  Several issues related to the practical synthesis of ternary sequences with
specified spectra are addressed in this paper. Specifically, sequences with
harmonic multiples of two and three suppressed are studied, given their
relevance when testing and characterizing nonlinear systems. In particular, the
effect of non-uniform Digital to Analog Converter (DAC) levels on the spectral
properties of the generated signal is analyzed. It is analytically shown that
the DAC non-uniform levels result in degraded harmonic suppression performance.
Moreover, a new approach is proposed for designing ternary sequences, which is
flexible and can be adapted to suit different requirements. The resulting
sequences, denoted as randomized constrained sequences, are characterized
theoretically by deriving an analytical expression of the power spectral
density. Furthermore, they are extensively compared with three synthesis
approaches proposed in the literature. The approach is validated by numerical
simulations and experimental results, showing the potential to achieve harmonic
suppression performance of approximately 100 dB.
