| FFT-based tests (e.g. gain, distortion, SNR, etc.) from a device-under-test (DUT) exhibit normal distributions when the measurement is repeated many times. Hence, a statistical approach to evaluate the accuracy of these measurements is traditionally applied. The noise in a DSP-based mixed-signal test system severely limits its measurement accuracy. Moreover, in high-speed sampled-channel applications the jitter-induced noise from the DUT and test equipment can severely impede accurate measurements.;An integrated mixed-signal test core was implemented in TSMC's 0.18 mum mixed-signal process. Experimental results obtained from the mixed-signal integrated test core validate the proposed digitizer architecture and post processing technique. Bias errors were successfully removed and measurement variance was improved by a factor of 5.;A new digitizer architecture and post-processing methodology is proposed to increase the measurement accuracy of the DUT and the test equipment. An optimal digitizer design is presented which removes any measurement bias due to noise and greatly improves measurement repeatability. Most importantly, the presented system improves accuracy in the same test time as any conventional test. |
