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NI RFSA Acquisition Attributes

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Greg Stoll edited this page Nov 11, 2021 · 1 revision

Acquisition Attributes

NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W N/A

Description

Specifies the instantaneous bandwidth of the device in hertz (Hz). The instantaneous bandwidth is the effective real-time bandwidth of the signal path for your configuration.

Specify the maximum instantaneous bandwidth needed for your measurement. NI-RFSA coerces the actual IF filter to use based on other measurement constraints such as the NIRFSA_ATTR_IF_FILTER_BANDWIDTH attribute and the NIRFSA_ATTR_DIGITAL_IF_EQUALIZATION_ENABLED attribute.

To change the value that NI-RFSA uses for the maximum size of multispan acquisition subspans, use the NIRFSA_ATTR_FFT_WIDTH attribute.

Note Note  If your application uses the PXIe-5622 IF digitizer, your maximum device instantaneous bandwidth is constrained to 50 MHz or 25 MHz, depending on the digitizer option you purchased. If your application uses the PXIe-5624 digitizer, your maximum device instantaneous bandwidth is constrained by the hardware option you purchased and your FPGA image.
PXI-5661—The PXI-5600 RF downconverter instantaneous bandwidth is 20 MHz.

PXIe-5663/5663E—Your maximum allowed instantaneous bandwidth depends on the downconverter center frequency you use. Refer to the PXIe-5601 RF Signal Downconverter Overview for more information about instantaneous bandwidth.

Note Note  For the 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 the instantaneous bandwidth for frequencies less than 120 MHz, which are 20 MHz and 10 MHz respectively.
PXIe-5665—Your maximum allowed instantaneous bandwidth is independent of the downconverter center frequency. Refer to the NI PXIe-5665 Specifications for more information about instantaneous bandwidth.

PXIe-5665 (14 GHz), PXIe-5668—If you have enabled the preselector for the PXIe-5605/5606, the device instantaneous bandwidth value is only a typical specification. For multispan acquisitions, NI-RFSA uses this typical specification as the maximum size for the acquisition subspans.

Note  When used with an external digitizer, the PXIe-5603 and the low band signal path of the PXIe-5605 provide a nominal 80 MHz bandwidth at –6 dB. At frequencies greater than 3.6 GHz, the PXIe-5605 provides a typical bandwidth of 47 MHz at –6 dB with the preselector (YIG-tuned filter) enabled.
Note  For PXIe-5606 devices, the 765 MHz IF filter is available only at center frequencies above 3.6 GHz.
PXIe-5693—This attribute is read-only for the PXIe-5693. The value for the device instantaneous bandwidth depends on the value for the RF preselector filter.

PXIe-5694/PXIe-5667—If your application uses the PXIe-5694 as part of an PXIe-5667 spectrum monitoring receiver or the PXIe-5694 as a stand-alone device, NI-RFSA determines the appropriate IF filter to use based on the value that you set for this attribute.

Note Note  Device instantaneous bandwidths greater than 20 MHz are available only when you bypass all signal conditioning by setting the NIRFSA_ATTR_SIGNAL_CONDITIONING_ENABLED attribute to NIRFSA_VAL_SIGNAL_CONDITIONING_BYPASSED.
Device Instantaneous Bandwidth Attribute Value Frequency Range IF Filter
≤30 kHz (NIRFSA_ATTR_IF_CONDITIONING_DOWN_CONVERSION_ENABLED attribute set to NIRFSA_VAL_ENABLED) 30 kHz
>30 kHz and ≤400 kHz 400 kHz
>400 kHz and ≤1.4 MHz 1.4 MHz
>1.4 MHz and ≤5 MHz 5 MHz
>5 MHz and ≤20 MHz 20 MHz
>20 MHz (NIRFSA_ATTR_SIGNAL_CONDITIONING_ENABLED attribute set to NIRFSA_VAL_SIGNAL_CONDITIONING_BYPASSED) Bypass

| :- | :- | PXIe-5644/5645/5646—This attribute is read-only for the PXIe-5644/5645/5646. Refer to the specifications document for your device for more information about instantaneous bandwidth.

PXIe-5840/5841—Your maximum allowed instantaneous bandwidth depends on the downconverter center frequency you use. Refer to the PXIe-5840 Specifications for more information about instantaneous bandwidth. Set this attribute to select different device instantaneous bandwidths for a given downconverter center frequency. The device instantaneous bandwidth that you select is greater than or equal to the requested instantaneous bandwidth. If this attribute is not set, NI-RFSA uses the maximum allowed instantaneous bandwidth.

Default Value: N/A

Supported Devices: PXI-5600, PXIe-5601/5603/5605/5606 (external digitizer mode), PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5693/5694, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

PXIe-5830 Frequency and Bandwidth Selection

PXIe-5831/5832 Frequency and Bandwidth Selection

PXIe-5841 Frequency and Bandwidth Selection

IQ

NIRFSA_ATTR_IQ_CARRIER_FREQUENCY

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W niRFSA_ConfigureIQCarrierFrequency

Description

Specifies the expected carrier frequency of the incoming signal for demodulation. The NI-RFSA device tunes to this frequency. NI-RFSA may coerce this value based on hardware settings and the RF downconverter specifications.

