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ice:servo-opls [2019/11/18 23:29] – [Table] Michael Radunsky | ice:servo-opls [2019/11/18 23:33] – [Understanding the Transfer Function] Michael Radunsky |
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The charge pump in the OPLS outputs a signal proportional to the phase-error and the transfer function is as shown in <imgref xferfunc>. However, the OPLS will typically be used to control a //frequency//-tunable device (such as a laser). In this configuration, the effective loop filter is not the one shown in <imgref opls_side_panel>, but includes a extra integration corresponding to converting the phase-error input to a frequency error. Thus, ω<sub>I </sub>sets the frequency transition from single-integration to double-integration and ω<sub>I </sub> from single-integration to proportional feedback. It is important to understand this 'hidden' integrator when configuring the loop filter parameters. | The charge pump in the OPLS outputs a signal proportional to the phase-error and the transfer function is as shown in <imgref xferfunc>. However, the OPLS will typically be used to control a //frequency//-tunable device (such as a laser). In this configuration, the effective loop filter is not the one shown in <imgref xferfunc>, but includes a extra integration corresponding to converting the phase-error input to a frequency error. Thus, ω<sub>I </sub>sets the frequency transition from single-integration to double-integration and ω<sub>I </sub> from single-integration to proportional feedback. It is important to understand this 'hidden' integrator when configuring the loop filter parameters. |
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=====Calculating Phase Noise ===== | =====Calculating Phase Noise ===== |
The phase-noise specified in Section 1.3 is referenced to the phase frequency detector (PFD) at 1 Hz. To convert that to the noise measured on the actual beat-note, it must be rescaled with the following formula: | The phase-noise specified in Section 1.3 is referenced to the phase frequency detector (PFD) at 1 Hz. To convert that to the noise measured on the actual beat-note, it must be rescaled with the following formula: |
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<WRAP center round box 450px><html><center></html> **D2-135 Phase-Noise Floor = -213 + 20Log(N) + 10Log(F<sub>REF</sub>)**<html></center></html></WRAP> | <WRAP center round box 450px> **D2-135 Phase-Noise Floor = -213 + 20Log(N) + 10Log(ƒ<sub>REF</sub>)**</WRAP> |
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where N is the value of the divider and F<sub>REF</sub> is the reference frequency as measured in Hz. For more details, please see this [[http://www.vescent.com/2012/calculating-phase-noise-from-the-d2-135/|application note]]. | where N is the value of the divider and ƒ<sub>REF</sub> is the reference frequency as measured in Hz. For more details, please see this [[http://www.vescent.com/2012/calculating-phase-noise-from-the-d2-135/|application note]]. |
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