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Driving ADL5375 IQ Modulator to 1dB compression

Question asked by arvabj on Feb 8, 2016
Latest reply on Feb 11, 2016 by THA

Hello,

 

i am using ADL5375-05 IQ modulator on my RF board. I am using the AD9122 DAC to drive the IQ baseband signals. I have the baseband interface circuit between AD9122 and ADL5375-05 similar to figure-4 of this app note:

http://www.analog.com/media/en/reference-design-documentation/reference-designs/CN0205.pdf

 

I am trying to figure out how to get maximum RF output power from the ADL5375-05. In the ADL5375 datasheet, in figure-6 the SSB output power close to 1 dB compression is several dBs more than the SSB power seen in figure-4, normal conditions. I see output power comparable to figure-4 by setting 20mA full-scale current from the AD9122 IQ outputs. But how do i drive the ADL5375-05 close to 1dB compression ? Do i just increase the full-scale current value of the AD9122 close to the maximum 31.7mA ? How does this affect the baseband ground referenced 50Ohm (and hence the 0.5V DC bias) and 100 Ohm shunt resistors values(and hence the voltage swing) ?

 

Thanks in advance !

AB

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