Communication circuit and vehicle communication apparatus using the same

A vehicle communication apparatus comprising:

• a communication circuit including a transmission unit and a reception unit, the transmission unit being configured to transmit an information bit string for controlling an in-vehicle device to the reception unit,
• wherein the transmission unit includes:
• a bit string generation circuit that sequentially outputs a start bit and then outputs the information bit string;
• a first modulation circuit that modulates a first carrier wave by the start bit output from the bit string generation circuit to generate a first high frequency signal;
• a second modulation circuit that modulates a second carrier wave by the information bit string output from the bit string generation circuit to generate a second high frequency signal, wherein the first carrier wave has a frequency different from that of the second carrier wave;
• and
• a transmission circuit that transmits the first high frequency signal and the second high frequency signal from a transmitting antenna, and
• wherein the reception unit includes:
• a reception circuit that receives a signal transmitted from the transmission unit by a receiving antenna;
• a first detector circuit that is connected to the reception circuit and detects a signal of the first carrier wave to demodulate the start bit;
• a second detector circuit that is connected to the reception circuit and detects a signal of the second carrier wave to demodulate the information bit string;
• and
• a detection circuit that is synchronized by the start bit and reads out the information bit string demodulated by the second detector circuit.

A vehicle communication apparatus comprising:

• a communication circuit including a transmission unit and a reception unit, the transmission unit being configured to transmit an information bit string for controlling an in-vehicle device to the reception unit,
• wherein the transmission unit includes:
• a bit string generation circuit that sequentially outputs a start bit and then outputs the information bit string;
• a first modulation circuit that modulates a first carrier wave by the start bit output from the bit string generation circuit to generate a first high frequency signal;
• a second modulation circuit that modulates a second carrier wave by the information bit string output from the bit string generation circuit to generate a second high frequency signal, wherein the first carrier wave has a frequency different from that of the second carrier wave;
• and
• a transmission circuit that transmits the first high frequency signal and the second high frequency signal from a transmitting antenna, and
• wherein the reception unit includes:
• a reception circuit that receives a signal transmitted from the transmission unit by a receiving antenna;
• a first detector circuit that is connected to the reception circuit and detects a signal of the first carrier wave to demodulate the start bit;
• a second detector circuit that is connected to the reception circuit and detects a signal of the second carrier wave to demodulate the information bit string;
• and
• a detection circuit that is synchronized by the start bit and reads out the information bit string demodulated by the second detector circuit,
• wherein the transmitting antenna is provided adjacent to an operation switch provided around a vehicle seat or provided to a remote controller for the in-vehicle device, and
• wherein the transmitting antenna transmits a signal to a body of a user who operates the operation switch, and the receiving antenna include a conductor provided in a seat face of the vehicle seat and receives the signal transmitted from the transmitting antenna through the body of the user.