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BSA Flow Software Installation and User's Guide - CSI

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Scope: Burst spectrum display<br />

Record Interval The record interval is indicated by the vertical dotted<br />

lines (Figure 5-15), except for <strong>BSA</strong> F/P 30 processor where no record<br />

interval is displaid. For auto-adaptive record length mode (see section 0), the<br />

minimum <strong>and</strong> maximum record intervals are indicated (Figure 5-16). In<br />

Normal user interface mode, the record length is set to autoadaptive mode.<br />

Ideally, the record interval should match the duration of the shortest bursts,<br />

but the processor is robust to deviations from the ideal case. The record<br />

interval depends on the record length <strong>and</strong> the velocity span properties of the<br />

channel, see section 0.<br />

If the burst is shorter than the record interval, a part of the record is from<br />

outside the burst. If the signal-to-noise ratio is high, this hardly influences<br />

the estimation of the frequency. However, the shorter the burst is, the less<br />

accurate the frequency estimation becomes. Bursts shorter than the record<br />

interval are only seen at very high velocities, so for most applications there<br />

is no problem.<br />

If the burst is longer than the record length, only the part within the record<br />

interval is used for the frequency estimation. The spectrum of a burst which<br />

is cut off at both ends will have some side peaks, but since we are only<br />

estimating the main peak, the effect of cutting off is small.<br />

Figure 5-15 System Monitor,<br />

Scope display set to Burst Signal<br />

Auto-adaptive mode (Normal<br />

user interface)<br />

Figure 5-16 System Monitor,<br />

Scope display set to Burst<br />

Spectrum Fixed record (Advanced<br />

user interface)<br />

The Burst spectrum display, Figure 5-17, shows the power spectrum of the<br />

signal seen by the processor. The X-axis scaling corresponds to the chosen<br />

Center velocity <strong>and</strong> Velocity span settings.<br />

This display can help to localise the main spectral peak of the signal, so that<br />

the Center velocity <strong>and</strong> Velocity span settings can be optimised.<br />

The Burst spectrum display is available from the Scope display in the<br />

group properties.<br />

<strong>BSA</strong> <strong>Flow</strong> <strong>Software</strong>: Project explorer objects 5-23

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