Other Parts Discussed in Thread: AFE7070
Tool/software: WEBENCH® Design Tools
Hi:
When we use your afe7071 IQ modulation chip, we found that: there is a strong harmonic component in the integral frequency doubling rate of DAC-CLK clock of the chip, especially twice, for example, when using 64MHZ clock input, the highest spurious appears at 128MHz, when using 40MHz, The highest point is 80MHz, at the beginning, we suspected that there was a problem in our PCB design, But after many times of troubleshooting, PCB revision and comparison with the same conditions of development board provided by your company, Finally, we confirm that as long as the DAC clock of the chip starts to work, spurious signals will appear on the output; the same phenomenon will be observed when using your company's demo board alone. At the same time, we compared the afe7070 with the afe7071, and found that the same problem exists in the afe7070, It's just the level is lower. The related oscillogram will be attached!
Please help to analyze and solve as soon as possible, thank you!
Fig. 1 compares the waveforms of afe7070 and afe7071 by using your demo board. The clock is an external reference clock;
Figure 2 shows the use of demo board, the chip is afe7070, 10MHz is provided by demo board, and VCO is provided by external;
Figure 3 shows the spectrum measured by the board designed by desin. The chip is afe7071;
