A COMPACT WIDE BANDPASS FILTER WITH GOOD SELECTIVELY

A compact Ku-band bandpass filter (BPF) with wide passband, compact size and high selectively is presented. The presented BPF is composed of two quarter-wavelength resonators and a dual-mode resonator, resulting in a compact circuit size. The transmission zeros (TZs) located at the lower and upper stopband are achieved by the mixed electromagnetic (EM) coupling and dual-mode resonator, respectively, resulting in a high frequency selectively. The measured results show minimum in-band insertion loss, fractional bandwidth and variation of group delay to be 0.9 dB, 36.2% and 0.12 ns, respectively. Also, the stopband suppression is greater than 28 dB from 5 to 10.3 GHz and 30 dB from 19.5 to 29.5 GHz. The effective circuit size of the filter is 8.43× 2.28 mm2 (0.63λg × 0.17λg , where λg is the guide wavelength of 15.1 GHz).