Lock-in Amplifier

Moku's Lock-in Amplifier currently does not support phase unwrapping. While it can output phase as the error signal, the phase detector is limited to one cycle of dynamic range.

This limitation arises because the effective range of the arctangent function is [-π, π]. When X changes sign, the Y/X ratio shifts from approximately -∞ to +∞, causing the arctangent to produce an abrupt change. To resolve this issue, we would need to collect the phase output from the Lock-in Amplifier and perform an unwrap operation using MATLAB's unwrap function.

Phasemeter

Moku's Phasemeter has phase unwrapping capabilities. The Phasemeter uses a phase-locked loop to track the phase of the input signal by integrating the phase change applied to the internal oscillator. This method differs from that of the Lock-in Amplifier and is immune to the phase changes caused by the arctangent's effective range limitations.

Frequency Response Analyzer

Moku's Frequency Response Analyzer has phase unwrapping capabilities as well. Although it is similar to a Lock-in Amplifier, the Frequency Response Analyzer includes an integrated unwrap function, similar to that of MATLAB. However, this unwrapped phase can be inaccurate if the signal is obscured by the noise floor, as phase changes can be incorrectly recognized in this situation, leading to significant phase errors.