Accurate measurement of multi-tone power ratio (MTPR) of ADSL devices using low cost testers

Measurement of multi-tone power ratio (MTPR) on the transmitter output of a central office ADSL analog front-end device (AFE) poses stringent requirements on the linearity of the ATE digitizer. Cost of the ATE digitizer that can perform this test in a specification compliant manner is prohibitively high. In this paper, a test technique to perform TX MTPR test on a central office ADSL device using low-cost automatic test equipment (ATE) is proposed. The proposed technique is based on adding optimum dither noise to the output of the DUT, to improve the performance of the low cost ATE digitizer. The dither reduces the distortion caused by the static errors in the ATE digitizer by randomizing these nonlinear errors. Results obtained using the proposed method on ASDL AFE devices show an improvement of ∼7dB in MTPR measurement with very good repeatability.