Specifies the frequency range of the computed spectrum in hertz (Hz).

Syntax

NIRFSA_ATTR_SPECTRUM_SPAN

Numeric Value

Data Type

Access

Applies To

1150003

ViReal64

Read/Write

N/A

Remarks


For example, if you specify a center frequency of 1 GHz and a span of 100 MHz, the spectrum ranges from 950 MHz to 1,050 MHz after zoom processing. This value may be coerced based on hardware settings and RF downconverter specifications.

NI-RFSA performs multispan acquisitions by dividing the total requested span into equally sized subspans based on the device instantaneous bandwidth at the range of frequencies you specify. NI-RFSA combines these subspans to yield a multispan acquisition. You can use the NIRFSA_ATTR_FFT_WIDTH attribute to improve amplitude accuracy and avoid unwanted effects such as filter roll-off and spurs across the span you select.

Note

If you configure the spectrum span to a value larger than the hardware instantaneous bandwidth, NI-RFSA performs multiple acquisitions and combines them into a spectrum of the size you requested.

Note

For the PXIe-5663/5663E/5665/5667/5668, NI-RFSA enables dithering by default. The dither noise can appear in your passband and affect measurements. Refer to the NIRFSA_ATTR_DIGITIZER_DITHER_ENABLED attribute for more information about dithering.

PXIe-5663/5663E: NI-RFSA does not support multispan acquisitions from frequency ranges that correspond with different instantaneous bandwidths. For example, you cannot configure a multispan acquisition that acquires one span from 110 MHz to 120 MHz and a second from 120 MHz to 130 MHz because the instantaneous bandwidth for frequencies above 120 MHz is different than instantaneous bandwidth for frequencies less than 120 MHz, which are 20 MHz and 10 MHz respectively.

PXIe-5665 (14 GHz)/5667 (7 GHz): If you enable the downconverter preselector filter, the device instantaneous bandwidth is only a typical specification.

Default Value: 10 MHz

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5840/5841/5842/5860

High-Level Functions: