An Accurate and Efficient Method for Eliminating the Requirement of Coherent Sampling in Multi-Tone Test

Multi-tone test is critical in evaluating the overall spectral performance of integrated circuits, especially when the whole signal bandwidth is filled with various frequency components. Coherent sampling is a major challenge for achieving accurate test results in multi-tone test, because it is difficult to simultaneously control all the signal tones precisely. Once coherent sampling is not satisfied, the spectral leakages and their overlap effect will deteriorate the spectral test results. In this paper, a new algorithm is proposed to eliminate the requirement of coherent sampling in multi-tone test. In this method, all the tones are simultaneously estimated with a two-step method which employs merely two FFTs and a few simply mathematical operations. Then new coherent data is reconstructed by replacing the noncoherent fundamentals with coherent tones, all the spectral leakages are removed. Extensive simulation results demonstrate that the proposed method can achieve the same testing accuracy as coherent sampling methods in arbitrary level of noncoherency. The proposed method greatly relaxes the test setup for multi-tone test, and hence the test cost can be reduced significantly.