Complex Cluster

Fetches I/Q data from a single record in an acquisition.

Inputs/Outputs

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session in

Instrument session obtained from Initialize With Options.

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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Default value: No error

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samples to read

Number of samples to fetch.

A value of -1 specifies that NI-RFSA fetches all samples.

Note If you set this input to -1, NI-RFSA fetches all remaining samples currently available depending on your settings for the Fetch Relative To property and the Fetch Offset property.

Default value: -1

Number of Samples Not Available

If the number of samples specified in this input is not available after the time duration specified in the timeout input, Fetch IQ returns no data with a timeout error.

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timeout

Time, in seconds, allotted for the node to complete before returning a timeout error. For the PXIe-5644/5645/5646, PXIe-5668, and the PXIe-5820/5840, this input specifies the time allotted to receive the reference trigger.

Default value: 10

Timeout Value Behaviors

A value of -1 specifies that the node waits until all data is available. A value of 0 specifies that the node immediately returns available data.

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record to fetch

Record to retrieve.

Record numbers are zero-based.

Default value: 0

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session out

Reference to your instrument session passed to the next node.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

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data

Cluster of the acquired data.

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t0

Start time of the first sample returned.

The timestamp corresponds to the difference in seconds between the first sample returned and the Reference Trigger location.

Note The value of t0 returned in the data output is always 0 for the PXIe-5644/5645/5646.
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dt

Time interval between data points in the acquired signal.

The I/Q data sample rate is the reciprocal of this value.

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Y

Complex-value time domain data array.

The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.

Note The size of the array can vary per record if the Number of Samples property changes per step during RF list mode.

Calculating Instantaneous Power of a Sampled I/Q Point

To calculate the instantaneous power of a sampled I/Q point, use the equation (I2 + Q2)/2R, where R is the input impedance in ohms (Ω). For vector signal analyzers, R=50 Ω.

Hardware Support

This node supports the following hardware:

  • PXIe-5644/5645/5646
  • PXIe-5663E/5665/5667/5668
  • PXIe-5820/5840