EMI-Reduction Coding Based on 8b/10b

High-speed digital signals may generate significant radiated emission and affect nearby wireless communication devices. The undesirable electromagnetic interference (EMI) of USB 3.0 to the 2.4-GHz ISM band is a well-known example. Common solutions such as shielding or layout improvement usually focus on controlling the coupling path, while few works considered the possibility of using data encoding. Based on our previous work, this paper presents a new coding method to reduce EMI at the source, with a key feature of being compatible with the conventional 8b/10b line code. In particular, the control symbols in 8b/10b are used to achieve spectrum suppression at specific target frequencies. By properly inserting preselected control symbols constantly to the output stream, a single band 7-15 dB, or dual band near 10 dB, spectrum reduction can be achieved, hence opening a window in spectrum suitable for wireless communication. The proposed coding demands a new encoder at the transmitter side, but only a slightly modified 8b/10b decoder is required at the receiver side. Various simulation and measurement validations are presented in this paper, and a real-time encoder implemented on a field programmable gate array is demonstrated.