Synthesis of Extracted Pole Filters Without the Extra Spikes

This paper proposes a novel synthesis procedure for unified extracted pole filters to remove extra spikes in the stopband. The ideal phase shifters in the prototype circuit can be absorbed into the resonators in the proposed circuit configuration. The synthesis approach is illustrated using a three-pole filter with one transmission zero and verified using a 11-pole filter with 2 transmission zeros. The simulated results verified the validity of the new synthesis method.