Note Note  For the PXIe-5645, this attribute is ignored if you are using the I/Q ports.
Units: hertz (Hz)

Default Values:

PXIe-5644/5645/5646, PXIe-5840/5841: 1 GHz

PXIe-5820: 0 Hz

PXIe-5830/5831/5832: 6.5 GHz

All other devices: 100 MHz

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

Carrier Wave

I/Q Modulation

NIRFSA_ATTR_SIGNAL_BANDWIDTH

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W None

Description

Specifies the bandwidth of the input signal around the I/Q carrier frequency. This value must be less than or equal to (0.8 × I/Q rate).

NI-RFSA defines signal bandwidth as twice the maximum I/Q signal deviation from 0 Hz. Usually, the baseband signal center frequency is 0 Hz. In such cases, the signal bandwidth is simply the baseband signal's minimum frequency subtracted from its maximum frequency, or fmax - fmin.

If you do not set this attribute, NI-RFSA uses the maximum available signal bandwidth. Depending on your device settings, setting this attribute enables certain optimizations. Based on the specified signal bandwidth, NI-RFSA decides the minimum equalized bandwidth and equalizer gain.

Note Note  You must set this attribute to enable the NIRFSA_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET_MODE attribute.
Ensure you set the signal bandwidth wide enough to encompass all significant anticipated input power. In cases where NI-RFSA optimizes the input gain based on the signal bandwidth, significant input power outside the signal bandwidth can lead to clipping and associated overflow warnings if you do not have enough margin in your reference level.

Units: Hz

Default Value: 0 Hz

Supported Devices: PXIe-5820/5830/5831/5832/5840/5841

Related Topics

PXIe-5830 Frequency and Bandwidth Selection

PXIe-5831/5832 Frequency and Bandwidth Selection

PXIe-5841 Frequency and Bandwidth Selection

NIRFSA_ATTR_IQ_RATE

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W niRFSA_ConfigureIQRate

Description

Specifies the I/Q rate for the acquisition. The value is expressed in samples per second (S/s).

Refer to the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute for more information about device specific instantaneous bandwidth limits. You can also refer to the NI PXIe-5665 Specifications for more information about instantaneous bandwidth device specifications.

Note

Note  For the PXIe-5663/5663E/5665/5667/5668, NI-RFSA enables dithering by default. At I/Q rates above 50 MS/s, the dither noise can affect phase coherency performance and leak into the lower frequencies and the upper frequencies of the IF passband. Refer to the NIRFSA_ATTR_DIGITIZER_DITHER_ENABLED attribute for more information about dithering.

For the PXIe-5663/5663E/5665/5667, when you set the NIRFSA_ATTR_DIGITIZER_SAMPLE_CLOCK_TIMEBASE_SOURCE attribute to NIRFSA_VAL_ONBOARD_CLOCK_STR, the downconverter instantaneous bandwidth is greater than or equal to the coerced I/Q rate times 0.8. For the PXIe-5665, the actual signal bandwidth is further limited by the combination of the chosen IF filter and anti-aliasing filter.
**PXI-5661—**You should not need to configure an I/Q rate higher than 25 megasamples per second (MS/s) because the PXI-5600 RF downconverter bandwidth is 20 MHz. If you configure a higher I/Q rate, you may see aliasing effects at negative frequencies because the IF frequency of the PXI-5600 is 15 MHz.

**PXIe-5663/5663E—**Your maximum allowed instantaneous bandwidth depends on the I/Q carrier frequency you use. Refer to the PXIe-5601 RF downconverter overview for more information about instantaneous bandwidth.

**PXIe-5665—**Your maximum allowed instantaneous bandwidth depends on the downconverter center frequency if you have enabled the preselector (YIG-tuned filter).

PXIe-5667—Your maximum allowed instantaneous bandwidth depends on the selected RF preselector filter and whether the preselector on the RF downconverter is enabled.

**PXIe-5668—**Your maximum allowed instantaneous bandwidth depends on the downconverter center frequency you use and whether or not you enable the highpass filter or preselector (YIG-tuned filter).

Units: S/s

Default Value: 1 MHz

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

I/Q Modulation

NIRFSA_ATTR_NUMBER_OF_SAMPLES_IS_FINITE

Specific Attribute

Data
type		 Access High Level Functions
ViBoolean R/W niRFSA_ConfigureNumberOfSamples

Description

Specifies whether the device acquires a finite number of samples or acquires continuously.

Defined Values:

VI_TRUE Acquire a finite number of samples.
VI_FALSE Acquire continuously until you abort the acquisition.
Default Value: VI_TRUE

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

I/Q Modulation

NIRFSA_ATTR_NUMBER_OF_SAMPLES

Specific Attribute

Data
type		 Access High Level Functions
ViInt64 R/W niRFSA_ConfigureNumberOfSamples

Description

Specifies the number of samples to acquire. This attribute is valid only if the NIRFSA_ATTR_NUM_SAMPLES_IS_FINITE attribute is set to VI_TRUE.

Default Value: 1,000

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

I/Q Modulation

NIRFSA_ATTR_NUMBER_OF_RECORDS_IS_FINITE

Specific Attribute

Data
type		 Access High Level Functions
ViBoolean R/W niRFSA_ConfigureNumberOfRecords

Description

Specifies whether the device stops after acquiring the specified number of records or acquires records continuously.

