RFMXINSTR_ATTR_LO_FREQUENCY_STEP_SIZE
- Updated2025-10-13
- 2 minute(s) read
Specifies the step size for tuning the LO phase-locked loop (PLL).
Syntax
RFMXINSTR_ATTR_LO_FREQUENCY_STEP_SIZE
Numeric Value | Data Type | Access | Applies To |
|---|---|---|---|
95 | float64 | Read/Write | N/A |
Remarks
You can only tune the LO frequency in multiples of the LO Frequency Step Size attribute. Therefore, the LO frequency can be offset from the requested center frequency by as much as half of the LO Frequency Step Size attribute. This offset is corrected by digitally frequency shifting the LO frequency to the value requested in RFMXINSTR_ATTR_DOWNCONVERTER_CENTER_FREQUENCY attribute.
For PXIe-5831 with PXIe-5653, PXIe-5832 with PXIe-5653, this attribute is ignored if PXIe-5653 is used as the LO source.
The valid values for this attribute depend on the RFMXINSTR_ATTR_LO_PLL_FRACTIONAL_MODE attribute.
PXIe-5644/5645/5646: If you set the LO PLL Fractional Mode attribute to Disabled, the specified value is coerced to the nearest valid value.
PXIe-5840: If you set the LO PLL Fractional Mode attribute to Disabled, the specified value is coerced to the nearest valid value that is less than or equal to the desired step size.
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 |
This attribute is not supported on a MIMO session.
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.
Default values
Name (value) | Description |
|---|---|
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 | 500 kHz |
PXIe-5842 | 1 Hz |
The default value for PXIe-5831/5832 depends on the frequency range of the selected port for your instrument configuration. Use RFmxInstr_GetAvailablePorts function to get the valid port names.
Supported devices: PXIe-5644/5645/5646, PXIe-5830/5831/5832/5840/5841/5842