A frequency response analyzer includes a signal generator, a reference channel module, and a digital frequency response analyzer. The signal generator includes an input, a first output to provide an output signal to a unit under test, and a second output to provide a first synchronization signal. The reference channel module includes an input coupled to the first output of the signal generator, and an output to provide phase information data of the output signal. The digital frequency response analyzer includes a first input to receive the first synchronization signal, and a second input to receive digitized analog data from the unit under test. A processor of the frequency response analyzer correlates received digitized analog data to received analog data based on the phase, and determines a transfer function of the plant of the unit under test based on the correlation of received digitized analog data and received analog data.