Defined Values:

VI_TRUE Acquire a finite number of records.
VI_FALSE Acquire records continuously until you abort the acquisition.
Default Value: VI_TRUE

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

I/Q Modulation

NIRFSA_ATTR_ALLOW_MORE_RECORDS_THAN_MEMORY

Specific Attribute

Data
type		 Access High Level Functions
ViBoolean R/W None

Description

Specifies whether to allow the device to acquire more records than can fit in the device memory of the PXIe-5622/5624.

Note Note  If you set the attribute to FALSE and attempt to acquire more records than can fit into the PXIe-5622/5624 device memory, NI-RFSA returns an error. If this attribute is set to TRUE, NI-RFSA returns an error only in the event of an acquisition buffer overflow.
Note Note  This attribute is always set to VI_TRUE for the PXIe-5644/5645/5646 and PXIe-5820/5830/5831/5832/5840/5841.
Defined Values:
VI_TRUE Allows acquisition of more records than fit in device memory.
VI_FALSE Does not allow acquisitions of more records than fit in device memory.
Default Value: VI_FALSE

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_NUMBER_OF_RECORDS

Specific Attribute

Data
type		 Access High Level Functions
ViInt64 R/W niRFSA_ConfigureNumberOfRecords

Description

Specifies the number of records to acquire if the NIRFSA_ATTR_NUM_RECORDS_IS_FINITE attribute is set to VI_TRUE.

Default Value: 1

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

I/Q Modulation

NIRFSA_ATTR_PHASE_OFFSET

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W None

Description

Specifies the offset to apply to the initial I and Q phases.

Valid Values: –180 to 180

Default Value: 0

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

IQ Advanced

NIRFSA_ATTR_CONTIGUOUS_MULTIRECORD

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

This attribute is not for customer use.

Spectrum

NIRFSA_ATTR_SPECTRUM_CENTER_FREQUENCY

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W niRFSA_ConfigureSpectrumFrequencyCenterSpan

Description

Specifies the center frequency in a spectrum acquisition. The value is expressed in hertz (Hz). An acquisition consists of a span of data surrounding the center frequency.

Note Note  Use this attribute to tune the downconverter when using external digitizer mode.
Units: hertz (Hz)

Default Values:

PXIe-5694: 193.6 MHz

PXIe-5820: 0 Hz

PXIe-5830/5831/5832: 6.5 GHz

All other devices: 1 GHz

Supported Devices: PXI-5600, PXIe-5601/5603/5605/5606 (external digitizer mode), PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5693/5694/5698, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_SPECTRUM_SPAN

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W niRFSA_ConfigureSpectrumFrequencyCenterSpan

Description

Specifies the frequency range of the computed spectrum in hertz (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 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 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

NIRFSA_ATTR_POWER_SPECTRUM_UNITS

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies the units of the power spectrum.

Defined Values:

NIRFSA_VAL_DBM (200) Units are dB with reference to 1 milliwatt.
NIRFSA_VAL_VOLTS_SQUARED (201) Units are in volts squared.
NIRFSA_VAL_DBMV (202) Units are dB with reference to 1 millivolt.
NIRFSA_VAL_DBUV (203) Units are dB with reference to 1 microvolt.
NIRFSA_VAL_VOLTS (204) Units are in volts.
NIRFSA_VAL_WATTS (205) Units are in watts.
Default Value: NIRFSA_VAL_DBM

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_RESOLUTION_BANDWIDTH

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W niRFSA_ConfigureResolutionBandwidth

Description

Specifies the resolution along the x-axis of the spectrum. NI-RFSA uses the resolution bandwidth value to determine the acquisition size. If specified, the NIRFSA_ATTR_NUMBER_OF_SPECTRAL_LINES attribute value overrides this value.

Units: hertz (Hz)

Default Value: 100 kHz

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_RESOLUTION_BANDWIDTH_TYPE

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies how the NIRFSA_ATTR_RESOLUTION_BANDWIDTH attribute is expressed.

Defined Values:

NIRFSA_VAL_RBW_3DB (300) Defines the resolution bandwidth (RBW) in terms of the 3 dB bandwidth of the window specified by the NIRFSA_ATTR_FFT_WINDOW_TYPE attribute.
NIRFSA_VAL_RBW_6DB (301) Defines the RBW in terms of the 6 dB bandwidth of the window specified by the NIRFSA_ATTR_FFT_WINDOW_TYPE attribute.
NIRFSA_VAL_RBW_BIN_WIDTH (302) Defines the RBW in terms of the display resolution, which is the ratio of the sampling frequency to the number of samples that you acquire.
NIRFSA_VAL_RBW_ENBW (303) Defines the RBW in terms of the equivalent noise bandwidth (ENBW) of the window specified by the NIRFSA_ATTR_FFT_WINDOW_TYPE attribute.
Default Value: NIRFSA_VAL_RBW_3DB

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_NUMBER_OF_SPECTRAL_LINES

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies the number of spectral lines expected with the current power spectrum configuration. If you do not configure this attribute, NI-RFSA selects an appropriate value based on the NIRFSA_ATTR_RESOLUTION_BANDWIDTH attribute. If you configure this attribute, NI-RFSA coerces the NIRFSA_ATTR_RESOLUTION_BANDWIDTH value based on the number of spectral lines requested and the value of the NIRFSA_ATTR_SPECTRUM_SPAN attribute.

