richard88
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Ken, Thank you very much for the explanation. I wonder if the passive decoupling network comes from the RF PA or merely due to the output cap of the LDO ? The closed loop transfer function of the LDO with the output cap shaped like a low pass filter and also shaped the output equivalent noise unless something goes wrong like low phase margin. But I'm not sure if this low pass function is enough. Also, I have seen some DCDC switching regulator powering RF PA. Using pwm (pulse-width modulation) switching, there are harmonics tones at mulitple of switching frequencies. I suspect there is an "internal noise passive decoupling network" in RF PA to filter off this harmonics, not sure if the speculation is correct.
Thanks, Richard
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