Gang G Yu

US Patent:

20020010821, Jan 24, 2002

Filed:

Jun 11, 2001

Appl. No.:

09/878618

Inventors:

Gang Yu - Sunnyvale CA, US
Chu-Ching Nei - Los Altos CA, US

International Classification:

G06F013/00

US Classification:

710/100000

Abstract:

A USB extension system is disclosed which converts the standard USB signal into a low voltage differential signal and is installed between a USB hub or host and a USB device, and which drives the interconnecting cable with a true differential signal, i.e. a balanced signal, the problems with interference are greatly reduced. In accordance with the present invention, the standard USB signals are encoded into differential form using differential signals of different magnitudes. In one embodiment, differential signals of a “weak” magnitude are used to encode the “J” and the “K” states of the standard USB protocol, and differential signals of a “strong” magnitude are used to encode the standard “EOP” (End of Packet) USB state. In a further embodiment of the present invention, a sync signal is inserted into the data stream in order to reconcile the timing features of the standard USB protocol with the transmission delays which can be expected over long cable lengths.