Multiband Filter Circuitry, Multiband Duplexer Circuitry, and Related Radio-Frequency System

A multiband filter circuitry utilized in a radio-frequency (RF) system is disclosed. The multiband filter circuitry operates at a plurality of operating frequency bands. The multiband filter circuitry comprises at least a switchable-filtering series. Each of the at least a switchable-filtering series comprises a first terminal coupled between the antenna and the RF processing unit; a second terminal coupled to a ground; and a plurality of switchable-filtering units connected in series, each comprising a filtering unit; and a switching unit, connected to the filtering unit in parallel.