A U-shaped Complementary Open Loop Defective Ground Structure with Slow Wave Structure for Mode Conversion and Common Mode Noise Suppression

With the increase of signal rate, differential interconnection becomes more and more widely used. However, when the differential pair is asymmetric in layout, e.g., bending lines, common mode noise will be produced in the circuit, which may further cause EMI problems. In this paper, an efficient method, i.e., combing a U-shaped complementary open loop defective ground structure (DGS) with adding slow wave structure at the inner bending line, is proposed to suppress the differential-to-common mode conversion and common-mode noise of right angle bend discontinuity for differential signaling. The simulation results show that the mode conversion can be reduced to less than -50dB in the bandwidth from DC to 16GHz. Moreover, the common mode noise is also significantly suppressed.