1. What is the function of "PWRDWN" switch on evaluation board?? No matter "PWRDWN" is pull high or pull low, ADRF6820 still working.
2. When using internal LO,
RFIN : 1900MHz, 0dBm, CW tone
REFIN : 153.6MHz, 0dBm, CW tone
LO set to 1890MHz (using customer evaluation software)
=> I+ port (we remove transformer T6 and resistors R38 & R42) see a ~38MHz ~358mVpp sinewave (oscilloscope is set to 1Mohm)..
When using external LO,
RFIN : same as above setting
LOIP : 1890MHz, 0dBm, CW tone
=> I+ port see a ~10MHz ~273mVpp sinewave (oscilloscope is set to 1Mohm).
Our question are:
a. When using internal LO, why the IQ sinewave frequency is not ~10MHz??
b. Why the amplitude level of I+ signal has large difference between using internal LO and external LO??
c. For external LO case, do you have a formula to calculate the I+ Vpp value with RF input power level??