saCompressionWarning not returned

Hi,

While trying to sort out why an algorithm that I have implemented for BB60C is not working with SA44B I have discovered that saGetIQData and saGetSweep do not return saCompressionWarning even if the signal is clearly beyond the reference level specified for automatic gain and attenuator. Both functions return saNoError.

Testing with Spike, the warning is displayed while sweeping the same frequency range, with the same reference level, but I presume that Spike is using saGetPartialSweep. In zero-span mode I have not seen any sign of warning, though.

Hi Catalin,

There are situations (when using the SA44/124) in which the IF overload may not always be reported. Where as with the BB60C which relies on the ADC to tell us of IF overload, the SA overload warning is done by manually checking amplitude values. The ADC does not reliably clamp to the min/max ADC values so we cannot always depend on the large values being clamped properly by the ADC. Additionally, the signal can clamp before it reaches the ADC (in the RF section) and we cannot detect that situation either.

Also note, the Spike software when sweeping will warn you when the signal exceeds the reference level which is not the same as the IF overload warning. This extra warning is not present in zero-span mode.

Sample rates are low enough on the SA devices, you could insert a check on the IQ data to determine if it exceeds some known value (your reference level?).

Let me know if you have additional questions.

Regards,
Andrew

Hi Andrew,

So I need to check the peak value of the samples in the IQ buffer for zero-span mode and the peak spectrum data in sweep mode. With the calibrated samples that should be quite easy.

Many thanks, Catalin

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