Recommended DAC configuration#
In order to output frequencies up to 9 GHz, Presto uses a digital-mixing stage just before the
digital-to-analog converter (DAC).
dac_mode and DAC sampling rate
dac_fsample are two
parameters one needs to choose depending on the output frequency.
A helper function
utils.recommended_dac_config() can recommend the optimal configuration: we
just pass the frequency we want to output and it will return the suggested
dac_mode, dac_fsample = recommended_dac_config(5.2e9)
with pulsed.Pulsed( address=presto_address, port=presto_port, ext_ref_clk=ext_ref_clk, adc_mode=AdcMode.Mixed, adc_fsample=AdcFSample.G2, dac_mode=dac_mode, dac_fsample=dac_fsample, ) as pls:
The function can also print all DAC configurations compatible with the requested frequency, and calculate the frequency of the nearest spurious signals that are generated due to digital mixing. Further, it suggests an appropriate analog filter that can be connected to the output of Presto to suppress these spurs:
dac_mode, dac_fsample = recommended_dac_config(5.2e9, print_all=True)
Valid DAC configurations for signal at 5200.0 MHz: * Mixed42-G8 (score 1680): - low-frequency spur: 2800.0 MHz - high-frequency spur: 10800.0 MHz - compatible band-pass filters: ['VBFZ-5500-S+', 'ZBSS-6G-S+', 'ZVBP-5G-S+'] * Mixed02-G6 (score 1173): - low-frequency spur: 800.0 MHz - high-frequency spur: 6800.0 MHz - compatible band-pass filters: ['ZVBP-5G-S+']
recommended_dac_config() can plot all of the recommended combinations of DAC
sampling rates and modes (bands of blue, orange and green), the targeted frequency, and nearest
spurs in red:
dac_mode, dac_fsample = recommended_dac_config(5.2e9, plot=True)
Depending on your application, the recommended settings might not be the optimal ones. In this case, you are always able to manually set all the configuration parameters.