LIGO Document T080119-v2

Simple Calculation of Active Platform Performance

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T - Technical notes
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We derive the performance equations for an active isolation system. We consider ground translation, ground tilt, and sensor noise for a system with sensor blending and sensor correction. We assume a plant and sensor with no cross coupling, except for low-frequency tilt-horizontal coupling. We see that, at low frequency, the transmission of ground translation is approximately equal to the displacement sensor blending filter, for systems with feedback only. When sensor correction is added, the low-frequency performance becomes the product of the displacement sensor blend filter and the complement of the high-pass sensor correction signal.
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HAM ISI Model Platform Noise

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