Default Value: N/A

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_SPECTRUM_AVERAGING_MODE

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies the averaging mode for the spectrum acquisition.

Defined Values:

NIRFSA_VAL_NO_AVERAGING (400) Configures NI-RFSA to perform no averaging on acquisitions.
NIRFSA_VAL_RMS_AVERAGING (401) Configures NI-RFSA for root-mean-square (RMS) averaging. RMS averaging reduces signal fluctuations but not the noise floor. RMS averaging averages the energy, or power, of the signal. This averaging prevents noise floor reduction and gives averaged RMS quantities of single-channel measurements zero phase. RMS averaging for dual-channel measurements preserves important phase information.
NIRFSA_VAL_VECTOR_AVERAGING (402) Configures NI-RFSA for vector averaging. Vector averaging reduces noise from synchronous signals. Vector averaging computes the average of complex quantities directly, which means that it allows separate averaging for real and imaginary parts. Complex averaging such as vector averaging reduces noise and usually requires a trigger to improve block-to-block phase coherence.
NIRFSA_VAL_PEAK_HOLD_AVERAGING (403) Configures NI-RFSA for peak-hold averaging. Peak-hold averaging retains the RMS peak levels of the averaged quantities. The peak-hold averaging process performs peak-hold at each frequency bin separately to retain peak RMS levels from one FFT record to the next.
Default Value: NIRFSA_VAL_NO_AVERAGING

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_SPECTRUM_NUMBER_OF_AVERAGES

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies the number of acquisitions to average. The averaging process returns the final result after the number of averages is complete.

Default Value: 10

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_FFT_WINDOW_TYPE

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies the time-domain window type.

Defined Values:

NIRFSA_VAL_UNIFORM (500) No window is applied.
NIRFSA_VAL_HANNING (501)

The Hanning window is useful for analyzing transients longer than the time duration of the window, and also for general-purpose applications. A Hanning window is applied to the waveform using the following equation:

y[i] = 0.5 × x[i] × [1–cos(w)]

where w = (2)i/n and n = waveform size.
NIRFSA_VAL_HAMMING (502)

A Hamming window is applied to the waveform using the following equation:

y[i] = x[i] × [0.54 – 0.46cos(w)]

where w = (2)i/n and n = the waveform size.
Note Note  Hanning and Hamming windows are somewhat similar. However, in the time domain, the Hamming window does not get as close to zero near the edges as does the Hanning window.

| :- | :- | |NIRFSA_VAL_BLACKMAN_HARRIS (503)|

A Blackman-Harris window is applied to the waveform using the following equation:

y[i] = x[i] × [0.42323 – 0.49755cos(w) + 0.07922cos(2w)]

where w = (2)i/n and n = the waveform size.

| |NIRFSA_VAL_EXACT_BLACKMAN (504)|

An Exact Blackman window is applied to the waveform using the following equation:

y[i] = x[i] × [a0 – a1cos(w) + a2cos(2w)]

where   w = (2)i/n

n = the waveform size

a0 = 7938/18608

a1 = 9240/18608

a2 = 1430/18608

| |NIRFSA_VAL_BLACKMAN (505)|

A Blackman window is useful for analyzing transient signals, and provides similar windowing to Hanning and Hamming windows but adds one additional cosine term to reduce ripple. A Blackman window is applied to the waveform using the following equation:

y[i] = x[i] × [0.42 – 0.50cos(w) + 0.08cos(2w)]

where w = (2)i/n and n = the waveform size.

| |NIRFSA_VAL_FLAT_TOP (506)|

The fifth-order Flat Top window has the best amplitude accuracy of all the window functions. The increased amplitude accuracy (±0.02 dB for signals exactly between integral cycles) is at the expense of frequency selectivity. The Flat Top window is most useful in accurately measuring the amplitude of single frequency components with little nearby spectral energy in the signal.

A fifth-order Flat Top window is applied to the waveform using the following equation:

y[i] = x[i] × [a0 – a1cos(w) + a2cos(2w) – a3cos(3w) + a4cos(4w)]

where   w = (2)i/n

n is the waveform size

a0 = 0.215578948

a1 = 0.41663158

a2 = 0.277263158

a3 = 0.083578947

a4 = 0.006947368.

| |NIRFSA_VAL_4_TERM_BLACKMAN_HARRIS (507)|

A 4-term Blackman-Harris window is a general purpose window; it has side-lobe rejection in the upper 90 dB, with moderately wide side lobe. A 4-term Blackman Harris window is applied to the waveform using the following equation:

w(i) = x[i] × [a0 – a1cos(w) + a2cos(2w) – a3cos(3w)]

where w = (2i)/N

N is the waveform size

a0 = 0.35875

a1 = 0.48829

a2 = 0.14128

a3 = 0.01168

| |NIRFSA_VAL_7_TERM_BLACKMAN_HARRIS (508)|

A 7-term Blackman-Harris window has the highest dynamic range; it is ideal for signal-to-noise ratio applications. A 7-term Blackman Harris window is applied to the waveform using the following equation:

y[i] = x[i] × [a0 – a1cos(w) + a2cos(2w) – a3cos(3w) + a4cos(4w) – a5cos(5w) + a6cos(6w)]

where   w = (2)i/n

n is the waveform size

a0 = 0.27105140069342

a1 = 0.43329793923448

a2 = 0.21812299954311

a3 = 0.06592544638803

a4 = 0.01081174209837

a5 = 0.00077658482522

a6 = 0.00001388721735.

