If you're looking at the output noise, the reference sideband is not important. It is only needed if you need to compute a metric that depends upon knowing the correct gain between input and output. So input-referred noise, noise figure and noise factor require that.

The reference sideband essentially tells the simulator which frequency the expected input signal was supposed to be at. Since noise figure and noise factor are computed as the ratio of signal-to-noise at the input to signal-to-noise at the output, it needs to know the input frequency.

In pnoise/hbnoise/qpnoise you are sweeping the output frequency, and the input frequency will be |freqSweep+refSideBand*fundamental|. If this is multi-tone, then fundamental and refSideBand will be vectors (the fundamentals for each tone, and the multipliers for each tone respectively), and you'd sum that up to find the overall frequency shift. The UI has a "select from list" choice to make that easier to pick the right frequency range.

For an LNA, the reference sideband would generally be 0, and for a mixer (assuming no blocker), it would usually be 1 or -1 depending on whether your receiver is mixing from the upper or lower sideband respectively.

Regards,

Andrew.