Practical Issues in the Synthesis of Ternary Sequences
For engineers designing test signals for nonlinear systems, this work provides a flexible synthesis method with high harmonic suppression, though it is an incremental improvement over existing approaches.
The paper addresses practical issues in synthesizing ternary sequences for nonlinear system testing, specifically those suppressing harmonic multiples of two and three. It shows that non-uniform DAC levels degrade harmonic suppression and proposes randomized constrained sequences achieving ~100 dB suppression, validated via simulations and experiments.
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.