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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.

Parents

1) I can't find Table 24 in my AD9864 datasheet,  the last table in my datasheet is table 19. Is there another version of 9864 datasheet? If yes could you send me one? Here is my datasheet version

2) My configuration is using 16 bit IQ data, and frame length is 48 bit. My SSICRB is 87 which means DW is 0(16 bit data).

Also my decimation factor is 900, with CLK=18MHz, so frame rate is 20KHz. I think this part should be ok, am I right?

3) I can't find table 24 to try it's setting but I can send you my IQ data captured also with the matlab graphic. It's good that you can help to analyze the data. I'll send you two groups of data, one is -30dBm 73.35MHz IF input, another one is -90dBm 73.35MHz IF input, both is modulated with 1KHz tone.

This is graphic for -30dBm:

zoom in for above one, can see it's 1k tone

Then this is the bad one of -90dBm input:

after zoom in it's almost noise.

I don't know how to add attachment here, so I'll copy one line data here and send the whole raw ssi data files to you by email. One line data includes 1.25ms IQ data, totally number is 1.25ms*20KHz = 25 pairs IQ data.

Below is raw ssi data for -90dBm. I want to say more about how to check the log. For example, the red one is 16 bit I data, but it's extended to 32 bit by log reason, so only the first 16 bit 000f is valid data. And the followed green one is 16 bit Q data, also be extended to 32 bit by log reason, so only the first 16 bit fffa is valid data.

000f 0000 fffa ffff 0022 0000 ffda ffff 001f 0000 fffe ffff 0033 0000 ffec ffff 002d 0000 ffee ffff 0018 0000 0023 0000 fff8 ffff 0039 0000 0009 0000 0018 0000 fffd ffff ffeb ffff ffec ffff 0004 0000 ffda ffff fffc ffff fff1 ffff ffc4 ffff fffe ffff ffeb ffff 0016 0000 fffb ffff 0013 0000 ffe4 ffff ffea ffff ffef ffff ffe3 ffff fff7 ffff fff2 ffff ffeb ffff ffdb ffff ffee ffff ffee ffff ffe6 ffff 0002 0000 fffe ffff fff9 ffff 000d 0000 fffc ffff 0018 0000 ffd2 ffff 000e 0000 ffce ffff 001f 0000

Below is raw ssi data for -30dBm.

eb2e ffff 06e6 0000 ea51 ffff fcb8 ffff edca ffff f3dc ffff f3ba ffff edf2 ffff f9e0 ffff eb19 ffff fe91 ffff ea54 ffff 0122 0000 ea64 ffff 019c 0000 ea7d ffff 006a 0000 ea7e ffff fdf9 ffff ea9e ffff fae2 ffff eb20 ffff f7e4 ffff ec1a ffff f59c ffff ed33 ffff f47f ffff edda ffff f4b6 ffff eda9 ffff f6a5 ffff ec86 ffff fad6 ffff eaf0 ffff 0150 0000 ea41 ffff 093b 0000 ec2a ffff 10be 0000 f1db ffff 1557 0000 fae7 ffff 1558 0000 0516 0000 111f 0000 0dac 0000 0aa3 0000 1316 0000 043b 0000 1560 0000

At last, is there any Hardware design that may cause this problem?

1) I can't find Table 24 in my AD9864 datasheet,  the last table in my datasheet is table 19. Is there another version of 9864 datasheet? If yes could you send me one? Here is my datasheet version

2) My configuration is using 16 bit IQ data, and frame length is 48 bit. My SSICRB is 87 which means DW is 0(16 bit data).

Also my decimation factor is 900, with CLK=18MHz, so frame rate is 20KHz. I think this part should be ok, am I right?

3) I can't find table 24 to try it's setting but I can send you my IQ data captured also with the matlab graphic. It's good that you can help to analyze the data. I'll send you two groups of data, one is -30dBm 73.35MHz IF input, another one is -90dBm 73.35MHz IF input, both is modulated with 1KHz tone.

This is graphic for -30dBm:

zoom in for above one, can see it's 1k tone

Then this is the bad one of -90dBm input:

after zoom in it's almost noise.

I don't know how to add attachment here, so I'll copy one line data here and send the whole raw ssi data files to you by email. One line data includes 1.25ms IQ data, totally number is 1.25ms*20KHz = 25 pairs IQ data.

Below is raw ssi data for -90dBm. I want to say more about how to check the log. For example, the red one is 16 bit I data, but it's extended to 32 bit by log reason, so only the first 16 bit 000f is valid data. And the followed green one is 16 bit Q data, also be extended to 32 bit by log reason, so only the first 16 bit fffa is valid data.

000f 0000 fffa ffff 0022 0000 ffda ffff 001f 0000 fffe ffff 0033 0000 ffec ffff 002d 0000 ffee ffff 0018 0000 0023 0000 fff8 ffff 0039 0000 0009 0000 0018 0000 fffd ffff ffeb ffff ffec ffff 0004 0000 ffda ffff fffc ffff fff1 ffff ffc4 ffff fffe ffff ffeb ffff 0016 0000 fffb ffff 0013 0000 ffe4 ffff ffea ffff ffef ffff ffe3 ffff fff7 ffff fff2 ffff ffeb ffff ffdb ffff ffee ffff ffee ffff ffe6 ffff 0002 0000 fffe ffff fff9 ffff 000d 0000 fffc ffff 0018 0000 ffd2 ffff 000e 0000 ffce ffff 001f 0000

Below is raw ssi data for -30dBm.

eb2e ffff 06e6 0000 ea51 ffff fcb8 ffff edca ffff f3dc ffff f3ba ffff edf2 ffff f9e0 ffff eb19 ffff fe91 ffff ea54 ffff 0122 0000 ea64 ffff 019c 0000 ea7d ffff 006a 0000 ea7e ffff fdf9 ffff ea9e ffff fae2 ffff eb20 ffff f7e4 ffff ec1a ffff f59c ffff ed33 ffff f47f ffff edda ffff f4b6 ffff eda9 ffff f6a5 ffff ec86 ffff fad6 ffff eaf0 ffff 0150 0000 ea41 ffff 093b 0000 ec2a ffff 10be 0000 f1db ffff 1557 0000 fae7 ffff 1558 0000 0516 0000 111f 0000 0dac 0000 0aa3 0000 1316 0000 043b 0000 1560 0000

At last, is there any Hardware design that may cause this problem?