| |NIRFSA_VAL_LOW_SIDE_LOBE (509)|

The Low Side Lobe window further reduces the size of the main lobe. The following equation defines the Low Side Lobe window.

where   N is the length of window

w = (2n)/N

a0 = 0.323215218

a1 = 0.471492057

a2 = 0.17553428

a3 = 0.028497078

a4 = 0.001261367

| |NIRFSA_VAL_GAUSSIAN (510)|

A Gaussian window is applied to the waveform using the following equation:

y[i] = x[i] × e((-0.5(i - (N-1)/0.5) / (σ(N-1)/0.5))

where N is the length of the window and σ ≤ 0.5

 

| |NIRFSA_VAL_KAISER_BESSEL (511)|

A Kaiser-Bessel window is applied to the waveform using the following equation:

y[i] = x[i] × I0 × (π × α(1 - (2i/ (N-1)-1)2)0.5) / (I0 × π × α)

where i ≥ 0 and i ≤ N-1

N is the length of the window

π determines the shape of the window

I0 is the zeroth order Modified Bessel function of the first kind

 

| Default Values:

PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5668, PXIe-5820/5830/5831/5832/5840/5841: NIRFSA_VAL_7_TERM_BLACKMAN_HARRIS

PXIe-5667: NIRFSA_VAL_4_TERM_BLACKMAN_HARRIS

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5668, PXIe-5820/5830/5831/5832/5840/5841

Related Topics

Resolution Bandwidth

NIRFSA_ATTR_FFT_WINDOW_SHAPE_FACTOR

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 RO None

Description

Returns the shape factor of the window used in the fast Fourier transform (FFT). The window shape factor is defined as the ratio of the 60 dB to 6 dB bandwidths.

The following table shows the shape factor for each NI-RFSA FFT window type.

Window Type Shape Factor
Uniform 1.57:1
Hanning 1.94:1
Hamming 2.13:1
Exact Blackman 2.52:1
Flat Top 2.0:1
4-term Blackman-Harris 2.5:1
7-term Blackman-Harris 4.1:1
Low Side Lobe 2.78:1
Gaussian 2.3:1
Kaiser Bessel 2.55:1
Default Value: N/A

Supported Devices: PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5840/5841

NIRFSA_ATTR_FFT_WINDOW_SIZE

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 RO None

Description

Returns the size of the window used in the fast Fourier transform (FFT), in terms of the number of samples in the window.

Default Value: N/A

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_FFT_SIZE

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 RO None

Description

Returns the size of the fast Fourier transform (FFT).

Default Value: N/A

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_SPECTRUM_OSP_SAMPLING_RATIO

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W None

Description

Specifies the oversampling ratio used by the digitizer onboard signal processing (OSP) when you are in spectrum acquisition mode. This attribute allows you to acquire a larger bandwidth in hardware and reduce that bandwidth in software, decreasing the possibility of hardware data path overflows.

PXIe-5644/5645/5646—The only valid value for this attribute is 1.

Default Value: 1.0

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_FFT_WIDTH

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W None

Description

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

Note  The maximum FFT width when using the PXIe-5622 is constrained to 50 MHz or 25 MHz, depending on the digitizer option you purchased. The maximum FFT width when using thing PXIe-5624 is constrained to 400 MHz or 765 MHz, depending on the digitizer configuration.
Note  You can use the NIRFSA_ATTR_FFT_WIDTH attribute with in-band retuning. For more information about in-band retuning, refer to the NIRFSA_ATTR_DOWNCONVERTER_CENTER_FREQUENCY attribute.
NI-RFSA 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. An RF vector signal analyzer can acquire a bandwidth only within the device instantaneous bandwidth frequency. If the span you choose is greater than the device instantaneous bandwidth, NI-RFSA 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. If you read the NIRFSA_ATTR_FFT_WIDTH attribute without setting it, NI-RFSA returns the value of the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute.

Valid Values:

The lower limit for all FFT width supported devices using the PXIe-5622 IF digitizer is 7.325 kHz. The lower limit for all FFT width supported devices using the PXIe-5624 IF digitizer is 400 MHz or 800 MHz, depending on the FPGA image that is downloaded upon opening the session to the PXIe-5624 IF digitizer.

PXIe-5663/5663E—The FFT width upper limit for the PXIe-5663/5663E depends on the downconverter center frequency and on the module revision of the PXIe-5601 as illustrated in the following table. Refer to the Identifying Module Revision topic for more information about determining which revision of the PXIe-5601 RF downconverter you have installed.

Downconverter Center Frequency PXIe-5601 Instantaneous Bandwidth FFT Width Upper Limit
10 MHz to <120 MHz 10 MHz 10 MHz (Revision E), 20 MHz* (Revision G or later)
120 MHz to <330 MHz 20 MHz 20 MHz (Revision E), 30 MHz* (Revision G or later)
330 MHz to <6.6 GHz 50 MHz 50 MHz
*National Instruments does not guarantee device specifications if you set the NIRFSA_ATTR_FFT_WIDTH attribute greater than the warranted instantaneous bandwidth specification.
PXIe-5665/5667/5668—The upper limit of the FFT width is the maximum device instantaneous bandwidth.
Note

Note  If you do not set the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute, NI-RFSA determines the appropriate IF filter to use based on the value that you set for the FFT width and your specific device. Refer to the following tables to determine which IF filter corresponds to each FFT width frequency range for your device.

