Evaluation of a poisson windowed test signal for pcm codecs

摘要

This project deals with the critical evaluation of a Poissonudwindowed test signal which was proposed for in-service andudproduction testing of filtered pulse code modulation systems. TheudPoisson windowed test signal has various advantages over theudexisting two test methods specified by the InternationaludConsultive Committee for Telephone and Telegraph (CCITT). Theudmain goals of the new test signal are to minimise the test timeudand to accommodate the send- and reel eve filters normally found inudcommunication systems.udThe evaluation process included the compilation of performanceudcurves of signal ,to noise ratio vs. signal level and gainudvariation vs. signal level. These curves were compiled byudsimulating the codec and filters on a digital computer andudprocessing the output data. Three sets of programs wereudThe results obtained revealed some fundamental limitations of theudproposed test signal. Using the basic properties of the Poissonudwindowed signal, an alternative test signal was proposed. It wasudthe single sided exponentially windowed sinusoidal which provedudto be suitable for the testing of filtered pulse code modulationudstems.