3、ter is put forward based on the idea of"virtual instruments".Itmainlyaimstorealizefrequencycharacteristictestsystemusingvirtualinstrumentdevelopment——LabVIEWprovidedbytheNICompanyintheUnitedStatesandcombingthecorrespondinghardwarecondition.Thesystemincludedthethreemodulessuchassignalproduced,d