If you set the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute, NI-RFSA selects the appropriate IF filter based on the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute and the NIRFSA_ATTR_FFT_WIDTH attribute determines how much bandwidth of that filter is used during acquisition. Refer to the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute to determine which IF filter corresponds to the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute setting.
Device NIRFSA_ATTR_FFT_WIDTH Attribute Value Frequency Range IF Filter
PXIe-5603/5665 (3.6 GHz) ≤300 kHz 300 kHz IF filter
>300 kHz and ≤5 MHz Through IF filter
>5 MHz Through IF filter
PXIe-5605/5665 (14 GHz) ≤300 kHz 300 kHz IF filter
>300 kHz and ≤5 MHz 5 MHz IF filter
>5 MHz Through IF filter
PXIe-5667 ≤30 kHz (NIRFSA_ATTR_IF_CONDITIONING_DOWN_CONVERSION_ENABLED attribute set to NIRFSA_VAL_ENABLED) 30 kHz
>30 kHz and ≤400 kHz 400 kHz
>400 kHz and ≤1.4 MHz 1.4 MHz
>1.4 MHz and ≤5 MHz 5 MHz
>5 MHz and ≤20 MHz 20 MHz
>20 MHz (NIRFSA_ATTR_SIGNAL_CONDITIONING_ENABLED attribute set to NIRFSA_VAL_SIGNAL_CONDITIONING_BYPASSED) Bypass
PXIe-5668 ≤300 kHz 300 kHz
>300 kHz and ≤5 MHz 5 MHz
>5 MHz and ≤100 MHz 100 MHz
>100 MHz and ≤320 MHz 320 MHz
>320 MHz and ≤400 MHz (high band) 765 MHz
(low band) 320 MHz

| :- | :- |

Note  At frequencies greater than 3.6 GHz, the PXIe-5605 provides a typical bandwidth of 47 MHz at –6 dB with the preselector enabled. The NIRFSA_ATTR_FFT_WIDTH attribute can override the typical bandwidth of the PXIe-5605 up to 57 MHz using an external digitizer and up to 50 MHz or 25 MHz depending on the PXIe-5622 digitizer option you purchased. The increase in bandwidth results in faster signal acquisitions, but amplitude accuracy is decreased for spectrum acquisitions, and magnitude and phase accuracy is decreased for I/Q acquisitions. National Instruments does not guarantee device specifications if you set the NIRFSA_ATTR_FFT_WIDTH attribute greater than the warranted instantaneous bandwidth specification.
Note  When using the PXIe-5606, the 765 MHz IF filter is only available at center frequencies of 3.6 GHz and above.
Default Value: N/A

Supported Devices: PXIe-5663/5663E/5665/5667/5668

NIRFSA_ATTR_SMOOTH_SPECTRUM_ENABLED

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies that an optimized IF filtering selection is made at different spectrum frequency ranges during spectrum acquisition.

The IF filter used depends on the configured RF center frequency, as shown in the following table.

Center Frequency IF Filter
≥20 Hz and <80 MHz 300 kHz
≥80 MHz 50 MHz
Note  Setting this attribute to Enabled prevents you from setting NIRFSA_ATTR_IF_FILTER_BANDWIDTH or NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH.
Defined Values:
NIRFSA_VAL_DISABLED The attribute is disabled.
NIRFSA_VAL_ENABLED The attribute is enabled.
Default Value: NIRFSA_VAL_DISABLED

Supported Devices: PXIe-5665/5668

NIRFSA_ATTR_SUBSPAN_OVERLAP

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W N/A

Description

Specifies the amount of overlap between consecutive subspans in a multispan acquisition. Overlapping subspans can reduce the power level of spurs in acquired data. The value you specify determines the amount of shift as a percentage of subspan width.

Specifying a value of 0 disables subspan overlap. In this case, NI-RFSA uses either a single-span acquisition or a multispan acquisition without overlap, depending on the frequency range requested and the current device settings.

Specifying a value greater than 0 causes NI-RFSA to use a multispan acquisition with the specified overlap even in situations in which it would normally use a single-span acquisition. NI-RFSA acquires data within the overlapped percentage and uses the minimum of the acquired values.

Note NI-RFSA may apply further shifts to the specified value to accommodate fixed-frequency edges of components such as preselectors.
Valid Values:

PXIe-5665/5668: 0 to <100

PXIe-5820/5830/5831/5832/5840/5841: 0

Default Value: 0

Supported Devices: PXIe-5665/5668, PXIe-5820/5830/5831/5832/5840/5841

Fetch

NIRFSA_ATTR_FETCH_RELATIVE_TO

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies the reference location within the acquired record from which to begin fetching.

