Acquisition:Spectrum:Span Property

Acquisition:Spectrum:Span Property

Short Name: Span

Property of niRFSA

Specifies the frequency range of the computed spectrum in Hz. 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 FFT Width property to improve amplitude accuracy and avoid unwanted effects such as filter rolloff 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 devices, NI-RFSA enables dithering by default. The dither noise can appear in your passband and affect measurements. Refer to the Digitizer Dither Enabled property 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, 20 MHz and 10 MHz respectively.

PXIe-5665 (14 GHz)/5667 (7 GHz)/5668—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

Remarks

The following table lists the characteristics of this property.

Datatype
Permissions	Read/Write
High-level VIs	niRFSA Configure Spectrum Frequency
Channel-based	No
Resettable	Yes