Marc, Michael, Yuhang

We checked the resistor and noise spectrum of several points on DDS board.

Brief introduction of DDS board configuration: Power supply (24V) > voltage regulator (1.8V goes to generate signal, 3.3V goes to power up chip/USB) > 1.8V > AVDD point> DDS process > filter-in point > 200MHz low pass filter > filter-out point > to be used

Figure 1~3 show resistors from ground to:

AVDD: 0.83kOhm

filter-in: very high (seems to be not connected)

filter-out: 2.7Ohm

Figure 4 shows the noise spectrum of those points and power supply.

We could see that power supply is clean. But once DDS board is connected, almost every point inside DDS board show ~20kHz peaks.