Accurate Spectral Testing with Non-coherent Sampling for Multi-Tone Test
Multi-tone test has gained popularity among nowadays test methods, as it offers flexibility in characterizing systems whose
nonlinearities vary over signal frequency, which can be impractical to test using single tone test. For multi-tone, noncoherent sampling is the major issue in performing accurate spectral testing, since precise control over each of the test tone frequency is very challenging to achieve, and such control may not be possible for on-chip testing. In this paper, a new method is proposed to resolve such issue. Based on closed form initial estimation of non-coherent fundamentals, more accurate estimation of non-coherent fundamentals can be obtained, and by replacing non-coherent fundamentals with coherent ones, accurate spectral results is achieved. The accuracy and robustness of proposed method is examined extensively by simulation and measurement results, and comparisons were made with different methods. Combined with its high accuracy, robustness and computational efficiency, the proposed method can be implemented for high precision spectral testing, which relaxes the requirement of coherent sampling for multi-tone test. In addition, it is also suitable for accurate signal spectral analysis when coherent sampling is not achieved.