Tuesday, 1 December 2015

RF Probing issue

When probing around a 500mW 40MHz power amplifier. There is an observation of leaked RF signal on oscilloscope probe, even it is grounded like the picture above.
the leak pickup may caused by the probe ground tail inductance.


And the leaked signal is quite strong, it is suspected that the antenna radiate the carrier around the board. 




This leaked RF pickup may contribute to the unexpected waveform during measurement. This probe is on the collector of transistor.



which is not expected to having voltage dip below 0V


The measurement method needed to be revised.
RF active probe, or differential probe would they help?


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