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AdvaRes
Joined: 14 Feb 2008
Posts: 1038
Helped: 46
Location: At home
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 17 Apr 2008 9:02 VCO tuning range |
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Hi members,
I noticed that always the VCO tuning range is between 40 and 80 % of the nominal voltage.
What about VCOs in which the Tuning range is between 80 % and 90 % ?
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khouly
Joined: 20 Oct 2003
Posts: 2479
Helped: 343
Location: EGYPT
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17 Apr 2008 9:15 VCO tuning range |
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the tuning range of the VCO depends on the CV curve of the varactor , so to get high tuning range u need the vacattor to have wide tuning volateg
khouly
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icsoul
Joined: 28 Nov 2005
Posts: 72
Helped: 3
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18 Apr 2008 13:38 Re: VCO tuning range |
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| You could do this with the control voltage of VCO in the related range.
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jecyhale
Joined: 19 Feb 2008
Posts: 447
Helped: 47
Location: China
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21 Apr 2008 4:54 Re: VCO tuning range |
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| AdvaRes wrote: |
Hi members,
I noticed that always the VCO tuning range is between 40 and 80 % of the nominal voltage.
What about VCOs in which the Tuning range is between 80 % and 90 % ? |
It is up to the CP output voltage range.
When the Vtune larger than 80% or lower than 20%, CP will be mismatch.
But if you use ADPLL, there is no problem.
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rfsystem
Joined: 25 Feb 2002
Posts: 858
Helped: 96
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22 Apr 2008 9:30 Re: VCO tuning range |
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| If the VCO could use only 10% of the supply as voltage tuning range it will be more sensitive to noise and tolerances. Typical designs try to maximize the range ro 20-80% which could be covered by either a chargepump or an opamp in an active loop filter.
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n1cm0c
Joined: 05 Sep 2006
Posts: 183
Helped: 25
Location: Santa Maria
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22 Apr 2008 10:37 Re: VCO tuning range |
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As mentioned, if VCO tuning range is covered by 10% of supply then Kvco is very high, making it very sensitive to noise in the tuning voltage.
One designs for a tuning voltage between 20% to 80% of supply rail because that's about the max useful output range of the CP.
This way one can lower the Kvco and reduce sensitivity to noise in the tuning control line.
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rosaeidi
Joined: 19 Dec 2006
Posts: 103
Helped: 6
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26 Apr 2008 6:42 VCO tuning range |
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Hi
Tuning range is depended on varactor network. You can have a tuning range from 2% to 100%.
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