Compact Wide Stopband Bandpass Filter on Multilayer Organic Substrate

We present the design and development of a compact wide stopband bandpass filter using novel quasi-lumped LC resonators on a defected ground structure. The resonators are built on a multilayer organic substrate and are coupled to external circuits by shunt-inductive impedance inverters. Experimental results show that the filter has a center frequency of 960 MHz and a 3 dB fractional bandwidth of 8%. The filter has a wide stopband that has an out-of-band rejection of better than 30 dB up to five times of the center frequency. The size of the filter is 5.4 mm × 27 mm or 0.027λ_g×0.132λ_g, where λ_g is guided wavelength at 960 MHz.