Keysight EXG and MXG X-Series Signal Generators User’s Guide 91Optimize PerformanceUsing Internal Channel Correction (N5172B/82B Only)Using Internal Channel Correction (N5172B/82B Only)The internal channel correction feature flattens the system magnitude and phase response acrossthe maximum bandwidth supported by the instrument (up to 160 MHz BW, depending on theoption). This performance improvement is available at any arbitrary center frequency or amplitudelevel.Correction filter generation and application is performed internally. The correction filtering occursin real time and is applied to live data.There are two correction types: factory and user. The Factory Calibration optimizes the performanceat the front panel RF output connector into a precision 50 ohm load. The User Calibration canextend this performance to a new calibration reference plane and deliver the highest signal qualityto the user’s DUT.This feature also minimizes unwanted baseband images by flattening (and matching) themagnitude and phase response of the I and Q channels from the signal DACs to the IQ modulator.This calibration should be run when the ambient temperature has varied by at least ±5 degreesCelsius from the ambient temperature at which the previous calibration was run.When this feature is off, the box will behave as it always has. When this feature is on, the internalI/Q path is active, the I/Q Correction Optimized Path is RF Output, and the frequency is changed bymore than 1 kHz, the firmware will calculate a channel correction filter. For List/Sweep, thecalculation will be done prior to the first sweep using the specified frequencies when eitherwaveform sweep is active or the baseband is on and the instrument is optimized for the internalpath. This calculation will cache corrections for up to the maximum number of cache points (256).For list/sweep, the sweep will pause and recalculate the correction caches before running again.Additional characteristics of the internal channel correction:— When the internal channel correction is on, arbitrary frequency switching while the baseband ison will take up to an additional 290 ms (72 ms typical) the first time that frequency is specified.After the first time that a frequency is selected, switching to that frequency again takes anadditional 1 ms.There is an internal calibration routine (Factory Calibration) that collectscorrection data for both the baseband and RF magnitude and phase errorsover the entire RF frequency and power level range on any unit withoptions 653, 655, 656, and 657. The internal channel correction cannot beturned on until after the Enhanced Factory Calibration has been executedonce. See “Perform Enhanced Factory Calibration” on page 94.In the case of arbitrary frequency switching, once the correction cache isfull (256 unique frequency points), the oldest frequency corrections will beforgotten as new frequencies are selected.Whenever I/Q Timing Skew, I/Q Delay, Quadrature Angle Adjustment, orthe Int Equalization Filter is adjusted, all caches are forgotten.
