AD9911 modulation

Hello all,

I’m trying to realize amplitude modulation on the DDS AD9911. But I do something wrong. For example, I want to implement 2-Level Modulation without RU/RD. I write to the DDS:

CSR - 0x22

FR1  - 0x00,0x00,0x00

CFR - 0x40,0x03,0x03

CTW0 - 0x49,0xBA,0x5E,0x35   // 36 MHz if sysclk=125MHz

ACR - 0x00,0x13,0xFF

CTW1 - 0xFF,0xC0,0x00,0x00

I don’t see any amplitude on a spectrum analyzer, when P1=’0’ or P1=’1’.

When I write to the DDS:

CSR - 0x22

FR1  - 0x00,0x00,0x00

CFR - 0x00,0x03,0x02

CTW0 - 0x49,0xBA,0x5E,0x35   // 36 MHz if sysclk=125MHz

ACR - 0x00,0x13,0xFF

I see the amplitude with frequency of 36 MHz.

How I can implement a modulation?

regards,

Tola.

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