load_custom_data unwanted bw around LO frequency

Actually, I'm trying to make work the provided talise application without modifying the hw project.

I want to test the axi_dac_load_custom_data of the provided sine_lut_iq table. My LO is at 1GHz and I have used the "tx_bw100_ir122p88_rx_bw100_or122p88_orx_bw100_or122p88_dc122p88" profile. When I tried to see the output signal on the spectrum analyzer, I can see the 1.002 GHz frequency(LO + base signal) but I also have a 100MHz of Bw around the LO frequency which is undesirable for my future application (ScreenShot1)


I have tried to send DDS frequency using "axi_dac_dds_set_frequency" and it works percfectly. I have got a pic at LO+dds frequency and 100mV peak-2peak of amplitude since I have scaled the signal with 100mUnits (axi_dac_dds_set_scale(dac, ((ch*2)+1), 100*1000)) (ScreenShot2) 


When I put the scale on more than 500mUnits axi_dac_dds_set_scale(dac, ((ch*2)+1), 500*1000), some harmonics are shown on my spectrum analyzer (ScreenShot3)


I tried so to decrease the amplitude of the sine_lut_iq signal and code it on 16 bits and then on 12 bits but unfortunately I have got the same signal amplitude = 60mV and some harmonics around the LO frequency. What is the relation in number between the number of bits used for the sine_lut_iq and the signal amplitude. I could'nt confirm that the signal amplitude saturates the amplifier and so causes the harmonics. Could you please explain me these phenomenas.