First Fractional-N phase noise table

[robismyname]

ADISimmPLL provides a report summary page that list my total phase noise for a given frequency. See attachment. My question is how do I know if these are good values or great values or excellent values? What would be ideal total values for a fractional-N phase noise table? I am trying to find a way to determine how good my values are and can I improve them....... I'm up to chapter 5 of deans book and nothing helps yet.....

 

[Mazz]

Good or bad depends on your specification. If you don't have a target spec to satisfy, how will you know if noise is too much or not?

Anyway, which freq are you targetting?

Mazz

 

[robismyname]

Anyway, which freq are you targetting?

Mazz

Not sure what you mean but this is what I know. I hope it helps you so that you can help me.

This ADISimmPLL design is in reference to the first IF stage. The stage where the channel selection and tuning occurs. I am in the ISM band 2.4GHz - 2.483Ghz. My channel spacing is 1MHz. My VCO has a range of 2100MHz-2500MHz. My IF is 140MHz............

 

[Mazz]

From your explanation I think I can resume some infos:

-your design is a receiver, probably a supehet one. Right?

-The PLL is used as local oscillator for first downconversion mixer, right?

-You are working in thr ISM 2.4 GHz BW (bluetooth aaplication?). So, if you need to receive, for example, 2440MHz, your PLL will synthesize 2440-140=2300MHz, right?

Just arguing...

Mazz

 

[robismyname]

From your explanation I think I can resume some infos:

-your design is a receiver, probably a supehet one. Right? Mazz

yes, dual conversion.

-The PLL is used as local oscillator for first downconversion mixer, right?
Mazz

I am using a dual fractional N PLL.

-You are working in thr ISM 2.4 GHz BW (bluetooth aaplication?). So, if you need to receive, for example, 2440MHz, your PLL will synthesize 2440-140=2300MHz, right?
Mazz

I am using the ISM spectrum but its not bluetooth because I am not frequency hopping. Im using FSK. Your assumptions are correct about the synthesizer.

Now please help with the phase noise table issue I posted originally......

 

[Mazz]

Yes I would like to help you.
But what really is your issue? Do you have an idea about the reason to make a clean LO?

I can only say that, your phase noise seems very good for a superhet application.

If you need to understand better all the issues related to RF subsystem design, let me suggest the excellent book of Qizheng Gu.

Mazz

 

[jecyhale]

ADISimmPLL provides a report summary page that list my total phase noise for a given frequency. See attachment. My question is how do I know if these are good values or great values or excellent values? What would be ideal total values for a fractional-N phase noise table? I am trying to find a way to determine how good my values are and can I improve them....... I'm up to chapter 5 of deans book and nothing helps yet.....

It is good or bad detemined by the system.

So you should use it in some system, then to find whether its performance is ok.

Besides, phase noise is not all which should be cared.

 

[robismyname]

Yes I would like to help you.
But what really is your issue? Mazz

Please look at my original post. My questions are:

1) how do I know if these are good values or great values or excellent values?

2) What would be ideal total values for a fractional-N phase noise table?

reason for question #1 and #2 is because I am trying to find a way to determine how good my values are and can I improve them

I can only say that, your phase noise seems very good for a superhet application.
Mazz

Can you just tell me why you feel that the phase noise seems OK? Is this a difficult question to answer?

 

[Mazz]

I think we are going around with a no-end discussion.

Phase noise (as any other parameter) is not absolutely good or bad. It limits certain performance of the receiver (for example the adjacent channel rejection).
I think you need to start from a specification of channels rejection, make all the calculations (taking into account SAW filter and so on) and derive a spec for the phase noise.
So you'll be able to understand if this is good or bad.

I hope it can help.

Mazz

 

[robismyname]

I think we are going around with a no-end discussion.
Mazz

Thanks for trying to help. I agree this is going no where.

I will end this by saying that you said phase noise seems very good but you never told me why you think its goods. Dont understand how can you tell me the phase noise seems very good but cant explain it in a line or two.

Thanks for trying I will inquire through other resources..........

 

[BigBoss]

Ask to your system designer who will define your PN requirements for this architecture.Because PN has no information by itself but it's meaningful with your additional system information such as (de)modulation type, bandwidth, coding, fading effects etc.
Therefore a system designer can answer to this question who can simulate the whole system with provided data..