ADF7021 Transmit Signal Problem


I have a problem in transmission using ADF7021 modules, I use EVAL-ADF7021DBJZ boards.

I set up the transceiver with 2FSK RC Modulation, 24kbps data rate, 450Mhz channel frequency, 6KHz frequency deviation, etc.

Here is my detailed register configuration:

reg_0_data = 0x12B00000;
reg_1_data = 0x575011;
reg_2_data = 0x4275D0D2;
reg_3_data = 0x29903453;
reg_4_data = 0x80C6A694;
reg_5_data = 0x01915;
reg_6_data = 0x504C986;
reg_15_data = 0xE000F;

When I transmitted the data, there is an unwanted signal (like spurious) within 100MHz span, and the signal is getting more within time.

Here the picture, the signal I mentioned is marked in red.

Can you explain what is that signal? How that signal can be generated?