Abstract: A wireless communication device and a filter are provided. The filter has an input end and an output end and includes a first energy storage element, a first series resonant circuit, a second series resonant circuit, a first parallel resonant circuit and a second parallel resonant circuit. The first and the second series resonant circuits respectively have a first capacitor and a first inductor connected in series. The first and the second parallel resonant circuits respectively have a second capacitor and a second inductor connected in parallel. The first series resonant circuit and the first parallel resonant circuit are electrically connected in cascade between a first end of the first energy storage element and a ground, and the second series resonant circuit and the second parallel resonant circuit are electrically connected in cascade between a second end of the first energy storage element and the ground.

Abstract: A wireless communication device and a filter are provided. The filter has an input end and an output end and includes a first energy storage element, a first series resonant circuit, a second series resonant circuit, a first parallel resonant circuit and a second parallel resonant circuit. The first and the second series resonant circuits respectively have a first capacitor and a first inductor connected in series. The first and the second parallel resonant circuits respectively have a second capacitor and a second inductor connected in parallel. The first series resonant circuit and the first parallel resonant circuit are electrically connected in cascade between a first end of the first energy storage element and a ground, and the second series resonant circuit and the second parallel resonant circuit are electrically connected in cascade between a second end of the first energy storage element and the ground.

Abstract: A miniature microstrip antenna having a circuit board with a suitable length and a suitable width, and especially a microstrip antenna of which the size is reduced but the antenna still keeps the broadband function in all the directions, wherein, the circuit board does not have any metallic portion in the back side thereof. A ¼&lgr; microstrip line is rolled on the surface of the circuit board in the shape of a rectangular spiral, the end of the rectangular spiral microstrip line is connected via a vertical section to another {fraction (1/20)}&lgr; microstrip line which acts as an open-stub. A junction of the rectangular spiral microstrip line with the open-stub acts as a signal feeder point; a ground plane is provided near the signal feeder point but does not connect with the signal feeder point, the ground plane is punched to form a hole to get a desired harmonic oscillation frequency shifting. The miniature microstrip antenna has the size thereof reduced can thus be obtained.