aaron_do wrote on Sep 1st, 2010, 11:36pm:1) I could use a vector signal generator which generates both tones from a single output.
Yes, you can do it very easily.
aaron_do wrote on Sep 1st, 2010, 11:36pm:I'm not sure how the two tones are generated,
vp1953 wrote on Sep 3rd, 2010, 2:59pm:But i think some of the newer equipment can generate two tones simultaneously,
Almost all signal generators can generate two tones as
DSB-AM with suppressed carrier, as far as tone separation is within 100kHz.
But high performance signal generators which have wide-modulation ability are required for generation of wide separated two tones.
aaron_do wrote on Sep 1st, 2010, 11:36pm:but each tone is spread in frequency such that the signal looks much like a wideband FSK signal.
Don't use FSK.IP3 is due to AM/AM characteristics.
However FSK signal is a constant envelope signal.
See
http://www.designers-guide.org/Forum/YaBB.pl?num=1190971685/9#9aaron_do wrote on Sep 1st, 2010, 11:36pm:2) I could use two separate signal generators and combine the signals using a coupler.
Should I expect any significant difference in the measurements from the two methods?
Currently separtion of two tones is at most MHz order even if high performance signal generators are used as method-(1).
And suppression of carrier could be not good.
Merit of method-(1) is that we don't have to adjust amplitude level of two tones.
aaron_do wrote on Sep 1st, 2010, 11:36pm:For the simulations, I did not simulate the IIP3 of the LNA and mixers,
just the low-pass filters (I simulated the LNA IIP3 separately).
I estimated the overall IIP3 by subtracting the LNA+mixer gain from the filter IIP3.
Your estimation of IIP3 may be not appropriate.
Study signal level budget for total cascaded system.
Here you have to take care of filtering characteristics of each block as well as IM3 of each block.