A Simple Technique for Multiple Configurable Transmission Zeros in λ/2 Resonator Filters

A 2
^nd
order bandpass filter using tapped-fed λ/2 hairpin resonators with unequal-length arms is presented. The proposed filter geometry introduces a transmission zero (TZ) in the upper and lower stopbands simultaneously. The frequencies of the TZs can be controlled by changing the lengths of the resonator arms. A single stub matching network is proposed to improve impedance matching after the TZs are re-configured. The proposed matching network introduces an additional configurable TZ in the upper stopband. The design offers several degrees of freedom to alter the passband and stopband performance. The overall dimensions of filter are 0.18λ × 0.3λ.