Multi-band filter

A multi-band filter configured to provide a plurality of frequency bands, comprising:

• a circuit board;
• a first resonator having a first portion and an opposite second portion;
• a second resonator having a first portion and an opposite second portion;
• and
• a coupling element configured to couple the first resonator with the second resonator, wherein the coupling element comprises:
• a first coupling capacitor disposed between the first portion of the first resonator and the first portion of the second resonator, wherein a terminal of the first coupling capacitor is electrically connected to the first resonator, and another terminal of the first coupling capacitor is electrically connected to the second resonator;
• a second coupling capacitor disposed between the second portion of the first resonator and the second portion of the second resonator, wherein a terminal of the second coupling capacitor is electrically connected to the first resonator, and another terminal of the second coupling capacitor is electrically connected to the second resonator;
• a first short-circuited stub electrically connected to the first coupling capacitor and a ground plane;
• and
• a second short-circuited stub electrically connected to the second coupling capacitor and the ground plane;
• wherein the first resonator, the second resonator and the coupling element are disposed on the circuit board, and the first coupling capacitor and the second coupling capacitor are interdigital capacitors.