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I am implementing power amp. with 16-QAM. Because of issue on power consumption, I am using time division duplex (TDD). By TDD, the power amp. turns off if the carrier wave is not needed and vice versa.

As represented in the figure, PLL makes 4 output signals P0~P270 with 90 degrees difference each. When PA turns off, the switch between PLL and PA disables to block AC signals.

Here is the issue:

There exist some overshoots when the power amp. turns on by TDD.

Does anyone experienced this overshoot when the transmitter turns on? What would be the reason?

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Donghyun Youn
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  • You need to show the exact and precise circuit you have used and not some prettified version because how can anyone say what happens without full details? – Andy aka Sep 02 '20 at 19:03
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    Check the supply rail with TX off and turning on. How well is it regulated? –  Sep 02 '20 at 19:19
  • Can you capture a waveform of those "overshoots" and add it to your question? Can you share your exact circuit? – eeintech Sep 04 '20 at 03:13

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