Abstract: Electromagnetic field transmissions between a sensor unit mounted on the inside surface of a tire and a sensor control unit mounted on the vehicle body are attenuated by the wall surface of a tire disposed between the units, and sensitivity is reduced. A booster antenna (18) is embedded in the tire wall surface between the sensor unit (6) and the sensor control unit (10). The booster antenna (18) is a coil antenna, and is configured so that the resonance frequency, which corresponds to the impedance and capacitance component of the booster antenna coil, corresponds to the frequency f0 of the transmission electromagnetic field of the sensor control unit (10). The booster antenna (18) is disposed in a position in which a magnetic coupling is formed with the coil antenna of the sensor unit (6), and transmissions via the electromagnetic field between the sensor unit (6) and the sensor control unit (10) are carried out through the booster antenna (18).

Abstract: The position of the rotation of a tire complicates the establishing of a wireless connection between a sensor unit attached to the tire and a sensor control unit attached to a vehicle body. A reflection plate is attached to an inner surface of a wheel housing at a position different from that of a sensor control unit. A transmission electromagnetic field from the sensor control unit is reflected by the metal reflection plate and transmitted to a sensor unit rotated to a position to which the field does not readily reach directly from the sensor control unit. The sensor unit varies an impedance of a coil antenna in accordance with transmission data, and generates a variation in the transmission electromagnetic field. The variation is detected via the reflection plate as a variation in a transmission load of the sensor control unit, and the transmission data from the sensor unit is detected in the sensor control unit.

Abstract: Electromagnetic field transmissions between a sensor unit mounted on the inside surface of a tire and a sensor control unit mounted on the vehicle body are attenuated by the wall surface of a tire disposed between the units, and sensitivity is reduced. A booster antenna (18) is embedded in the tire wall surface between the sensor unit (6) and the sensor control unit (10). The booster antenna (18) is a coil antenna, and is configured so that the resonance frequency, which corresponds to the impedance and capacitance component of the booster antenna coil, corresponds to the frequency f0 of the transmission electromagnetic field of the sensor control unit (10). The booster antenna (18) is disposed in a position in which a magnetic coupling is formed with the coil antenna of the sensor unit (6), and transmissions via the electromagnetic field between the sensor unit (6) and the sensor control unit (10) are carried out through the booster antenna (18).

Abstract: The position of the rotation of a tire complicates the establishing of a wireless connection between a sensor unit attached to the tire and a sensor control unit attached to a vehicle body. A reflection plate (20) is attached to an inner surface of a wheel housing (16) at a position different from that of a sensor control unit (10). A transmission electromagnetic field from the sensor control unit (10) is reflected by the metal reflection plate (20) and transmitted to a sensor unit (6) rotated to a position to which the field does not readily reach directly from the sensor control unit (10). The sensor unit (6) varies an impedance of a coil antenna in accordance with transmission data, and generates a variation in the transmission electromagnetic field. The variation is detected via the reflection plate (20) as a variation in a transmission load of the sensor control unit (10), and the transmission data from the sensor unit (6) is detected in the sensor control unit (10).

Abstract: A tire inflation pressure determining system is provided in which measurement results are transmitted to the exterior without providing a high precision oscillation circuit to a tire-mounted air pressure determining system. An LC resonance circuit is composed of a coil Ls and an inflation pressure sensor in which the electric capacitance varies in accordance with tire air pressure. The fluctuations of the electromagnetic field having a frequency f0 generated by a sensor control unit are sensed in a coil L2, a clock is generated based on the sensed fluctuations, the clock is inputted to a coil Le that is transformer coupled to the coil Ls, and the LC resonance circuit is excited.

Abstract: A tire inflation pressure determining system is provided in which measurement results are transmitted to the exterior without providing a high precision oscillation circuit to a tire-mounted air pressure determining system. An LC resonance circuit is composed of a coil Ls and an inflation pressure sensor in which the electric capacitance varies in accordance with tire air pressure. The fluctuations of the electromagnetic field having a frequency f0 generated by a sensor control unit are sensed in a coil L2, a clock is generated based on the sensed fluctuations, the clock is inputted to a coil Le that is transformer coupled to the coil Ls, and the LC resonance circuit is excited.