Post Go back to editing

ADL5535 1PdB - 1dB Compression Point Unterstanding

Hi Folks,

please could you help me to explain the fact, that the ADL5535 has a higher 1dB compression point than the power supply allows?


Example:

1dB P1 = 18.6dB as lowest in statistic, according to Fig.11. of the datasheet.

 

18.6dB is 72.44mW into a 50 Ohm load.

U = SQRT (P*R) = SQRT (72.44mW * 50) = 1.9Vrms

Upeak = 1.9Vrms * sqrt(2) = 2.69V


To run Upeak-peak the Voltage swing is: 2 * 2.69V = 5.38V.

This should be the voltage on the 50Ohm termination.

If we consider the internal driver has a 50Ohm series termination, the driving voltage must have 10.77V. Considering no extra headrom for the transistors to drive the load.


How can the outputpowerlevel of at least 18.6dB be explained?

Is the datasheet correct?


Thanks.


 

Parents
  • For clarification, I should point out that a conjugate match based on the S-parameters will minimize reflected power, but it will generally not maximize power delivered to the load. Steve Cripps' "RF Power Amplifiers for Wireless Communications, 2nd Ed." has an excellent discussion of real world matching of power amplifiers (see Preface and  P. 19). If one assumes that "internally matched to 50 ohms" implies matching for minimum reflected power, then it also seems to imply that maximum power is not delivered into a 50 ohm load and that another load may be used for maximum power measurements. The basic question here is: What is the load used for P1dB measurements?

Reply
  • For clarification, I should point out that a conjugate match based on the S-parameters will minimize reflected power, but it will generally not maximize power delivered to the load. Steve Cripps' "RF Power Amplifiers for Wireless Communications, 2nd Ed." has an excellent discussion of real world matching of power amplifiers (see Preface and  P. 19). If one assumes that "internally matched to 50 ohms" implies matching for minimum reflected power, then it also seems to imply that maximum power is not delivered into a 50 ohm load and that another load may be used for maximum power measurements. The basic question here is: What is the load used for P1dB measurements?

Children
No Data