Design of a compact narrow band-pass filter with λg/4 short stubs

In this paper, a narrow band pass Alter with reduced size using the λ_g/4 short stubs is presented. The filter size is reduced by realization of transmission line at the second harmonic while the power can be transferred to the output using the fundamental frequency band generated in the resonator and the transmission line in which the impedance mismatching technique is adopted. The experimental results show that the insertion loss is 2.0 dB and return loss is 11.1 dB, and the fractional bandwidth is 10% at the center frequency of 5.8 GHz. The Alter size is 19.7??8.6 mm².