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Why AD9864 output is noise when input IF signal is -90dBm

Our product is using AD9864, by out test, when the input IF signal with level of -90dBm directly into AD9864, and the DSP capture AD9864 SSI output IQ data then draw it with Matlab, the data is almost noise, we can't see valid signal. For -70dBm input or -30dBm input, the IQ data looks ok.

So, what's the possible reason for my problem, hardware or AD9864 configuration issue? Could anyone help me? Also I want to know what's the smallest input level that AD9864 can accept.

Here is my AD9864 register setting. And my IF input freq is 73.35MHz, LO freq is 71.1MHz.

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  • Hi PMH,

    'The AD9864 provides constant gain in the region where the AGC is not active.' AGC is disabled in my setting, AGCG is also set to "0", so do you know the exact value of the constant gain?

    BTW, with above setting, when input IF signal is about -40dbm, the ATTN and SSI value on SSI frame is about 0x0009; with -50dbm input, the value is 0x0002; with -60dbm input, the value is 0x0000. Do you know how to convert these value to the true IF input power?

    Thanks.

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  • Hi PMH,

    'The AD9864 provides constant gain in the region where the AGC is not active.' AGC is disabled in my setting, AGCG is also set to "0", so do you know the exact value of the constant gain?

    BTW, with above setting, when input IF signal is about -40dbm, the ATTN and SSI value on SSI frame is about 0x0009; with -50dbm input, the value is 0x0002; with -60dbm input, the value is 0x0000. Do you know how to convert these value to the true IF input power?

    Thanks.

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