Patent ID: 8749321

Claim:
A Radio Frequency (RF) filter comprising: a coupler configured to receive an input signal through a first port of the coupler, to divide the input signal, to output divided signals through second and third ports of the coupler, to combine signals received through the second and third ports of the coupler according to phases of the signals, and to output the combined signal through the first port of the coupler or as an output signal of the RF filter through a fourth port of the coupler; a first filter unit having a first port of the first filter unit connected to the second port of the coupler and a second port of the first filter unit connected to the third port of the coupler, for having a predetermined frequency filtering characteristic; and a second filter unit connected to the fourth port of the coupler for outputting the output signal of the RF filter; wherein the first filter unit consists of one filter element, the first port of the first filter unit is an input port of the filter element and the second port of the first filter unit is an output port of the filter element, and the first and second filter units have different predetermined numbers of stages.