Defined Values:

NIRFSA_VAL_MOST_RECENT_SAMPLE (700) Fetching occurs relative to the most recently acquired data. The value of the NIRFSA_ATTR_FETCH_OFFSET attribute must be negative.
NIRFSA_VAL_FIRST_SAMPLE (701) Fetching occurs at the first sample acquired by the device. If the device wraps its buffer, the first sample is no longer available. In this case, NI-RFSA returns an error if the fetch offset is in the overwritten data.
NIRFSA_VAL_REF_TRIGGER (702) Fetching occurs relative to the Reference Trigger. This value behaves like NIRFSA_VAL_FIRST_SAMPLE if no Reference Trigger is configured.
NIRFSA_VAL_FIRST_PRETRIGGER_SAMPLE (703) Fetching occurs relative to the first pretrigger sample acquired.
NIRFSA_VAL_CURRENT_READ_POSITION (704) Fetching occurs after the last fetched sample.
Default Value: N/A

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_FETCH_OFFSET

Specific Attribute

Data
type		 Access High Level Functions
ViInt64 R/W None

Description

Specifies the offset relative to the position specified by the NIRFSA_ATTR_FETCH_RELATIVE_TO attribute from which to start fetching data. Offset can be a positive or negative value.

Default Value: 0

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_RECORDS_DONE

Specific Attribute

Data
type		 Access High Level Functions
ViInt64 RO None

Description

Returns the number of records the RF vector signal analyzer has acquired.

Default Value: N/A

Supported Devices: PXIe-5644/5645/5646, PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_DATA_TRANSFER_MAXIMUM_BANDWIDTH

Specific Attribute

Datatype Access High Level Functions
ViReal64 R/W None

Description

Specifies the maximum bandwidth that the device can consume.

Note Note  The NI device limits itself to transfer fewer bytes per second on the PCI Express bus than the value you specify for this attribute.
Default Value: N/A

Supported Devices: PXI-5661, PXIe-5663/5663E/5665

NIRFSA_ATTR_DATA_TRANSFER_BLOCK_SIZE

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies the maximum number of samples to transfer at one time from the device to host memory. Increasing this number should result in better fetching performance because the driver does not need to restart the transfers as often. However, increasing this number may increase the amount of page-locked memory required from the system.

Default Values:

PXIe-5668—0x2,000,000

All Other Devices—0x400,000

Supported Devices: PXI-5661, PXIe-5663/5663E/5665/5667/5668

NIRFSA_ATTR_HOST_DMA_BUFFER_SIZE

Specific Attribute

Data
type		 Access High Level Functions
ViInt64 R/W None

Description

Specifies the size of the DMA buffer in computer memory, in bytes. To set this attribute, the NI-RFSA device must be in the Configuration state.

A sufficiently large host DMA buffer improves performance by allowing large fetches to be transferred more efficiently.

Default Value: 8 MB

Supported Devices: PXI-5820/5830/5831/5840/5841

Advanced

NIRFSA_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET_MODE

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Specifies whether to allow NI-RFSA to select the downconveter frequency offset. You can either set an offset yourself or let NI-RFSA select one for you.

Placing the downconverter center frequency outside the bandwidth of your input signal can help avoid issues such as LO leakage.

To set an offset yourself, set this attribute to NIRFSA_VAL_AUTOMATIC or NIRFSA_VAL_USER_DEFINED, and set either the NIRFSA_ATTR_DOWNCONVERTER_CENTER_FREQUENCY or the NIRFSA_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET attributes.

To allow NI-RFSA to automatically select the downconverter frequency offset, set this attribute to NIRFSA_VAL_AUTOMATIC or NIRFSA_VAL_ENABLED and configure the NIRFSA_ATTR_SIGNAL_BANDWIDTH attribute to describe your expected input signal. The signal bandwidth must be no greater than half the specified value of the NIRFSA_ATTR_DEVICE_INSTANTANEOUS_BANDWIDTH attribute, minus a device-specific guard band. Do not set the NIRFSA_ATTR_DOWNCONVERTER_CENTER_FREQUENCY or NIRFSA_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET attributes. If all conditions are met, NI-RFSA places the downconverter center frequency outside the signal bandwidth. Set this attribute to NIRFSA_VAL_ENABLED if you want to receive an error any time NI-RFSA is unable to apply automatic offset.

When you set an offset yourself or do not use an offset, the reference frequency for gain is near the downconverter center frequency, and NIRFSA_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET_MODE returns NIRFSA_VAL_USER_DEFINED. When NI-RFSA automatically sets an offset, the reference frequency for gain is the I/Q carrier frequency, and NIRFSA_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET_MODE returns NIRFSA_VAL_ENABLED. Refer to the specifications document for your device for more information about gain, flatness, and reference frequencies.

