ADS Envelope simulation spectrum wrong?

I use ADS Envelope simulation to simulate a PLL
this is the schematic:

(the VCO_dividedbyN is from the ADS PLL library)

I scope the frequency value from freq port, it is OK. But I check the VCO spectrum, it seems to be wrong:

the vtune is the VCO tunning voltage, the VCO_Freq_MHz = real(freq[0])
in the right is the VCO output and it's spectrum
spe=real(VCO[1])
spctrum=fs（VCO)

Why the frequency is OK, but the spectrum and time-domain signal is not right？