Two-Tone Harmonic Balance Noise Settings: "Relative Harmonic" and "Reference Side-Band"

Two definitions:

1. Relative Harmonic - this is used to make specifying the output sweep easier, and is mostly used with oscillators because the precise frequencies are not known. With an hbnoise analysis, you specify the output frequency band across which you are measuring the noise. If this is a relative harmonic, then it means that you add n*hbFund to the sweep frequencies to specify the actual output frequency, or n1*hbFund1+n2*hbFund2... if there is a vector [n1 n2]. If it's a receiver then this would normally be 0 (or [0 0]) so you might just as well use absolute frequencies - with an oscillator it would normally be 1 or if there's an interferer in a semiautonomous HB it might be [1 0] since your sweep is probably still relative to the oscillator frequency.
2. Reference Sideband - this is used to determine the frequency that the input signal is at. Given that noise analyses compute the output-referred noise, if you want to compute noise figure, noise factor or input-referred noise, then it needs to know where the signal would come from so that it knows the appropriate gain. If you have just the LO in a mixer and it's a receiver (so the output noise is at baseband) then you'd add n*hbFund to that output frequency sweep to determine the input frequency - hence it would be -1 if the signal is at the lower sideband or +1 if the upper sideband. If there are multiple large tones, then this is a vector n1*hbFund1+n2*hbFund2 etc to add.

Now, most of the time if you are simulating the noise in a mixer, you wouldn't have a large-signal input (the RF input) at the same time because then you are measuring the noise in the presence of a large signal. That only typically matters if the signal is large enough to saturate the input and cause compression which might alter its noise performance. If you're trying to simulate with the effect of a blocker, then yes, you might have a large signal at the RF input - but the reference sideband wouldn't take that into account (you are not dependent on mixing with this signal to get the small-signal input from the input to the output of the mixer) - so the reference sideband would then be [-1 0] or [1 0].

I'm a bit confused because you said that the NF numbers are close but then you said they are too far off.

Anyway, hopefully this helps clarify how this works!

Andrew

Two definitions:

1. Relative Harmonic - this is used to make specifying the output sweep easier, and is mostly used with oscillators because the precise frequencies are not known. With an hbnoise analysis, you specify the output frequency band across which you are measuring the noise. If this is a relative harmonic, then it means that you add n*hbFund to the sweep frequencies to specify the actual output frequency, or n1*hbFund1+n2*hbFund2... if there is a vector [n1 n2]. If it's a receiver then this would normally be 0 (or [0 0]) so you might just as well use absolute frequencies - with an oscillator it would normally be 1 or if there's an interferer in a semiautonomous HB it might be [1 0] since your sweep is probably still relative to the oscillator frequency.
2. Reference Sideband - this is used to determine the frequency that the input signal is at. Given that noise analyses compute the output-referred noise, if you want to compute noise figure, noise factor or input-referred noise, then it needs to know where the signal would come from so that it knows the appropriate gain. If you have just the LO in a mixer and it's a receiver (so the output noise is at baseband) then you'd add n*hbFund to that output frequency sweep to determine the input frequency - hence it would be -1 if the signal is at the lower sideband or +1 if the upper sideband. If there are multiple large tones, then this is a vector n1*hbFund1+n2*hbFund2 etc to add.

Now, most of the time if you are simulating the noise in a mixer, you wouldn't have a large-signal input (the RF input) at the same time because then you are measuring the noise in the presence of a large signal. That only typically matters if the signal is large enough to saturate the input and cause compression which might alter its noise performance. If you're trying to simulate with the effect of a blocker, then yes, you might have a large signal at the RF input - but the reference sideband wouldn't take that into account (you are not dependent on mixing with this signal to get the small-signal input from the input to the output of the mixer) - so the reference sideband would then be [-1 0] or [1 0].

I'm a bit confused because you said that the NF numbers are close but then you said they are too far off.

Anyway, hopefully this helps clarify how this works!

Andrew