Difference between revisions of "NVGate time shift resampling"

Time Shift Resampling with OROS Analyzer and NVGate software

This document intends to highlight internal signal processing of OR3x with regards to phase precision of Time trigger blocks in NVGate. When trigger event occurs in between two samples of acquisition error may be introduced in absolute phase measurement of the acquired Time block (see Picture 1). Enhanced signal processing of NVGate enables to minimize this error by finding start of trigger even with a much higher precision and performing time shift resampling.

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OR3x Front end features 2 External Sync inputs (2 logic inputs) that have integrated pre-divider enabling oversampling of external trigger channel. For instance when Input Front End Sampling is set to 102.4kS/s (40 kHz bandwidth) External Sync 1 and 2 have detection precision equivalent to 6.5MHz (#102.4*64). Trigger event resolution therefore increases from 9.7 micro seconds (sample rate @ 102.4 kS/s) to 151 nano seconds.

Enhanced signal processing of OR3x enable phase improvement of trigger block by time resampling of acquired trigger block (at sampling frequency) with a resolution of 1/16^th of a sample. This is made according to the External Sync precise start event. (See Picture 2)

[[Image:Time_shift_resampling_02.png|framed|none]]

Signal processing for time shift resampling is automatically engaged when "Time" averaging is selected in NVGate FFT plug in (see Picture 3).

[[Image:Time_shift_resampling_03.png|framed|none]]

Standard absolute phase error calculation without time shift resampling can be determined as follow (worst case where event occurs right after last sample)

for instance for a total analysis band of 20kHz, maximum error at 10kHz frequency will be Phase_error = (360/2.56)*10/20 = 70.3 deg

Standard absolute phase error calculation with Time Shift Resampling can be determined as follow (worst case where event occurs right after 1/16^th of a sample )