PLANAR BANDPASS FILTER WITH 100-DB SUPPRESSION UP TO TENFOLD PASSBAND FREQUENCY

This paper proposes a miniature microwave bandpass fllter. It comprises quasi-lumped suspended substrate stripline resonators of a new type. Their common substrate consists of two contiguous dielectric layers. Every resonator in the fllter has three parallel strip conductors. Two of them are placed on the outer substrate surfaces and the rest is placed inside the substrate. The fllter of the sixth order was designed with the use of special optimization rules that are universal for all resonator fllters. The substrate of the fabricated fllter was made of RT/Duroid 5880 ("r = 2:2, tan- = 0:002) with thickness of 0.127mm. It has dimensions of 12mm £ 45:5mm. The measured passband has a center frequency of 1.01GHz, 3-dB fractional bandwidth of 11%, and minimum insertion loss of 1.4dB. The 100-dB upper stopband extends up to 10.5GHz.