**Sarig wrote on Dec 8**^{th}, 2007, 2:09am:1. "Phases" has no frequency components in it. Its the accumulated phase which is the Phase jitter of my VCO, so I don't understand what is the meaning of PSD on "phases" (can you explain?)

2. My data is at 5GHz frequency and in order to bring it to Matlab for lets say 1mS (I want Phase noise from 1kHz - 1MHz) I will need enormous excel file.

3. Can I take my VCO output, pass it via Mixer, filter the output at lets say 0.5GHz and do PSD on the result?

It is known that because the signal is sin and the noise is very low the total noise will be the phase noise so simply do PSD (Please comment)

Regards,

Erez

Hi Erez,

1. "phases" is a vector of accumulated phase jitter (in radian), for 1st, 2nd, 3rd, 4th, .. n-th cycle. Look up "psd" in your favourite post-processing tool. This function divides your data into multiple segments of "nfft" data points each, do a FFT on each segment, and average the power. The result is a periodogram estimate of the power spectral density in unit of radian^2/Hz.

2. I would be more concerned with your simulator accuracy and your run time. One reason I suggest making a periods vs time measurement is to trim down the raw data size to ease data exporting/importing.

3. Some phase noise measurement instructments use this method. I call this the Mixer method, and this too works fine on several frac-N and int-N PLLs that I compared with lab measurement.