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?
The overshoot is due to reactive circuit (L C network). L acts as open circuit and C acts as a short circuit at the time of switching on/off
Transmitter overshoot is due to transient response of biasing circuits as well as input and output matching circuits.
additionally there is thermal effect involved Typically Gm of transistors is higher when device temperature is lower...
Dear Donghyun Youn , how are you ?
It is interesting to think about the question as a problem of excitation of an order second system. I am talking about the output matching network composed by the inductor and capacitor. I suggested you analyzed the pole of the output matching, more specifically, the real part. Is it possible to reduce this value ?? Can you use another matching network ??
Best Regards
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