Patent ID: 8019033

Claim:
A data transmission system comprising: a transmitter for transmitting a reference signal and a phase modulation signal during a data transmission period, the phase modulation signal having a phase difference with respect to the reference signal related to a value of input data, and for transmitting an adjustment signal having a predetermined phase relation with respect to the reference signal during an adjustment period before transmitting data; a receiver for outputting an output data in accordance with the phase difference between the reference signal and the phase modulation signal; variable delay means, coupled between the transmitter and the receiver, for delaying at least one of the reference signal, the phase modulation signal, and the adjustment signal transmitted from the transmitter; and control means for variably controlling a delay value of the variable delay means, so as to bring a phase relation between the reference signal received at the receiver from the transmitter and the adjustment signal received at the receiver from the transmitter into the predetermined phase relation, wherein the variable delay means comprise a first variable delay circuit provided to a first transmission line through which the reference signal is transmitted from the transmitter and a second variable delay circuit provided to a second transmission line through which the phase modulation signal is transmitted from the transmitter.