Chapter 2
NI 5450 Overview
NI PXIe-5450 User Manual
2-22
ni.com
I/Q Rate
The I/Q rate component holds off the data from the output engine so that a
new sample is only returned once every Total_OSP_Interpolation Sample
clocks.
Note
The Total_OSP_Interpolation is the amount of interpolation applied within the
Filtering and Interpolation component, and does not include the DAC interpolation.
Prefilter Gain
Prefilter gain can change the gain of the I and Q stream during signal
generation. You can change the I and Q prefilter gains independently by
setting the Pre-Filter Gain I and Pre-Filter Gain Q properties or the
NIFGEN_ATTR_OSP_PRE_FILTER_GAIN_I
and
NIFGEN_ATTR_OSP_PRE_FILTER_GAIN_Q
attributes. The gain can range
from
–
16.0 to +16.0 (unitless). Any time the prefilter gain changes, the
OSP block ignores all overflows for the next I/Q samples. If an overflow
occurs during these samples, the data is clipped but an error is not returned.
The prefilter gain can be used to attenuate the I/Q data to eliminate
overflows in later stages of the OSP block.
Prefilter Gain Overflow
Any time the following condition is not true for the I or Q data stream, an
overflow occurs when prefilter gain is applied:
–
1
≤
User Data × Prefilter Gain
≤
1
If an overflow occurs, the data is clipped and NI-FGEN returns an error. To
prevent data clipping, attenuate the waveform data or reduce the prefilter
gain.
Tip
To disable error reporting caused by OSP overflows, use the OSP Overflow Error
Reporting property or the
NIFGEN_ATTR_OSP_OVERFLOW_ERROR_REPORTING
attribute.
Prefilter Offset
Prefilter offset can add offset to the I and Q stream during signal
generation. Change the I and Q prefilter offsets independently by setting
the Pre-Filter Offset I and Pre-Filter Offset Q properties or the
NIFGEN_ATTR_OSP_PRE_FILTER_OFFSET_I
and
NIFGEN_ATTR_OSP_PRE_FILTER_OFFSET_Q
attributes. The offset can
