What is the difference between VCO， VCO[1]， real(VCO) in ADS?

In the ADS envelope simulation, assuming the complex signal is VCO
I use the following:
mag(VCO)
mag(VCO[1])
the output are not the same
so anyone can tell me what is the difference between VCO, VCO[1], real(VCO)

If VCO is a complex signal vector then by simple math mag(VCO) is the instantanious magnitude of the complex signal vector and real(VCO) is the real part of the complex signal vector.

Now if you were to look at the spectrum of the complex signal VCO you would see several tunes, each being a vector at the appropriate frequency such that

VCO = VCO(dc) + VCO(freq) + VCO(2*freq) + VCO(3*freq) + ... + VCO(N*freq)

In this case VCO[1] is therefore the first frequency tone in that series, VCO(freq).

So mag(VCO) will not equal mag(VCO[1]). VCO is the whole complex signal but VCO[1] is the fundimantal tone that is part of VCO.

Finally I understand... Thank you
And I have another problem with the spectrum, please give me a hand in the Thread:ADS Envelope simulation spectrum wrong?
Thanks

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