1. A filtering device, comprising:
a housing, comprising an inner cavity accessible by an opening in the housing;
a resonant conductor, removably disposed inside the inner cavity by inserting the resonant conductor vertically or horizontally into the inner cavity via the opening;
a pressing element having one end disposed on the housing and another end suspended, and facing a position of an open-circuit end of the resonant conductor, wherein the pressing element is configured such that a distance between the pressing element and the resonant conductor is changeable when the pressing element pressed or drawn to adjust a resonant frequency; and
a cavity terminal integrated with the housing, configured to electrically connect a short circuit end of the resonant conductor to the housing, and configured to support the resonant conductor when disposed inside the inner cavity.

2. The filtering device according to claim 1, wherein the housing comprises at least one inner cavity, and at least one resonant conductor is disposed inside the inner cavity.

3. The filtering device according to claim 1, wherein the resonant conductor is a metal strip, a microstrip, a strip line, or a printed circuit board (PCB).

4. The filtering device according to claim 1, wherein
the pressing element is of a metal sheet-shaped structure or a metal peg-shaped structure.

5. The filtering device according to claim 1, further comprising:
a fastening terminal, disposed on an outer side of the housing, and configured to fasten the filtering device; and
a wiring port, disposed on an outer side of the housing, and configured to connect to a wire.

6. The filtering device according to claim 1, wherein:
the pressing element is an integrated structure of the housing; and
inserting the resonant conductor vertically or horizontally into the inner cavity via the opening automatically aligns the pressing element with a corresponding feature of the resonant conductor, such that changing the distance between the pressing element and the resonant conductor adjusts the resonant frequency.

7. The filtering device according to claim 1, wherein the housing comprises one or more inner cavities and a plurality of resonant conductors, and wherein
at least two of the resonant conductors are disposed inside a same one of the one or more inner cavities and are electrically connected to each other.

8. The filtering device according to claim 1, wherein:
the housing comprises a plurality of inner cavities and a plurality of resonant conductors; and
the resonant conductors are in the plurality of inner cavities and are electrically connected to each other.

9. The filtering device according to claim 8, wherein each resonant conductor of the plurality of resonant conductors is removably disposed inside a respective one of the inner cavities by inserting the resonant conductor vertically or horizontally into the respective one of the inner cavities via the opening.