MIRE: A multitone identification and replacement method for multitone spectral test without requiring coherent sampling

Achieving coherent sampling has always been a great challenge in the spectral test of analog- and mixed-signal integrated circuits. It becomes more difficult in the multitone spectral test because all the fundamental tones should be precisely controlled to maintain stringent synchronization with the sampling clock simultaneously. If coherent sampling is not satisfied, severe spectral leakages and their overlap effect will lead to inaccurate test results. In this article, a new multitone identification and replacement method termed as MIRE is proposed to eliminate the requirement of coherent sampling in the multitone test. In the proposed method, the spectral leakages are eliminated by identifying and removing the noncoherent fundamentals with a two-step estimation which employs merely two-five fast Fourier transforms (FFTs) and a few simple arithmetical operations. Then, coherent fundamentals are calculated using a new closed-form formula, which accelerates the algorithm by avoiding complicated nonlinear iterations. Finally, new coherent data are reconstructed by replacing the noncoherent fundamentals with the coherent tones without changing any distortion component and noise information in the spectrum, and hence, accurate results are obtained. Extensive simulation results and measurement data obtained in the industry lab using high-precision ADCs demonstrate that the proposed method achieves the same accuracy as that of coherent sampling methods in the arbitrary level of noncoherency. Algorithm analysis and comparison study with other state-of-the-art multitone test methods also validate the robustness and efficiency of the proposed method. The presented method not only simplifies the multitone test setup but also provides potential solutions for multitone test in built-in self-test environment.