Tunable filter

A tunable filter, comprising a first waveguide body, a second waveguide body, a metal plate, a tuning piece, and a driving piece, wherein

• a first cavity is disposed in the first waveguide body, a second cavity is disposed in the second waveguide body, the first waveguide body is in butt joint with the second waveguide body, an input end and an output end are formed on both ends of a juncture of the first waveguide body and the second waveguide body, and an electromagnetic wave in the tunable filter is propagated from the input end to the output end;
• the metal plate is sandwiched between the first waveguide body and the second waveguide body, multiple windows are disposed on the metal plate, the multiple windows are distributed along a propagation direction of the electromagnetic wave of the tunable filter, and the first cavity and the second cavity are in communication and are symmetrically distributed on both sides of the metal plate;
• the tuning piece comprises a dielectric pull-rod and multiple metal sheets connected to the dielectric pull-rod, the dielectric pull-rod traverses the first waveguide body, the dielectric pull-rod protrudes out of the first waveguide body and is connected to the driving piece, the multiple metal sheets are disposed inside the first cavity, and the multiple metal sheets and the multiple windows are distributed in a same manner and are disposed in a one-to-one correspondence;
• and
• the driving piece drives the tuning piece to move relative to the metal plate, to adjust a frequency of the tunable filter.