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How to Calculate Group Delay

Radio signals are examples of modulated transmission. An audio signal gets put on top of a carrier wave, so the carrier wave is modified by the transmitter, then the modifications are sensed at the receiver. Same thing for your cellphone, television and your Internet signal. Each signal has to go through preamplifiers, amplifiers and various filters. Each stage can change the form of the signal ̵2; that is, distort it. Group delay is a way to measure that distortion.

Things You'll Need

  • Filter circuit
  • Electronic signal
  • Spectrum analyzer
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Instructions

    • 1

      Measure or simulate the phase response of the filter circuit. For electronic circuits, this is often done with a simulation program such as PSPICE. For example, your filter might have a phase delay of 0.12 radians per hertz (cycles per second) at 250 hertz and 0.09 radians per hertz at 4,000 hertz.

    • 2

      Measure the frequency range contained in your signal. Put the signal into the spectrum analyzer and identify the frequencies. For example, your signal might contain a frequency range from 250 hertz to 4,000 hertz.

    • 3

      Calculate the group delay across the frequency range. The group delay in seconds is given by the phase delay in radians divided by 2 pi. For the example, the delay at 250 hertz is given by 0.12/(2 x pi), which is 0.019 seconds, while the delay at 4,000 hertz is 0.015 seconds.


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