fractional-N vs integer-N frequency synthesizer?

[RC13]

integer n frequency synthesizer

is it fractional-N frequency synthesizer good for narrow-band system while integer-N good for wide-band system?

eg. for codeless phone and wlan 802.11a

thanks.

 

[cybq]

integer vs fractional synthesizer

Yes. Because this design method can produce ralative lower phase noise.

 

[toonafishy]

fractional vs integer-n synthesizers

Fractional-N will always give better phase noise performance since you will be using a lower value of N compared to an integer synthesizer. The tradeoff is that the fractional N synthesizer is more complex and you also have fractional reference spurs to deal with instead of just the integer reference spurs. But for phase noise and switching speed, fractional is the way to go.

 

[md]

integer vs fractional vco

also for the integer-n, your frequency step size is limited with your crystal oscillator frequency, you can only generate integer multiples of the input frequency.

 

[IICCEE]

dds vs fractional-n

suggest sigma delta fraction N PLL.

 

[twinsen]

fractional-n and integer-n synthesis

So where does a DDS fit into the picture?

When do you use a DDS for synthesis rather than fractional-N plls?

 

[toonafishy]

space fractional-n synthesizer -sige

When you can afford to have a noisy synthesizer...

 

[aaiiwwaa]

what is a fractional synthesizer

if lock-in time is important fractional-N is faster.

 

[RC13]

fractional vs integer

any sw can simulate the fractional-n frequency synthesizer at about 2.0/4.0Ghz VCO output, and input reference fequency of about 5MHz?

the fractional-n involve digital block (accumulator/phase detector), analog block (charge pump/loop filter), and rf block (VCO), and high frequency digital block( prescaler). hence, it is really tough to simulate it.

i have use /h/s/i/m/ for low frequency PLL, it is really fast and the result is quite close to the measured, but i don't know it can be used for 2.0/4.0Ghz design.

 

[nozone]

n-frequency synthesizer

I have tried to simulated it. there is a F-N sample for this, one even with sigma-delta modulation, although it's not the optimum choice.

 

[kjjian]

wideband dds frequency synthesizer

Now my team is go on a project about 802.15.4 based on 2.4G band. The channel space is 5M. Is Integer-N good or Fractional-N good?
if the Fractional-N is good,how can i decide the reference frequency?

Added after 22 seconds:

Now my team is going on a project about 802.15.4 based on 2.4G band. The channel space is 5M. Is Integer-N good or Fractional-N good?
if the Fractional-N is good,how can i decide the reference frequency?