we have an issue with 3'rd harmonic level at ADRF6510 outputs. The ADRF6510 is driven from ADL5387 directly in DC-coupled mode as it was described in Rev.0 datasheet of ADRF6510. (Rev.A datasheet does not include that reference design any more). The input signal to ADRF6510 has the third harmonic ~52dBc while at the output of ADRF6510 we observe the 3'rd harmonic @ ~32dBc. The gain of ADRF6510 is fixed to 0dB. The FE gain switch is at 6dB.
The input of ADRF6510 runs at 0.5Vp-p as well as te output (as the gain is 0dB).
What could be the reason for increased 3'rd harmonic at the output of ADRF6510?
The output (both N and P separatelly) of ADRF6510 drive resistor based (150Ohm, 100Ohm) divider for ADC common mode voltage matching.