API spectrum frequency problems
As shown in the picture, the first 3 columns are my setting parameters(start freq, stop freq, RBW), and the next 3 columns are output data(start freq, stop freq, RBW).
From the picture 1(start freq=1000MHz, end freq=1050MHz), we can see the output frequency are not the same with the input settings, even if the bandwith can be divided by RBW with no remainder, such as line 1(1000KHz), 11(100KHz), 21(10KHz).
But in picture 2(start freq=1000MHz, end freq=1300MHz), the output freq is the same with the input settings.
What is the problem?
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For spans smaller than the realtime bandwidth of the device the measurement may be performed in realtime mode which may cause some minor adjustments to the frequency parameters. In realtime mode the selected center frequency is accurate, but due to technical characteristics the steps between points may not be 100% equal to the selected rbw, and therefore start- and stop-frequency can also be slightly different. The span actually measured may be larger than requested.
For spans larger than the realtime bandwidth the measurement is performed in sweep mode, meaning it consists of multiple physical measurements with different frequency settings that are merged by software, which allows more control over frequency parameters and therefore will usually result in accurate start- and stop-frequencies.
Quote from mm_dev on 12/05/2022, 11:36For spans smaller than the realtime bandwidth of the device the measurement may be performed in realtime mode which may cause some minor adjustments to the frequency parameters. In realtime mode the selected center frequency is accurate, but due to technical characteristics the steps between points may not be 100% equal to the selected rbw, and therefore start- and stop-frequency can also be slightly different. The span actually measured may be larger than requested.
For spans larger than the realtime bandwidth the measurement is performed in sweep mode, meaning it consists of multiple physical measurements with different frequency settings that are merged by software, which allows more control over frequency parameters and therefore will usually result in accurate start- and stop-frequencies.
oh, I see. thanks.
