THE DUALITY OF LEAKAGE AND ALIASING AND IMPROVED DIGITAL SPECTRAL-ANALYSIS TECHNIQUES

When processing, recording, and analyzing continuous, analog signals o r functions with a digital computer, information is lost when the sign als are converted to digital form. When signals are sampled in one dom ain (time or frequency), the loss of information is characterized as a liasing in the other (frequency or time, respectively) domain. When a signal or function is truncated in one domain, the information loss is characterized as leakage in the other domain. It is shown that becaus e of the dual nature of leakage and aliasing, that leakage in one doma in reduces aliasing in the other domain and visa-versa. Examples of re ducing leakage or aliasing in each domain by the dual in the other dom ain are given to illustrate. Since current art has not used time alias ing to reduce frequency leakage previously, a time alias processor for this purpose is described. A flat-top window function with spectral l ineshape one frequency line in width is used in conjunction with the t ime alias processor to maintain leakage to within the nearest frequenc y line.