I need to simulate an entire receiver front end with BPF and VCO. I am not sure how to perform PSS and PAC and other harmonic
balance analyses without the LO port for the mixer. As you may remember while running
PSS we generally find the steady state response by specifying the LO
port to be the Large signal but such a port does not exist as I am
using a VCO. Can you please respond with simulation setups or point me to a dcoument that would contain the same?
If the only large signal is the VCO (i.e. you have no other large signal driven inputs), then you would simulate the mixer just as you would if you were simulating an oscillator - i.e. tell PSS that it's an oscillator and point at the output of the oscillator. Then you can have a small-signal input to the mixer, and look at the transfer function to the output of the mixer.
If you want to have a large signal (driven) signal to the mixer, to investigate (say) distortion of the input signal through the mixer, in the presence of the VCO, then you can also do this with the "hb" analysis (you need to use "hb" rather than "pss" in "harmonic balance" mode). The hb analysis allows what we call semi-autonomous analysis. If you pick this, turn on the "oscillator" checkbox and select the oscillator outputs as usual. Then for tone 1, specify the estimate of the oscillator frequency, and number of harmonics, and then specify the frequency of the other driven signals. Hopefully the use model is reasonably clear...
If this doesn't make sense, please ensure you include the subversion of icfb/virtuoso you're using (Help->About... in the CIW), and the subversion of spectre you're using (this will appear in the spectre.out displayed in ADE, or by typing "spectre -W" on the UNIX command line).
In reply to Andrew Beckett:
Thank you Andrew. Your reply made a lot of sense.
I have another question about the output I get from my VCO. It is about the different results I get from different analyses. My goal is to design a VCO operating at 2.45GHz. When I do a transient and use the frequency function in the calculator I get a freq value almost equal to 2.45 GHz. On the other hand if I do a PSS (with the oscillator box checked) and calculate the harmonic frequency I get 2.47GHz. There is a discrepancy of about 20MHz which makes a lot of difference when it comes to desigining a direct conversion/ Low-IF receiver. Which result do you think is more reliable ? The one from the calculator (2.45GHz) or the one from PSS (2.47GHz).