ThispaperpresentsanRFreceiverofzero-IntermediateFrequency(IF)architectureforCognitiveRadio(CR)communicationsystems.Zero-IFarchitecturereducetheimagerejectfilterandIFfilter,soitisexcellentinlowcost,compactvolume,andlowpowerdissipation.Thereceiveremploysthreedigitalattenuatorandahighgain,highlinearitylownoiseamplifiertoachievewidedynamicrangeof70dBandhighreceivingsensitivityof-81dBm.AfullybalancedI/QdemodulatorandadifferentialLocalOscillator(LO)chipsareusedtominimizethenegativeeffectscausedbysecond-orderdistortionandLOleakage.Inordertoselectan8MHz-channelfrom14continuousoneslocatedinUHFband(694-806MHz)accurately,approachofchannelselectivitycircuitsisproposed.TheRFreceiverhasbeendesigned,fabricated,andtest.Themeasuredresultshowsthatthenoisefigureis3.4dB,andtheerrorvectormagnitudeis7.5%whentheinputpoweris-81dBm.
