Specifies the FFT width of the device. The FFT width is the effective bandwidth of the signal path during each signal acquisition.

Syntax

RFMXINSTR_ATTR_FFT_WIDTH

Numeric Value

Data Type

Access

Applies To

22

float64

Read/Write

N/A

Remarks


The lower limit for all devices that support setting the FFT Width attribute is 7.325 kHz.

PXIe-5663/5663E: The FFT width upper limit for the PXIe-5663/5663E depends on the RF frequency and on the module revision of the PXIe-5601. For more information about determining which revision of the PXIe-5601 RF downconverter you have installed, refer to the Identifying Module Revision topic in the NI RF Vector Signal Analyzers Help.
Note

The maximum FFT width for your device is constrained to 50 MHz or 25 MHz, depending on the digitizer option you purchased.

Note

You can use the FFT Width attribute with in-band retuning. For more information about in-band retuning, refer to the RFMXINSTR_ATTR_DOWNCONVERTER_CENTER_FREQUENCY attribute.

The RFmx driver treats the device instantaneous bandwidth as the effective real-time bandwidth of the signal path. The span specifies the frequency range of the computed spectrum. A signal analyzer can acquire a bandwidth only within the device instantaneous bandwidth. If the span you choose is greater than the device instantaneous bandwidth, the RFmx driver obtains multiple acquisitions and combines them into a single spectrum. By specifying the FFT width, you can control the specific bandwidth obtained in each signal acquisition.

You do not need to use a selector string if you want to configure this attribute for all signal instances. Specify the signal name in the selector string if you want to configure or read that signal instance. Refer to the Selector String topic for information about the string syntax.

Supported devices: PXIe-5663/5663E/5665, PXIe-5668