Specifies an offset from the center frequency value for the downconverter. Use this property to offset the measurement away from the LO leakage or DC Offset of analyzers that use a direct conversion architecture. You must set this property to half the bandwidth or span of the measurement + guardband. The guardband is needed to ensure that the LO leakage is not inside the analog or digital filter rolloffs. This value is expressed in Hz.

NI recommends using the LO Leakage Avoidance Enabled property instead of the Downconverter Frequency Offset property. The LO Leakage Avoidance Enabled property automatically configures the Downconverter Frequency Offset property to an appropriate offset based on the bandwidth or span of the measurement.

Note This property is not supported on a MIMO session.

You do not need to use a selector string if you want to configure this property 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 Strings topic for information about the string syntax.

Default values: For spectrum acquisition types, the RFmx driver automatically calculates the default value to avoid residual LO power. For I/Q acquisition types, the default value is 0 Hz. If the center frequency is set to a non-multiple of LO Frequency Step Size property, this property is set to compensate for the difference.

The following valid values correspond to their respective devices:
PXIe-5646 -100 MHz to +100 MHz
PXIe-5830/5831/5832/5840/5841 -500 MHz to +500 MHz
PXIe-5842 -1 GHz to +1 GHz
Other devices -42 MHz to +42 MHz

Supported Devices: PXIe-5644/5645/5646, PXIe-5830/5831/5832/5840/5841/5842

Remarks

The following table lists the characteristics of this property.

Short Name Downconverter Frequency Offset (Hz)
Data type cdbl.png
Permissions Read/Write
High-level VIs N/A
Resettable Yes