A　frequency　synthesizer　capable　of　generating　all　the　14　sub-band　carrier　frequencies　in　3.1∼10.6GHz　band　for　multi-band　OFDM　ultra-wideband　(MB-OFDM　UWB)　transceivers　is　proposed.　It　is　composed　of　a　phase-locked　loop　(PLL),　two　single-sideband　(SSB)　mixers,　and　two　multiplexers　(MUXGHs).　Switched-cascode　architecture　with　switched　LC　tanks　is　adopted　in　the　multiplexers　to　ensure　fast　switching.　A　buffer　with　series　peaking　is　employed　for　the　output　SSB　mixer　to　enlarge　its　bandwidth.　The　synthesizer　is　designed　in　TSMC　0.18μm　CMOS　technology.　The　simulated　switching　time　between　each　sub-band　is　approximately　3ns.　The　current　consumption　excluding　that　of　the　PLL　is　25mA　under　1.8V　power　supply.　©　2010　IEEE.