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AFE5808A: CW noise

Part Number: AFE5808A
Other Parts Discussed in Thread: AFE5808

Hello,

Our customer  used AFE5808 for ultrasonic imaging to simulate the CW function, and his design is referred to TIDA-01351.

He used CWx16 mode, and used 2Mhz square wave transmitter frequency as excited ultrasonic probe, so the 1x clock is 2Mhz LVDS clock, 16X clock is 32Mhz LVDS clock. and the signal is passed through CW mixer-----summing amplifier and then output IQ, then it is amplified----filter----ADC sample.

But now he met the question is that when sampled by ADC, there is obviously noise at 2.7Khz frequency. Please refer to the FFT after ADC sampled. 

In addition, Does the 2Mhz transmitter frequency need to sync with 1x and 16x clock? Or why it would appear noise at 2.7Khz?

 

  

Best regards

Kailyn