| 11. | This results in a 100 kHz difference frequency proportional in level to the bridge unbalance.
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| 12. | Parametric sources use the non-linearity of water to generate the difference frequency between two high frequencies.
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| 13. | The difference frequency signal is amplified by a filter amplifier combination and is applied to a null meter.
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| 14. | This beat signal, detectable with a photodiode, includes a difference frequency component, which is the carrier envelope offset frequency.
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| 15. | Hence, narrow electronic filtering near the difference frequency is highly effective at removing the remaining, generally broadband, noise sources.
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| 16. | Also, the animation contains both up-and down-converted spectra, which is due to a frequency mixer producing both sum and difference frequencies.
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| 17. | In contrast, the harmonic and subharmonic mixers form sum and difference frequencies at a harmonic multiple of one of the inputs.
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| 18. | A heterodyne bat detector combines the bat call with a constant internal frequency so that sum and difference frequencies are generated.
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| 19. | A simple mixer will pass both of the input frequencies and all of their harmonics along with the sum and difference frequencies.
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| 20. | An alternative to stabilizing the carrier envelope offset frequency is to cancel it completely by use of difference frequency generation ( DFG ).
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