Adjustable filter and adjustable duplexer

The utility model discloses an adjustable filter, which comprises a cavity and a tuning mechanism, at least three waveguide resonant cavities are arranged in the cavity. Wherein direct coupling between adjacent waveguide resonant cavities is realized through a direct coupling window, cross coupling between non-adjacent waveguide resonant cavities is realized through a cross coupling structure, atleast one slit is formed in the cavity wall of the same side of each waveguide resonant cavity, and the electrical length of each slit is smaller than the half wavelength of the highest working frequency of the adjustable filter; the tuning mechanism comprises a group of dielectric sheets in one-to-one correspondence with the slits and a driving mechanism, and all the dielectric sheets can be driven by the driving mechanism to be inserted into the corresponding waveguide resonant cavities at the same depth through the corresponding slits without friction at the same time. The utility model also discloses an adjustable