Patent ID: 7944327

Claim:
A bandpass filter comprising: two parallel signal branches each connected, on an input side, to an input node and, on an output side, to an output node, the two signal branches forming a ring resonator, having a wave mode with a complex amplitude of {right arrow over (U)} CW =|{right arrow over (U)} CW |exp{−jφ CW } propagating in a clockwise direction with a phase φ CW and a wave mode with a complex amplitude of {right arrow over (U)} CCW =|{right arrow over (U)} CCW |exp{−jφ CCW } propagating in a counterclockwise direction with a phase φ CCW , wherein a vector sum of a resulting wave {right arrow over (U)} out at the output node of the bandpass filter at two or more stop frequencies is: {right arrow over (U)} out ={right arrow over (U)} CW +{right arrow over (U)} CCW =0, and |{right arrow over (U)} CW |=|{right arrow over (U)} CCW | and |φ CW −φ CCW |=180°, wherein the two or more stop frequencies are arranged such that a passband is formed between two stop frequencies of the two or more stop frequencies.