PM Demodulation

PM demodulation is computed as an arc tangent of the complex time record.

For PM demodulation, Auto Carrier Frequency and Auto Carrier Phase determine how the VSA handles frequency and phase errors between your carrier frequency and the VSA's center frequency.

Selecting Auto Carrier Phase subtracts the mean phase across the time record, moving the mean phase to zero. No frequency estimation is performed. Thus, this type of auto carrier is useful when the measurement hardware is locked to an external reference which is coherent with your carrier.

Selecting Auto Carrier Frequency performs carrier frequency estimation, as well as moving the mean phase to zero. To display the estimated carrier frequency, turn on Analog Demod Carrier.

The following illustration shows how the VSA detects the carrier phase and frequency.

$image\PM_blk_wmf.jpg$

The following illustration is an example of a carrier PM modulated by a sine wave.

$image\PMwaveform_wmf.jpg$