What's PLL noise bandwidth? What's the relationship of noise bandwidth to loop bandwidth?
Can we minimaze PLL integrated phase noise by reduce PLL noise bandwidth?
the bandwidth of the PLL is the PLL noise bandwidth
but every noise source in the PLL has it's transfer function
so if you r talking about phase noise of the Xtal reffernce the noise transfer funcation is low pass filter so to minimize the the noise , decresae tha bandwidth
but the noise in VCO the transfer funcation is high pass filter to to minimize the VCO noise increase the bandwidth
I can't agree with you that the bandwidth of the PLL is the PLL noise bandwidth.
The PLL bandwidth is defined as the cross frequency at gain=1 of open loop. But noise bandwith is defined as following:
i think it wioll depend what is ur defintion of the bandwidth closed loop or open loop , when i am talking about PLL bandwidth i consider the pll is closed loop in lock state
This paper gives a clear relation between PLL bandwidth and jitter (assuming noise sources in each block causes jitter)
Original question : Can we minimaze PLL integrated phase noise by reduce PLL noise bandwidth?
The answer to this original question can be found in the paper. If noise from input clock source is dominant, then reducing the PLL (noise) bandwdith reduces the integrated phase noise at the output. But, if the VCO noise is dominant, then you need to have a high bandwidth to reduce the output integrated phase noise. Refer to the paper for an in-depth analysis.
What's PLL noise bandwidth? What's the relationship of noise bandwidth to loop bandwidth?
Can we minimaze PLL integrated phase noise by reduce PLL noise bandwidth?
Noise bandwidth depend on PLL bandwidth and noise characteriscs.
Integrating noise power density function in the whole PLL bandwidth and dividing it with dc noise value leads to noise bandwidth. For white noise, it has uniform value in its bandwidth. So for white noise PLL's noise bandwidth is equal to PLL's bandwidth.
PLL has two main noise source: input clock jitter and VCO noise. We can reduce PLL bandwidth to supress the former but have to enlarge the bandwidth to reduce the latter. There is a trade-off.