Enables in-band retuning and specifies the current frequency of the RF downconverter. This value is expressed in Hz.

Syntax

RFMXINSTR_ATTR_DOWNCONVERTER_CENTER_FREQUENCY

Numeric Value

Data Type

Access

Applies To

13

float64

Read/Write

N/A

Remarks


After you set this attribute, the RF 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 without the overhead of retuning the LO and waiting for the LO to settle. This method is called in-band retuning and it has the highest benefit on analyzers that have larger LO settling times. After setting the downconverter center frequency, you can set the center frequency to the frequencies at which you want to take the measurements.

If you want to avoid the LO leakage or DC offset of analyzers that use a direct conversion architecture, it is more convenient to use the RFMXINSTR_ATTR_DOWNCONVERTER_FREQUENCY_OFFSET or RFMXINSTR_ATTR_LO_LEAKAGE_AVOIDANCE_ENABLED attributes.

If you set this attribute, any measurements outside the instantaneous bandwidth of the device are invalid. To disable in-band retuning, reset this attribute or call the RFmxInstr_ResetToDefault function.
Note

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.

The default value is the carrier frequency or spectrum center frequency.

Valid Values: Any supported tuning frequency of the device.
Note

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

Supported devices: PXIe-5644/5645/5646, PXIe-5663/5663E/5665/5668, PXIe-5820/5830/5831/5832/5840/5841/5842