In　this　paper,　a　3rd　order　active-RC　Low-Pass　Filter　(LPF)　is　proposed　for　a　zero-IF　receiver.　The　LPF　enables　85/215/430　KHz　passband　selection　and　3　dB　per　step　gain　adjustment　from　0　to　45　dB.　In　order　to　deal　with　the　deviation　of　the　filter　cut-off　frequency　caused　by　process　variation,　an　automatic　frequency　tuning　circuit　is　applied　to　the　filter,　which　can　cover　the　RC　value　variation　of　±40%.　The　low-pass　filter　circuit　is　implemented　in　55　nm　CMOS　process.　The　measurement　results　show　that　when　the　cut-off　frequency　is　85/215/430　KHz,　the　rejection　at　485/615/830　KHz　is　48/32/24　dB　respectively.　The　passband　ripple　is　1.2/0.3/2.5　dB　respectively.　The　filter　consumes　2.5　mA　from　2　V　supply.　The　area　of　the　filter　circuit　is　350　um　×　750　um.　©　2023　IEEE.