Device Specific:Vector Signal Transceiver:Signal Path:LO Frequency Step Size (Hz) Property
- Updated2025-05-22
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Device Specific:Vector Signal Transceiver:Signal Path:LO Frequency Step Size (Hz) Property
Short Name: LO Frequency Step Size
Property of niRFSA
Specifies the step size for tuning the local oscillator (LO) phase-locked loop (PLL).
You can only tune the LO frequency by multiples of the LO Frequency Step Size property. For the PXIe-5644/5645/5646 and PXIe-5840, the LO frequency can therefore be offset from the requested center frequency by as much as half of the LO Frequency Step Size property. This offset is corrected by digitally frequency shifting the LO frequency to the value requested in either the IQ Carrier Frequency property or the Spectrum Center Frequency property.
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Note For the PXIe-5831/5832 with PXIe-5653, this property is ignored if the PXIe-5653 is used as the LO source. |
Default Values:
PXIe-5644/5645/5646: 200 kHz
PXIe-5830: 2 MHz
PXIe-5831/5832 (RF port): 8 MHz
PXIe-5831/5832 (IF port): 2 MHz, 4 MHz
PXIe-5840/5841:
- Fractional mode: 500 kHz
- Integer mode: 10 MHz for frequencies less than or equal to 4 GHz. 20 MHz for frequencies greater than 4 GHz.
PXIe-5841 with PXIe-5655: 500 kHz
PXIe-5842: 1 Hz
Supported Devices: PXIe-5644/5645/5646, PXIe-5830/5831/5832/5840/5841/5842
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Note The default value for the PXIe-5831 depends on the frequency range of the selected port for your instrument configuration. Refer to the Instrument Configurations topic for more information about available ports for your hardware configuration. |
The valid values for this property depend on the LO PLL Fractional Mode Enabled property.
PXIe-5644/5645/5646—If you set the LO PLL Fractional Mode Enabled property to Disabled, the specified value is coerced to the nearest valid value.
PXIe-5840—If you set the LO PLL Fractional Mode Enabled property to Disabled, the specified value is coerced to the nearest valid value that is less than or equal to the desired step size.
To use this property for the PXIe-5830/5831/5832 and PXIe-5842 VST with 54 GHz Frequency Extension, you must first use the Active Channel property to specify the name of the channel you are configuring. You can configure LO1 and LO2 channels by using lo1 or lo2 as the channel string, or set the channel string to lo1,lo2 to configure both channels. For all other devices, the only valid value for the channel string is "" (empty string).
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Note For any PXIe-5842 instrument without frequency extension (i.e. no RMM-5585 remote measurement module connected), the only valid value for the channel string is "" (empty string). |
| LO PLL Fractional Mode Enabled Property Setting | LO Frequency Step Size Property Valid Values on PXIe-5644/5645 | LO Frequency Step Size Property Valid Values on PXIe-5646 | LO Frequency Step Size Property Valid Values on PXIe-5840/5841 | LO Frequency Step Size Property Valid Values on PXIe-5830/5831/5832 | LO Frequency Step Size Property Valid Values on PXIe-5841 with PXIe-5655, PXIe-5842* |
|---|---|---|---|---|---|
| Enabled | 50 kHz to 24 MHz | 50 kHz to 25 MHz | 50 kHz to 100 MHz | LO1: 8 Hz to 400 MHz LO2: 4 kHz to 400 MHz | 1 nHz to 50 MHz |
| Disabled | 4 MHz, 5 MHz, 6 MHz, 12 MHz, 24 MHz | 2 MHz, 5 MHz, 10 MHz, 25 MHz | 1 MHz, 5 MHz, 10 MHz, 25 MHz, 50 MHz, 100 MHz | LO1: -- LO2: -- | 1 nHz to 50 MHz |
| * Values up to 100 MHz are coerced to 50 MHz. |
Remarks
The following table lists the characteristics of this property.
| Datatype |  |
| Permissions | Read/Write |
| High-level VIs | N/A |
| Channel-based | Yes |
| Resettable | Yes |