Since in integrated circuits on chips, the physical size of components including transmission lines is much smaller than the wavelength of frequencies around 1-3 GHz, why do we revert to microwave analysis: S parameters, reflection coefficients, the use of Smith chart, etc...? Why can't we just use analog circuit analysis exclusively? i.e. voltages and currents?
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... around 1-3 GHz, why do we revert to microwave analysis: S parameters, reflection coefficients, the use of Smith chart, etc...? Why can't we just use analog circuit analysis exclusively? i.e. voltages and currents?
Because to use voltages and currents, you have to measure voltages and currents, and that's very difficult at 3 GHz, at least to do it in a controlled and repeatable way. That's why we measure waves in a transmission line system, it's controlled and repeatable.
Once you're measuring waves, it's sensible to stick with parameters that work with those measurements, S parameters, reflection coefficients etc, rather than transforming them to voltages and currents, which would be possible, but would be a waste of effort.
Even if components are small, their electrical delay means that to cascade them, we still need to take account of their full set of S-parameters.
