Unwanted spurious noise in AD9914

Hi all,

We have designed DDS based board using IC AD9914. The application is to generate frequency range of 0.5-18 GHz.DDS board is generating frequencies from 0.4-1.6 GHz. There after doubling, amplification and switching is carried on to generate the final band of frequencies. there are 2 main problems am facing,

1) the IC AD9914 is getting heated very fast.

2) The unwanted spurious is very much high at the output of the DDS. As the chain up consists of amplifiers this is becoming still more worse.

3) We see sudden rise of noise floor and spurious and subsides immediately leaving the spurious level high.

Am attaching both the pics

The behaviour of the IC is intermittant

Please suggest and find the attachment.

attachments.zip
  • Hi,

    I apologize for the late response.

    I just have some few things I'd like to check:

    1. What is your SYSCLK?

    2. Kindly double check how your epad was connected. It should be connected to ground. The soldering quality also matters.

    3. Are the pictures you provided taken from the DDS output with the amplifier chain in power-down mode? Can you provide DDS outputs with the amplifier chain in (1) off mode, (2) power down mode and (3) enabled mode.

    Thanks.

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:07 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin