Specifies the method for performing the ACP measurement.

You do not need to use a selector string to configure or read this property for the default signal instance. Refer to the Selector Strings topic for information about the string syntax for named signals.

The default value is Normal.

Remarks

The following table lists the characteristics of this property.

Short Name ACP Meas Method
Data type ci32.png
Permissions Read/Write
High-level VIs RFmxSpecAn ACP Configure Measurement Method
Resettable Yes
Normal 0

The ACP measurement acquires the spectrum using the same signal analyzer setting across frequency bands. Use this method when measurement speed is desirable over higher dynamic range.

Dynamic Range 1

The ACP measurement acquires the spectrum using the hardware-specific optimizations for different frequency bands. Use this method to get the best dynamic range.

Supported devices: PXIe-5665/5668
Sequential FFT 2

The ACP measurement acquires I/Q samples for a duration specified by the ACP Sweep Time property. These samples are divided into smaller chunks. The size of each chunk is defined by the ACP Sequential FFT Size property. The overlap between the chunks is defined by the ACP FFT Overlap Mode property. FFT is computed on each of these chunks. The resultant FFTs are averaged to get the spectrum and is used to compute ACP.

Sequential FFT method should be used for the following scenarios.

  1. While performing fast ACP measurements by utilizing smaller FFT sizes. However, accuracy of the results may be reduced.
  2. When measuring signals with time-varying spectral characteristics, sequential FFT with overlap mode set to Automatic should be used.
  3. For accurate power measurements when the power characteristics of the signal vary over time, averaging is allowed.

The following properties have limited support when you set the ACP Measurement Method property to Sequential FFT.

Property Supported Value
ACP RBW Auto True
ACP RBW Filter Type FFT Based
ACP Sweep Time Auto False
ACP Averaging Count >=1
ACP Num Analysis Threads 1
ACP Amplitude Correction Type RF Center Frequency
ACP Offset Rel Attn 0
Note For multi-span FFT, the averaging count should be 1.