a second - order bandpass filter having an improved frequency response is disclosed , in which a grounding capacitor is connected electrically to a two - port network as a feedback path so as to provide two finite transmission zeros . with the two transmission zeros , signals of second harmonic frequency and gsm signals may be blocked out from the pass band of the filter and thus filtered out . as such , the filter may be utilized in wireless local area network application . further , since no extremely small value component is used within the filter , the frequency response may not be influenced by a manufacturing process of the filter . in addition , the thus formed filter has a relatively smaller volume .