hi, i'm simulating PLL phase noise contribution from CP. when i use PLL+Pnoise to simulate the CP/PFD noise current output, i see a huge spike at comparison frequency.

how this spike generated? is there any relationship to reference spur (or i should ask: can i use this spike to simulate reference spur)

thanks

hi, peter,

thanks for reply. I fully agree with the cause of reference spur.

In fact, my concern is:

1. as u say, the reference spur is caused by mismatach/leakage CURRENT, in stead of CURRENT NOISE ; but the spike i see is in Pnoise result (i check the current noise); do u think these 2 are in fact same thing?

2. i normally use CP current noise (simulate with PSS+Pnoise) to calculate pn due to CP, i have compared simulation to measurement, they're reasonablely close; but i never check current noise at comparison frequency until recently I happen to see this spike.

mathmatically, this spike is due to convolution of huge flicker noise value at 0-frequency with square wave; but physically, what it mean?

thanks