| Author |
Message |
sugar_luo2003
Joined: 24 Jun 2004
Posts: 8
|
 28 Jun 2004 5:24 Phase noise of fractional-N PLL |
|
|
|
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
|
|
| Back to top |
|
 |
egemini
Joined: 02 Apr 2002
Posts: 157
Helped: 2
Location: GOC
|
| 28 Jun 2004 6:09 Re: Phase noise of fractional-N PLL |
|
|
|
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
|
|
| Back to top |
|
|
hanjiemy
Joined: 11 Jun 2004
Posts: 54
|
| 01 Jul 2004 4:52 Phase noise of fractional-N PLL |
|
|
|
yes, i agree.
what's the BW and LPF's order?
thks
|
|
| Back to top |
|
|
egemini
Joined: 02 Apr 2002
Posts: 157
Helped: 2
Location: GOC
|
| 01 Jul 2004 6:45 Re: Phase noise of fractional-N PLL |
|
|
|
There is an on line loop filter design software available on National web site Webench   . Please check that http://www.national.com/appinfo/wireless/webench/
thanks
|
|
| Back to top |
|
|
divan
Joined: 01 Mar 2002
Posts: 90
Helped: 2
|
| 01 Jul 2004 10:55 Re: Phase noise of fractional-N PLL |
|
|
|
| egemini wrote: |
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(at)1KHz for 2G-3G m.b. a problem , i don't remember any such good VCO .
|
|
| Back to top |
|
|
hanjiemy
Joined: 11 Jun 2004
Posts: 54
|
| 02 Jul 2004 8:46 Phase noise of fractional-N PLL |
|
|
|
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.
|
|
| Back to top |
|
|
colombo2
Joined: 02 Dec 2003
Posts: 35
|
| 06 Jul 2004 6:26 Re: Phase noise of fractional-N PLL |
|
|
|
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
|
|
| Back to top |
|
|
