SIGNAL CONVERTING DEVICE AND COMMUNICATION DEVICE FOR ETC

PROBLEM TO BE SOLVED: To provide a signal converting device for performing DA conversion of a digital signal to an analog signal, and a communication device for ETC (ETC vehicle mounted device) using the signal converting device at low cost, wherein the analog signal is a sine wave having the same amplitude in a plus side and a minus side from an offset voltage. SOLUTION: The ETC vehicle mounted device 10 is constituted by a DSRC control LSI 11, a signal converter 12, an RF circuit 53, and an antenna 54. The LSI 11 produces 4-bit digital signals D0 to D3. The LSI 11 comprises a MAC circuit 61 and a RAM 21 therein. The circuit 61 produces the digital signals and applies ASK. The RAM 21 is set a conversion table for correcting distortion of the RF circuit 53, and produces the digital signals D0 to D3. The signal converter 12 is constituted by each of reference voltage generating circuits 22, 23, and a 4-bit DA converter 24. Each of the circuits 22, 23 produces reference voltages VH, VL based on control signals SH, SL. The DA converter 24 is designed to perform the DA conversion of the digital signals D0 tol D3, and to produce an analog signal Vout which is the sine wave to be varied its voltage value between each of the reference voltages VH, VL. The RF circuit 53 is designed to convert the analog signal Vout to a high frequency signal, and to transmit from the antenna 54. COPYRIGHT: (C)2006,JPO&NCIPI