Hi All,
i want to calculate the output power(dBm) and noise figure of DAC for my RF chain budget. However i could not succeed it. Could you please define how should i define for a 400 MHz BW?
Regards
Hello,
Unfortunately the AD9176 datasheet does not provide a frequency response sweep (similar to AD9177 datasheet showing below) for a swept full-scale 0 dBFS digital sine wave for a specified balun/layout as shown below. The AD9176 is likely to be similar (but not exactly the same) as the AD9177 since they similar 28 nm DAC cores albeit on different laminate designs. If we assume that they are the same than one could extract the full-scale power output off of this curve at the particular frequency of interest (for the given sample rate). For noise figure, one can use figure 33 of the datasheet to determine the NSD in dBm/Hz (at 10% offset freq offset where close-in phase noise is not included). The difference between this number and -174 dBm/Hz (at 25 C) will give you the noise figure. For example, if the NSD measures to be -160 dBm/Hz, than the NF is 14 dB.
It should be noted that the increasing NSD with output frequency is due to jitter on the clock hence the NSD at 10% offset will be sensitive to the output frequency as well as type of waveform being reconstructed where a full-scale sin wave at 0 dBFS represents worse case being full-scale with a crest factor of 3 dB. A sinewave of having back-off from full-scale will have a lower jitter contribution hence NF dependency on the frequency output, the waveform being reconstructed as well as wideband phase noise characteristics of input clock.
Hello,
Unfortunately the AD9176 datasheet does not provide a frequency response sweep (similar to AD9177 datasheet showing below) for a swept full-scale 0 dBFS digital sine wave for a specified balun/layout as shown below. The AD9176 is likely to be similar (but not exactly the same) as the AD9177 since they similar 28 nm DAC cores albeit on different laminate designs. If we assume that they are the same than one could extract the full-scale power output off of this curve at the particular frequency of interest (for the given sample rate). For noise figure, one can use figure 33 of the datasheet to determine the NSD in dBm/Hz (at 10% offset freq offset where close-in phase noise is not included). The difference between this number and -174 dBm/Hz (at 25 C) will give you the noise figure. For example, if the NSD measures to be -160 dBm/Hz, than the NF is 14 dB.
It should be noted that the increasing NSD with output frequency is due to jitter on the clock hence the NSD at 10% offset will be sensitive to the output frequency as well as type of waveform being reconstructed where a full-scale sin wave at 0 dBFS represents worse case being full-scale with a crest factor of 3 dB. A sinewave of having back-off from full-scale will have a lower jitter contribution hence NF dependency on the frequency output, the waveform being reconstructed as well as wideband phase noise characteristics of input clock.
