A small but increasing number of boards use differential structures. How do these differ from ordinary single ended structures such as a microstrip?
Differential structures are sometimes used to interface to telecoms cables, for example “twisted pair”. The differential configuration of cables and structures is used because of its ability to maintain excellent signal quality in areas of high electrical noise without the need for excessive amplification. Explained simply, at the start of the cable the signal is transmitted into one side of the pair and at the same time it is inverted and transmitted into the other side. As the signal travels along the pair of cables (or traces) any electrical noise which appears on the cable is identical on both sides (i.e. not inverted). The receiver simply subtracts the incoming signal from the PCB or cable and the noise cancels out and the remaining signal is a high quality reproduction of the original.
