In　this　paper,　by　modeling　a　narrowband　interference　(NBI)　as　a　wide-sense　stationary　(WSS),　zero-mean　Gaussian　bandpass　random　process,　a　systematic　theoretical　framework　is　developed　for　the　first　time　to　characterize　the　operation　and　performance　improvement　of　energy　detection　(ED)　based　impulse　radio　ultra-wideband　(IR-UWB)　receivers　that　employ　a　nonlinear　Teager-Kaiser　operator　(TKO)　and　a　highpass　filter.　Furthermore,　through　both　theoretical　analysis　and　simulations,　we　have　identified　(1)　that　the　TKO　technique　can　effectively　mitigate　not　only　the　performance　degradation　caused　by　an　NBI　but　also　that　caused　by　additive　white　Gaussian　noise　and　(2)　that　a　larger　bandwidth　of　the　UWB　signal　leads　to　better　mitigation.　Therefore,　the　TKO　technique　is　considered　as　a　very　promising　technique　to　improve　the　overall　performance　of　ED-based　IR-UWB　receivers　no　matter　an　NBI　is　present　or　not.