A Miniaturized Dual-mode Bandpass Filter using Triangular Loop Resonator with Wide Stopband by U-Shaped Defected Ground Structure (DGS)

In this paper, miniaturized dual-mode microstrips bandpass filter using the triangular loop structure with harmonics suppression by double U-shaped deflected ground structure is proposed by contain excellent performance. The proposed filter shows a 3.6% fractional bandwidth at the center frequency of 1.4 GHz with a return loss of better than 10 dB and an insertion loss of less than 2 dB. The size of the proposed structure is 50% less than conventional dual-mode microstrip triangular loop resonator filter at the same center frequency. With proper design, the stopband performances of the propose filter have been drastically improved that the first and second spurious suppression of better than -15 dB.