Why does pwelch function use a hamming window as default while periodogram function use a rectangular window?

Is the algorithm of the "pwelch" function the same with the algorithm of the "periodogram" function? Why do they use different default window? In the "periodogram" function, the result is scaled with 2*pi*N. But it seems that in the "pwelch" function, the result is scaled with pi*N. Where can I get the algorithm of the "pwelch" function? If I change the hamming window to a rectangular window in "pwelch" function, why is the estimate spectrum not accurate when the digital frequency is close to pi?

Answer 1

[the cyclist]

I don't have the Signal Processing Toolbox, so I can't help much. But here are two tips:

1. Take a look at the documentation. There are often references there that related to the algorithms chosen.
2. Take a look at the details of the function itself by typing "edit pwelch" at the command line.