Phase noise of fractional-N PLL

[sugar_luo2003]

Hi, All,

Who can tell me the the following specification is difficult or not, especially on the phase noise? Why? Thanks!!!

VCO Frequency: 50MHz - 1050MHz.
Frequency Step: About 30kHz.
Phase Noise: 90dBc/Hz at 1kHz offset.
Power supply: 3.3V.
Process: BiCMOS.

Sugar

 

[egemini]

Yes , it is possible.
You may need to switch vco to cover full range.
LMX2352 series frm National will do.
To obtain phase noise spec you may need to use hi Q inductors from coilcraft or use a coaxial resonator at high frequencies.

thanks

 

[hanjiemy]

yes, i agree.
what's the BW and LPF's order?

thks

 

[egemini]

There is an on line loop filter design software available on National web site Webench . Please check that **broken link removed**
thanks

 

[divan]

Yes , it is possible.
You may need to switch vco to cover full range.
To obtain phase noise spec you may need to use hi Q inductors from coilcraft or use a coaxial resonator at high frequencies.

HEllo egemini !
how do you offer to switch L or coax in the range 50-1050 ?
in my opinion . the only way is to use 2050 -3050MHZ VCO driven - 2000 MHz osc deadly locked. Isn't ?
BTW , to achive -90@1KHz for 2G-3G m.b. a problem , i don't remember any such good VCO .

 

[hanjiemy]

for low phase noise, i suggest u should use LC tank VCO.and u need choose hign Q inductor. BTW, the large swing @vcotank will help u. Of course, it need a trade-off. but I think u must know u'ld rather low phase noise than the others.

I hope it can help u.

 

[colombo2]

I doubt the LC tank will tune over such range.
Multiple VCOs maybe but here is an old trick from TV sysnthesizer. Raise the frequency from 50-1050 to something like 1050-2050 then downconvert with a fixed LO