On our custom board we are trying to generate a single tone.
TxTSG with NCO output works fine.
The configuration is as follows:
- CGEN is set to 200MHz
- Interpolation ratio is set to 1
- FCLK1 is 200MHz and DIQ is at 400MSps
- 12bit LUT inside FPGA generates single tone at set frequency while sampling at 100MHz.
- I assume DAC sampling rate is independent of interpolation ratio and is decided by CGEN (in this case each channel of the DAC is sampling at 200MSps).
- SXT is configured to generate 2.25GHz
- Both I and Q are being fed the same single tone (not quadrature)
This is the output for 10MHz being generated
This is the output for 11.5MHz
Scaling my LUT output doesn’t change the output level at all.
So bit shifting right by one bit should decrease the output by 6dB, but the output remains fixed.
data_I <= LUT_I(11) & LUT_I(11) & LUT_I(11) & LUT_I(11) & LUT_I(11 downto 4);
gives the same output as
data_I <= LUT_I(11 downto 0);
(the LUT is full scale).
In fact for the 10MHz case feeding only the MSB also produced the same spectrum.
i.e., data_I <= (others => LUT_I(11));
Thank you for looking into my issues,