ﻓﻮرﻳﻪ زﻣﺎنﭘﻴﻮﺳﺘﻪهﺎيﺳﻴﺴﺘﻢﺗﺒﺪﻳﻞ ٨٤ t ω jt ω j , 2 atuetx at ω jFtf ،راﺑﺪﺳﺖﺁوردﻩواﻧﺪازﻩوﻓﺎزﺁنراﺑﺪﺳﺖﺁوردﻩوﺗﺮﺳﻴﻢ ﺪﻧﻤﺎﺋﻴ . e ω jX ω jX t ω jat ω jat ω jatt ω jat )( )( dttf )( −− ±∞= ±∞= m ↔ a ١ﻣﺜﺎل ( ﻓﻮرﻳﻪ ﺳﻴﮕﻨﺎلﺗﺒﺪﻳﻞ 0,)()( >= − )( ∞< ٨٥ ٤ - ٢ - ﻓﻮرﻳﻪ ﺗﺒﺪﻳﻞ وﺟﻮد ﺷﺮاﻳﻂ ω jXj ∫ 0