[Questions] ADS simulation on FM TX circuit

Hi all,

i'm draw the this circuit using ADS, refering to the schemetics. I've simulated it and everything is working fine, the frequency changes when the input voltage changes. However, I have a few questions about the circuit.

1, What"s the function of C8 and R1 (base of the oscillator)? Is it just a coupling capacitor?

2, How can I show that the frequency changes with voltage (in one graph, X=freq, Y=voltage). Currently, i change the value of the input voltage and simulate the whole thing again. I try using parameter sweep but have error in simulation. Can someone advice me?

Thanks in advance

Alex