integer n frequency synthesizer
eg. for codeless phone and wlan 802.11a
thanks.
Yes. Because this design method can produce ralative lower phase noise.
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.
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.
suggest sigma delta fraction N PLL.
So where does a DDS fit into the picture?
When do you use a DDS for synthesis rather than fractional-N plls?
When you can afford to have a noisy synthesizer...
if lock-in time is important fractional-N is faster.
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.
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.
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?