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IP3 measurement of ADRF6516

Question asked by tmain on Aug 14, 2014
Latest reply on Aug 18, 2014 by jdobler

I am trying to verify the performance of a simple line-up ADL5380 eval board followed by ADRF6516 VGA/LPF. I added 632 differential impedance to ADRF6516 which makes it  454 Ohm with 1600 input impedance of actual IC. The ADRF6516 is loaded with 8: 1 transformer.  Also I removed the output transformer that is on the output of ADL5380.  I measured gain, IIP3, NF at 900 MHz for various VGA configuration and Vgain control voltage. I also checked the ADL5380 separately- everything checks out, NF and IIP3. But the IIP3 of the line-up should be close to 10 dBm not + 3.8 dBm – assuming the OIP3 of VGA is at 49 dBm, so the input should be at +21 dBm and that I/Q demod contributes very little since it is over 29 dBm?

Any thoughts would be appreciated...