about the beat freqency in pss simulation

[knightgreen]

hi everybody, i want to simulate the Tuning Sensitivity and Linearity of a vco, but i don't knowhow to set the beat frequency.it seems that the fundamental frequency changes when i changes thebeat frequency.how to set the correct beat frequency in pss simulation?
thanks in advance!

 

[safwatonline]

i am not sure but isn't the beat freq. of osc. is the oscillation freq.