you mentioned that you getting 28% eff. how about power? are you getting good power? if yes, the optimum load impedance is for power and not efficiency. take note that optimum load impedance for power may not give good efficiency. a PA designer usually will choose impedance which give optimum power and efficiency. you can verify this with TI. good luck.
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Hello pragash, thanks for your input. 28% eff , RF Module (RFIC MAX RF POWER LEVEL + LDMOS OUT) 27dBm @ 6V 300mA; cc1120 will output +15dBm with opt load. and the LDMOS will give about 15dB gain<with Zopt load>. ... with the same bias condiction, I want make it output power up to 28.5dBm +;
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i think you have to use optimum load impedance given in the datasheet. just make sure you using bias condition for optimum load impedance for accuracy.
the other method is to do loadpull measurement for the device. Its require you to do TRL fixture for cc1120 for calibration and loadpull test setup. if you dont have it, you have to use datasheet impedance.
another way is to ask TI but i believe that they will give you the same value as in datasheet.
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LDMOS input match to CC1120 Zopt load and then the LDMOS Zopt load will be change.... so if I tune the PA deivce Zout,,, PA input impedance will be change so CC1120 PA in Z load will be change...
I think between CC1120<-->LDMOS ,need to do gain match.
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