Multi-phase　passive　mixer　(PM)　first　RF　frontend　has　regained　great　concern　for　its　satisfactory　noise　performance　comparable　to　LNA-first　frontend.　Moreover,　the　re-configurable　impedance,　bi-directional　signal　transparency　and　bi-directional　impedance　translation　performance　enable　a　splendid　application　future　for　the　multi-phase　PM-first　RF　frontend.　However,　it　still　suffers　from　quite　a　few　nonidealities,　among　which　the　adjacent　Local　Oscillator　(LO)　pulse　overlap　is　the　remaining　nonideality　lacking　deep　research,　and　how　the　LO　pulse　overlap　decays　the　impedance　matching　and　noise　performance　of　multi-phase　PM-first　RF　frontend　remains　unclear.　In　this　work,　an　accurate　model　is,　for　the　first　time,　established　and　analyzed　to　reveal　how　the　LO　pulse　overlap　decays　the　impedance　matching　and　noise　performance　of　multi-phase　PM-first　RF　frontend.　The　analytical　and　simulation　results　demonstrate　that　the　impedance　matching　will　be　drastically　deteriorated　because　of　LO　overlap,　and　when　LO　pulse　overlap　exceeds　2%　the　impedance　matching　will　be　collapsed,　while　the　noise　figure　(NF)　is　deteriorated　by　3.1　dB　when　LO　overlap　ranges　from　0%　to　2%.　Moreover,　even　a　chocking　inductor　technique　and　a　technique　by　introducing　a　synchronous　phase-shifted　signal　have　been　proposed　to　suppress　the　LO　overlap,　the　gain　and　noise　performance　can　be　deteriorated　or　the　power　and　chip　area　cost　are　big.　To　address　this　question,　a　LO　pulse　overlap　suppression　technique　is　proposed　furthermore　by　introducing　an　overlap　safeguard　factor　(OLSF)　in　this　work.　The　additional　impedance　smaller　than　2　Omega　in　the　main　signal　path　makes　the　OLSF　scheme　beneficial　for　noise　and　gain　improvement,　and　the　proposed　OLSF　scheme　is　power,　area　(0.04　mm(2))　and　cost　efficient　compared　with　existing　LO　overlap　suppression　techniques.