Marios
Junior Member
![* *](https://designers-guide.org/forum/Templates/Forum/default/starblue.gif)
Offline
Posts: 15
|
Ok thanks for your time. I have 2 more questions and everyone's answer would be much appreciated.
1) Assuming a traditional CMOS implementation of the PDF and noiseless power rails, noise is injected only during the transitions of the UP & DN pulses. This noise arrives at the output as "packets" and the total output noise is a function of the oscillation period and the noise packet duration ~(t_noise_duration/period_fundamental). For that reason doubling the frequency will theoretically increase thermal noise levels by 3dB and flicker by 6dB (as fundamental period becomes half while noise injection duration remains constant). However, if I use double the frequency, flicker does indeed increase by 6dB while thermal remains the same! I would say that thermal is dominated by a non-periodic noise thus does not scale with frequency but I cannot seem to understand where does this noise come from. It flats out at -170dBv/Hz.
2) If I enclose the PFD within a very wideband PLL without feedback divider, measuring output phase noise should yield the same results as the ones measuring using the method described previously right?
Marios
|