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elektr0
Joined: 02 May 2006
Posts: 171
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 22 Jul 2008 20:57 AMPLIFIER - third harmonic output |
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Hello,
there should be a direct relationship between the input power, the power within the third harmonic of an amplifer and its INPUT or OUTPUT IP3.
Does anybody have a formula ?
What would you say ? How less input power is valid if 40 or 50dBc to the third harmonic is needed.
10dB less than the 1dB compression point.
Which input power is sufficient for 40dB spur free dynamic range when using RF-mixers ?
Thanks
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vfone
Joined: 10 Oct 2001
Posts: 1716
Helped: 223
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| 22 Jul 2008 22:40 Re: AMPLIFIER - third harmonic output |
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The 3rd harmonic depends by input power, but the level is not predictable in a nonlinear device.
The level of the harmonics vs input power depends by the power class of the amplifier.
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RF-OM
Joined: 03 Aug 2007
Posts: 607
Helped: 113
Location: The Earth
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| 23 Jul 2008 3:51 Re: AMPLIFIER - third harmonic output |
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The level for third harmonic does not directly related to the IP3 because not only third order distortion contributes to the third order harmonic level. Other orders distortion processes also contribute to the third level harmonic. It practically depends on circuit and its parts non-linearity as well as bandwidth. The best way to determine it is to use measurements.
Input power corresponding to certain SFDR level can be determined from well known equation Pin=SFDR+MDS.
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Abhishekabs
Joined: 12 Jan 2007
Posts: 478
Helped: 58
Location: India
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| 23 Jul 2008 7:20 AMPLIFIER - third harmonic output |
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You get harmonics because of nonlinearity.
So there is no direct relation.
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