Note Note  Below 120 MHz, the PXIe-5841 does not use an LO and NIRFSA_VAL_ENABLED is unavailable. Refer to the PXIe-5841 Automatic Frequency Offset topic for more information about using an automatic offset with an external LO.
Defined Values:
NIRFSA_VAL_ENABLED (1901) NI-RFSA places the downconverter center frequency outside of the signal bandwidth if the NIRFSA_ATTR_SIGNAL_BANDWIDTH attribute has been set and can be avoided. NI-RFSA returns an error if the NIRFSA_ATTR_SIGNAL_BANDWIDTH attribute has not been set, or if the signal bandwidth is too large.
NIRFSA_VAL_AUTOMATIC (1903) NI-RFSA places the downconverter center frequency outside of the signal bandwidth if the NIRFSA_ATTR_SIGNAL_BANDWIDTH attribute has been set and can be avoided.
NIRFSA_VAL_USER_DEFINED (1904) NI-RFSA uses the offset that you specified with the NIRFSA_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET or NIRFSA_ATTR_DOWNCONVERTER_CENTER_FREQUENCY attributes.
Default Value: NIRFSA_VAL_AUTOMATIC

Supported Devices: PXIe-5830/5831/5832/5841

Related Topics

PXIe-5830 Automatic Frequency Offset

PXIe-5831/5832 Automatic Frequency Offset

PXIe-5841 Automatic Frequency Offset

NIRFSA_ATTR_DOWNCONVERTER_CENTER_FREQUENCY

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 R/W None

Description

Enables in-band retuning and specifies the current frequency, in hertz (Hz), of the RF downconverter. If you set this attribute, any measurements outside the instantaneous bandwidth of the device are invalid. To disable in-band retuning, reset the attribute or call the niRFSA_ResetDevice function.

After you set this attribute, the downconverter is locked to that frequency until the value is changed or the attribute is reset. Locking the downconverter to a fixed value allows frequencies within the instantaneous bandwidth of the downconverter to be measured with minimal overhead, decreasing tuning time.

Valid Values: Any supported tuning frequency of the device

PXIe-5820: The only valid value for this attribute is 0 Hz.

Default Value:

PXIe-5694: The default value for the PXIe-5694 is 193.6 MHz unless you set the NIRFSA_ATTR_SIGNAL_CONDITIONING attribute to NIRFSA_VAL_SIGNAL_CONDITIONING_BYPASSED, in which case the default value is 187.5 MHz.

All other devices: The carrier frequency or spectrum center frequency. NI-RFSA sets this attribute to the default value based on the value of the NIRFSA_ATTR_ACQUISITION_TYPE attribute.

Supported Devices: PXIe-5601/5603/5605/5606 (external digitizer mode), PXIe-5644/5645/5646, PXIe-5663/5663E/5665/5667/5668, PXIe-5694, PXIe-5820/5830/5831/5832/5840/5841

NIRFSA_ATTR_IF_OUTPUT_FREQUENCY

Specific Attribute

Data
type		 Access High Level Functions
ViReal64 RO None

Description

Returns the center frequency of the IF output signal that corresponds to the configured RF center frequency.

The downconverter translates the RF input frequency to the IF output frequency by mixing it with the LO signal. The nominal values for the IF output frequency are shown in the following table.

Downconverter Nominal IF Output Frequency
PXI-5600 15 MHz
PXIe-5601 53 MHz or 187.5 MHz
PXIe-5603 187.5 MHz or 199 MHz
PXIe-5605 187.5 MHz, 190 MHz, or 199 MHz
PXIe-5606 187.5 MHz, 190 MHz, 199 MHz, 507.5 MHz, or 730 MHz
PXIe-5694

NIRFSA_ATTR_SIGNAL_CONDITIONING_ENABLED set to NIRFSA_VAL_SIGNAL_CONDITIONING_ENABLED and NIRFSA_ATTR_IF_CONDITIONING_DOWN_CONVERSION_ENABLED set to NIRFSA_VAL_DISABLED: 193.6 MHz

NIRFSA_ATTR_IF_CONDITIONING_DOWN_CONVERSION_ENABLED set to NIRFSA_VAL_ENABLED: 21.4 MHz

NIRFSA_ATTR_SIGNAL_CONDITIONING_ENABLED set to NIRFSA_VAL_SIGNAL_CONDITIONING_BYPASSED: 162.5 MHz to 212.5 MHz
The coarse nature of the LO settings can cause the downconverter to be unable to tune to the exact LO frequency that would produce the nominal IF output frequency. Any coercion in the actual LO frequency results in the IF output frequency being slightly off from the nominal value.

Additionally, if you use the NIRFSA_ATTR_DOWNCONVERTER_CENTER_FREQUENCY and NIRFSA_ATTR_LO_FREQUENCY attributes to program the downconverter, the IF output frequency could vary from the nominal value. NI-RFSA adjusts the acquired spectrum or I/Q data for the difference between nominal and actual IF output frequency. If you use an external digitizer with a RF downconverter, use this attribute to specify the actual IF output frequency.

Default Value: N/A

Supported Devices:PXI-5600, PXIe-5601/5603/5605/5606 (external digitizer mode), PXI-5661, PXIe-5663/5663E/5665/5667/5668, PXIe-5694

NIRFSA_ATTR_ALLOW_OUT_OF_SPECIFICATION_USER_SETTINGS

Specific Attribute

Data
type		 Access High Level Functions
ViInt32 R/W None

Description

Enables or disables warnings and errors when you set frequency, power, or bandwidth values beyond the limits of the NI-RFSA device specifications. When you set this attribute to NIRFSA_VAL_ENABLED, the driver does not report out-of-specification warnings and errors.

Defined Values:

NIRFSA_VAL_DISABLED The attribute is disabled.
NIRFSA_VAL_ENABLED The attribute is enabled.
Default Value: NIRFSA_VAL_DISABLED

Supported Devices: PXIe-5820/5830/5831/5840/5841

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