Patent ID: 7212085

Claim:
A filter assembly comprising: a bandpass filter coupled to an input terminal, a first output terminal and a second output terminal; a first resonator coupled in series with the first output terminal; a second resonator coupled in series with the second output terminal; a third resonator coupled in parallel with the bandpass filter and the second resonator; and a fourth resonator coupled in parallel with the bandpass filter and the first resonator; wherein an unbalanced signal received at the input terminal is transformed to a balanced signal by the bandpass filter and fed to the first and fourth resonators and the second and third resonators via the first and second output terminals respectively; wherein the bandpass filter generates a first pass band having a first center frequency and at least two noise pass bands having different center frequencies and the combination of the first to fourth resonators generates a second pass band having a second center frequency and at least two noise rejection bands having different center frequencies; and wherein an electrode area ratio of the first resonator to the third resonator is adjusted so that the central frequencies of the two noise rejection bands are respectively the same as the central frequencies of the two noise pass bands.