Microwave　photonic　systems　process　the　electrical　signal　in　optical　domain　so　that　the　characteristics　of　the　output　optical　signals　include　the　transfer　function　of　the　signal　processing　link.　In　this　paper,　we　review　our　recent　works　about　a　microwave　photonic　repeater,　self-interference　cancellation,　and　microwave　signal　coupling　techniques.　First,　based　on　a　photonic　repeater　consisting　of　a　dual-polarized　dual-parallel　Mach-Zehnder　modulator　(DP-DPMZM)　and　a　polarization　controller　(PC),　four　different　down-conversion　states　can　be　performed.　Two　separate　local　oscillator　signals　(LO)　also　enable　frequency　down-conversion　of　microwave　signals　in　different　frequency　bands.　Secondly,　a　dual-parallel　dual-drive　Mach-Zehnder　modulator　(DP-DDMZM)　and　a　low-frequency　LO　signal　source　are　used　to　achieve　self-interference　cancellation　and　harmonic　down-conversion　(SIC+HDC)　for　an　in-band　full-duplex　(IBFD)　system.　Finally,　for　the　microwave　photonic　coupling　technique,　a　photonic　microwave　hybrid　splitter　(PMHS)　and　a　photonic　microwave　hybrid　combiner　(PMHC)　are　proposed,　respectively.　The　PMHS　and　PMHC　individually　controls　the　amplitude　and　phase　of　the　two　signals　by　adjusting　the　direct　current　(DC)　biases　of　modulators.　Our　proposed　signal　processing　techniques　are　very　promising　for　flexible　microwave　signal　processing,　radars,　and　wireless　communications.