Sundance SMT364 - Manual (Page 16)

Version 1.0 Page 16 of 37 SMT364 User Manual
The following graphs gives the average FFT of sixteen 16K-FFTs processed after
capturing data from Channel B – The on-board sampling frequency set to 105 MHz –
A 21MHz sine signal is fed to the board. The test has been performed without any
input filter (which explains the second peak due to harmonics) at all and with a 35dBc
harmonic performance signal generator.
Figure 6 - FFT ADC Channel - On-board clock.
Similar results are obtained when using an external clock. It is recommended to use
a low-jitter clock and a filter on the ADC inputs. They indeed have a large input
bandwidth and therefore allow a high level of harmonics in.
The SMT6600 package, provided with the SMT364 contains a documentation dealing
with performance. It shows some captures and FFT graphs at different frequencies.