Shortened square wave waveforms in synchronous signal processing

Measurement of impedance is by definition conducted with sinusoidal waveforms. In many practical cases sinusoidal signals are replaced with suitable approximations. It could be square wave, piecewise continues approximation of the sinusoid or other suitably chosen waveform. In all cases care must be taken to avoid errors introduced by higher harmonics. Square wave signals are easy to generate and energy efficiency is high. Their resulting spectra however are most unfavorable. Piecewise continues approximations of the sinusoid are harder to generate and are sensitive to level errors. Well-known alternative is the three level shortened square wave. While it improves measurement accuracy compared to simple square wave, spectral content leaves room for improvement. By introducing more equally spaced levels, higher harmonics can be reduced. This multilevel signal is still easy to generate digitally and enables simple digital processing involving only additions and shifting.