ADF4360-8_FM SNR specification

Question The output frequency is 88MHz-108MHz, channel spacing is 100KHz, reference frequency is 10MHz. For the loop filter, I would like to use the second passive configuration (3rd order) in the software ADISimPLL, loop bandwidth is 20Hz to 30Hz, the phase margin can be varied. I don't care about the lock time (I can accept 200mS lock time), but the FM SNR should be more than 60dB. From my simulation in the ADISimPLL, I can only get 58dB FM SNR, which is 2dB less than their requirement. Do you have any solutions to this problem? The reason for such a narrow loop bandwidth is because using it in the FM broadcast, and the audio frequency is 20Hz to 20KHz. And I like the high integration and the low cost of this part. Answer That will happen. The open loop VCO noise at this point according to simulation is - 60 dBc / Hz. The loop filter filters out any VCO noise inside this loop bandwidth. But if it is narrow, the VCO noise at 20 Hz (-60 dBc / Hz) will appear in the final system noise profile. Is it not possible to use a wider bandwidth? The synthesizer noise is very low inside the loop bandwidth, < -100 dBc. 25 kHz would be a very good choice of bandwidth.