A novel miniaturized dual-mode zeroth-order ring bandpass filter with only one left-handed unit

In this paper, a novel miniaturized dual-mode ring bandpass filter is realized and studied. By using only one resonant-type left-handed unit with complementary split ring resonator to combine with a microstrip line, the ring configuration can provide two orthogonal zeroth-order resonance modes, and its occupied area can be reduced by about 82% compared with the conventional one. The filter has the first spurious response 2.58 times away from the central frequency, so its spurious suppression characteristics is also improved. The filter performance is demonstrated by our measured S-parameters, with good agreement obtained as compared with the simulated ones.