Common mode conversion noise suppression using L-Pad with asymmetric coupled lines on bended differential lines

Right-angle bended differential lines using L-Pad with asymmetric coupled lines (ACL) are proposed to suppress the differential-to-common mode conversion. The L-pad with ACL not only suppresses the mode conversion noise effectively, but also has advantages on using in practical printed circuit board (PCB) layout because it does not occupies additional PCB areas. The simulated results show that differential-to-common mode noise conversion of proposed structure is maintained under -20 dB from DC to 4.98 GHz while conventional right-angle bended differential lines provides-20 dB suppression levels only up to 1.12 GHz. Also, Time Domain Transmission (TDT) common mode noise voltage is simulated and compared with other structures. The proposed design shows significant suppression of common mode noise with 42 mV, while other structures with compensation capacitance and with only L-pad show 118 mV and 88 mV respectively. Finally, measured results are compared with simulated results and show good agreements.