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Transfer Function

A transfer function is a total measurement of the amplitude and phase response of a device under test

A key part of an accurate transfer function is the removal of the input test signal response from the final measurement.  This is done by passing a sample of the input signal to the second channel of the analyzer and removing its response from the response of the device under test. 

You should use logarithmic amplitude scaling; subtracting two logarithmic quantities equates to division of their ratio values.

Procedure:
  • Connect a noise generator to the input of the device under test.
  • Connect the output of the device under test to one input channel of the analyzer.
  • Connect same signal generator to a different input channel of the analyzer.
  • Setup a Composite Channel to produce the transfer function between the two channels
  • Run the analyzer until the average spectrum response settles to a consistent level.

    Interpretation:
    The spectrum display contains the amplitude response of the device and the phase display contains the phase response.