwise be difficult to describe and keep track of. It accurately describes the effect on AC voltage and AC current of reactive components. The properties of the imaginary unit (i or j) make the calculations come out correctly.

    If you know of another, simpler method of doing the same thing, then by all means tell us. I'm all ears!
  3. Duane P Wetick

    Senior Member

    Apr 23, 2009
    Probably the simplest explanation is that there are phase orientations involved in adding AC signals, thus the need for complex numbers when signals are combined; modulated for another word.

    Cheers, DPW [ Everything has limitations...and I hate limitations.]
  4. Thevenin's Planet

    Active Member

    Nov 14, 2008
    This is a good suject in which I was baffled until long trials and frustrations but finally I came to find out that complex number is dealing with voltage lead and lag in capacitors and inductors mainly.You should remember this teaching in electricty level of learning.In capacitors the current leads the voltage by 90 degree if its considered by it self.And in Inductors the current leads the voltage by 90 degrees if considered by it's self.But with a combination of resistors and reactances then the degrees become less then 90 degrees.Check out the allaboutcircuits E-book on complex numbers for futher instructions on how to use the equations. Good Luck :cool:
  5. raks_universe

    Thread Starter Active Member

    Mar 15, 2009
    What does the negative frequency denotes...??

    Pls explain the concept of negative frequency.....

    Fourier transform of unit impulse function(delta) function gives d.c(constant) value in frequency domain, what it is denoting...??....what it explains for the component at negative frequency region.....

    Pls explain the negative frequency with above example...