Miniaturized bandpass filter with high frequency selectivity and wide upper stpoband

A miniaturized bandpass filter (BPF) with high frequency selectivity and wide upper stopband is presented. The presented bandpass filter is constructed by using the capacitance loaded square meander loop resonator. Due to capacitive load, the resonator can exhibit slow-wave characteristics, which can be utilized to reduce size and suppress harmonics. The two degenerate-mode resonances are used to form the passband while two transmission zeroes are generated on each side of the passband so as to obtain high frequency selectivity. The circuit area of bandpass filter is only 0.14λg×0.14λg, where λg is the guided wavelength at the center frequency. The measured results reach good agreement with simulated results.