ADF5902 can not output singal

i found ADF5092 output a correct singal,but the output power is very low about -40dBm, i modify the value of the TX amp cal code from 0 to 255,the out put power is always about -40dBm。 

Hi, 

You are right. Some of the registers are double buffered and requires R0 write to take effect. Therefore, R0 must be written after some of the registers.

I recommend writing the R0 after following the initialization sequence. 

TX AMP CAL CODE should be determined by the calibration sequence. 

If you are observing -40dBm, I recommend checking the termination and layout. Is there an AC Coupling capacitor to measurement device. 

Thanks,

Emrecan

You have to power up the TX in the Register 1 - the initialization sequence in the datasheet does that during calibration stage but then turns off both TX and neglect to turn them back on after the reset and before calibration.

Sorry its reg 0 not 1