Simulink Spectrum analyzer plot not correct

Hello,

I did a small model with a Bernoulli binary generator and spectrum analyzer. sample rate of binary generator is 1/6000. I am getting flat spikes from -3K to +3K frequencies.Output datatype is boolean. seed is 0. Probability of zero is 0.5. I am supposed to get a curved structure like an inverted U between -3 to +3. Why am I not getting it? Is there any other source with output binary bits.

Please help.

Thanks in advance.

With Regards Shalini