# Tag Info

### why need de-correlated signal for measuring phase noise in laser

Because you can't measure absolute phase -- you can only measure the phase difference between your unit under test and a reference. If you have a reference that's perfectly correlated to your unit ...
• 7,986

### why need de-correlated signal for measuring phase noise in laser

Let's look at one coefficient of the correlation $$c_l = \mathbb{E} \left[ x_k x_{k+l}^* e^{1j (\theta_k - \theta_l)}\right]$$ $$c_l = \mathbb{E} \left[ z_{k,l} e^{1j (\theta_k - \theta_l)}\right]$$ ...
• 1,463
Accepted

### understanding a spectrum of a modulated signal

The spectrum will be identical for all cases of oversampling. (The frequency axis just scales accordingly). Proper oversampling does not modify the spectrum in band in any way whatsoever, but on the ...
• 36k
1 vote

### Power of signal in specific frequency in FM and AM modulation

This is a common homework or quiz/test problem so I won’t bypass the learning experience by providing the full solution, but I will provide further details that will give intuitive insight into the ...
• 36k
1 vote
Accepted

### A scaling difference between MATLAB's pwelch and Python's SciPy welch

MATLAB's function pwelch scales the PSD under the assumption that the DFT is executed across the range of $0:2 \pi$ in the event the sample frequency is not passed to the function. Thus, you have ...
• 26