Patent ID: 7825746

Claim:
An integrated balanced-filter, comprising: a first electrical circuit, including: an unbalanced terminal for transceiving an unbalanced signal, a first resonator having a first node connected to a ground and a second node, and a fourth resonator having a first node connected to the ground and a second node, the second node of the fourth resonator is connected to the unbalanced terminal through a first coupling element and connected to the second node of the first resonator through a fourth coupling element; and a second electrical circuit, including: first and second balanced terminals for transceiving a balanced signal, a second resonator having a first node connected to the ground and a second node connected to the first balanced terminal through a second coupling element, and a third resonator having a first node connected to the ground and a second node connected to the second balanced terminal through a third coupling element, and the second resonator being positively coupled with the first resonator, and the third resonator being negatively coupled with the first resonator, and each of the resonators includes a respective capacitive element and a respective inductive element connected in parallel to the corresponding capacitive element, wherein the second coupling element includes a first notch filter at the first balanced terminal and being serially connected between the second resonator and the first balanced terminal; and the third coupling element includes a second notch filter at the second balanced terminal and being serially connected between the third resonator and the second balanced terminal, the first coupling element, the first resonator, the fourth coupling element, the fourth resonator, the second resonator, and the second coupling element form a first third-order bandpass filter; and the first coupling element, the first resonator, the fourth coupling element, the fourth resonator, the third resonator, and the third coupling element form a second third-order bandpass filter.