Editing Aliasing (section)

== Historical usage ==

Historically the term ''aliasing'' evolved from radio engineering because of the action of [[superheterodyne receiver]]s. When the receiver shifts multiple signals down to lower frequencies, from [[Radio frequency|RF]] to [[Intermediate frequency|IF]] by [[Heterodyne|heterodyning]], an unwanted signal, from an RF frequency equally far from the [[local oscillator]] (LO) frequency as the desired signal, but on the wrong side of the LO, can end up at the same IF frequency as the wanted one. If it is strong enough it can interfere with reception of the desired signal. This unwanted signal is known as an ''image'' or ''alias'' of the desired signal.

The first written use of the terms "alias" and "aliasing" in signal processing appears to be in a 1949 unpublished Bell Laboratories technical memorandum<ref name=Tukey-Hamming/> by [[John Tukey]] and [[Richard Hamming]]. That paper includes an example of frequency aliasing dating back to 1922. The first ''published'' use of the term "aliasing" in this context is due to [[Ralph Beebe Blackman|Blackman]] and Tukey in 1958.<ref name=blackman&tukey-Bell/>  In their preface to the Dover reprint<ref name=blackman&tukey-Dover/>  of this paper, they point out that the idea of aliasing had been illustrated graphically by Stumpf<ref name=stumpf/> ten years prior.

The 1949 Bell technical report refers to aliasing as though it is a well-known concept, but does not offer a source for the term.  [[Gwilym Jenkins]] and [[Maurice Priestley]] credit Tukey with introducing it in this context,<ref name=jenkins&priestley/> though an [[Aliasing (factorial experiments)|analogous concept of aliasing]] had been introduced a few years earlier<ref name=Finney/> in [[fractional factorial design]]s.  While Tukey did significant work in factorial experiments<ref name=Tukey-factorial/> and was certainly aware of aliasing in fractional designs,<ref name=Tukey-fraction/> it cannot be determined whether his use of "aliasing" in signal processing was consciously inspired by such designs.