NI 5670 CW Generation Mode Tuning Speed Factors

In CW generation mode, the NI-RFSG driver automatically creates the phase-continuous sine waveform needed for the specified frequency.

In CW generation mode, the following factors contribute to the tuning time:

• Frequency step size (desired frequency - previous frequency)—The upconverter module has different tuning times for various frequency step sizes.
• Requested RF output frequency—The IF waveform size varies, depending on the requested RF output frequency. As the size increases, more time is needed to compute and upload the waveform to the AWG module onboard memory. Refer to the Phase Continuity section for more information about waveform size.
• Frequency tolerance setting—Increasing the frequency tolerance allows the NI-RFSG driver to approximate the desired frequency using a smaller number of waveform cycles, decreasing tuning time. Refer to the Phase Continuity section for more information about waveform cycles.

Typically, the largest delay in tuning to a new frequency is the time it takes the upconverter module to lose its lock on the current frequency and acquire a lock on the new frequency. Depending on the step size, the upconverter module takes different amounts of time to lock to new frequencies.

Tips  The following measures can decrease CW generation mode tuning times: Increase the value of the frequency tolerance by using the frequency tolerance property or NIRFSG_ATTR_FREQUENCY_TOLERANCE attribute as much as allowed by your application. Change your RF frequency in 5 MHz step sizes so that recalculation of the sine waveform is not required.