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Hi,
We are evaluating the LMX2572 EVM for our application to generate a reliable LO frequency (400 M to 6GHz) to be fed into the mixer.
The datasheet spec w.r.t harmonic power seems good and acceptable (worst case -20 dBc for second harmonic and -13dBc for third harmonic).
However, when we measure the EVM performance across the range 500M to 3GHz (usingspectrum analyzer limited to 6GHz), we see that the harmonic performance is very poor. Below is the table of measured results. Also attached are some of the plots. Can you please let me know how to achieve datasheet spec in the range 500M to 6GHz?
Settings: Default configuration as explained in the user guide. 100MHz single ended LVPECL clock to LMX2572 EVM. PLL configured in integer mode.
Can anyone plese help me understand why the harmonic performance is very bad on the EVM, esp. for 2nd harmonic which is nearly 10dB worse than DS spec ?
| fout | 2nd Harmonic (dBc) | 3rd Harmonic (dBc) |
| 250 MHz | -10 dBc | -11dBc |
| 500 MHz | -9dBc | -16dBc |
| 1 GHz | -10dBc | -8dBc |
| 1.5 GHz | -13dBc | -8dBc |
| Expected worse case as per DS : | -20dBc | -13dBc |
