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ADL5375-05 harmonics

Hello,

I'm testing ADL5375-05 modulator on ADL5375-05EP EVALZ evaluation board and I'm getting higher order harmonics significantly higher then specified.

The test I did is replica of the datasheet test at 2.15 GHz and 3.5 GHz. The LO is single ended and power is set to 0 dBm and LO source is filtered with low pass filter. BB signal is 1 MHz  sine wave with 1 Vp-p differentially. Baseband common mode voltage 0.5 V. LO leakage and image cancelation don't help.

The results I'm getting are:

at 2.125 GHz 2nd harmonic -40 dBc, 3rd order harmonic -14 dBc (datasheet spec are -75 dBc and -55 dBc)

at 3.5 GHz second harmonic -20 dBc, 3rd harmonic -20 dBc (datasheet spec are -55 dBc and -50 dBc)   

Can you please help me to sort this problem?

Thank you,

Dragan