LMX2594: Channel divider (Phase Noise)

Part Number: LMX2594

Hi team,

We arranged a product using LMX594.

When changing from VCO/4 to VCO/8, 20LOG(2) does not reduce by 6dB.

Please give me advice to improve.

                                        1kHz,  10kHz,  100kHz,  1MHz offset           

fout=VCO/2(5500MHz) : -102.2, -111.8, -113.4, -123.8 dBc/Hz

fout=VCO/4(2750MHz) : -109.9, -118.3, -119.3, -129.6 dBc/Hz

fout=VCO/8(1375MHz) : -113.4, -122.4, -124.1, -134.1 dBc/Hz

fout=VCO/16(687.5MHz) : -118.9 -128.1, -131.2, -141.2 dBc/Hz