Hybrid microstrip compact hairpin bandpass filter

A four-pole elliptic function band-pass filter is designed using miniaturized microstrip inter-digital hairpin resonator and step-impedance hairpin resonator. Miniaturization hairpin resonators are realized by using inter-digital structure and step-impedance structure having parallel coupled lines. The full-wave simulator IE3D is used to design the compact hairpin resonator, and to calculate the coupling coefficient of the basic coupling strictures. The response of the fabricated filters using Al₂O₃ (¿_r = 9.7) ceramic substrates are designed at a center frequency of 2 GHz. The compact size and the performance of this class of filter have been demonstrated.