A compact wideband bandpass filter with harmonic suppression using fork-shape resonators and SIS

A new and miniature wide-band bandpass filter (BPF) with 2nd harmonic-suppressed characteristic is proposed in this letter. This designed filter consists of two cascading folded fork-shape resonators paralleled with an open-ended stepped impedance stub (SIS). The harmonic-suppressed filter has been designed, fabricated, and measured. The measurement results are in good agreement with the electromagnetic (EM) simulation results. The obtained frequency responses demonstrated the filter with an excellent band-pass property, including -3 dB fractional bandwidth (FBW) 45% at the central frequency 2.2 GHz, less than 1.4 dB insertion loss within the passband, and broad stopband rejection.