Abstract: In a wireless communication system, an approach determination section determines whether a portable device is inside of a nearby area of one of a plurality of transmitting antennas transmitting a primary signal. When the approach determination section determines that the portable device is inside of the nearby area, a transmission control section changes a driving voltage of another one of the transmitting antennas disposed outside of the nearby area, such that a communication area of the another one of the transmitting antennas is increased to encompass the nearby area of the one of the transmitting antennas, and the primary signal is retransmitted from the another one of the transmitting antennas.

Abstract: In a wireless communication system, an approach determination section determines whether a portable device is inside of a nearby area of one of a plurality of transmitting antennas transmitting a primary signal. When the approach determination section determines that the portable device is inside of the nearby area, a transmission control section changes a driving voltage of another one of the transmitting antennas disposed outside of the nearby area, such that a communication area of the another one of the transmitting antennas is increased to encompass the nearby area of the one of the transmitting antennas, and the primary signal is retransmitted from the another one of the transmitting antennas.

Abstract: The size of an antenna coil is reduced, and it is possible to prevent a lowering of the reception sensitivity due to a difference of the arrangement position of the antenna coil. On a winding frame of a ferrite core, a first coil and a second coil are wound in such a manner that their winding axes orthogonally intersect each other. A third coil is wound around an outer circumference of the first coil and the second coil in such a manner that the third coil's winding axis orthogonally intersects the winding axes of the first coil and the second coil.

Abstract: The size of an antenna coil is reduced, and it is possible to prevent a lowering of the reception sensitivity due to a difference of the arrangement position of the antenna coil. On a winding frame of a ferrite core, a first coil and a second coil are wound in such a manner that their winding axes orthogonally intersect each other. A third coil is wound around an outer circumference of the first coil and the second coil in such a manner that the third coil's winding axis orthogonally intersects the winding axes of the first coil and the second coil.

Abstract: The size of an antenna coil is reduced and it is possible to prevent lowering of the reception sensitivity due to difference of the arrangement position of the antenna coil. On a winding frame (3) of a ferrite core (2), a first coil (5) and a second coil (6) are wound in such a manner that their winding axes orthogonally intersect each other, and a third coil (12) is wound around an outer circumference of the first coil (5) and the second coil (6), so that a winding axis is provided to be orthogonal to the winding axes of the first coil (5) and the second coil (6).

Abstract: An electronic key system has a portable electronic key and a transmitter provided in a vehicle. The key and the transmitter have respective LC resonance circuits including antenna coils that can be electromagnetically coupled. The portable device has a charge capacitor and a diode. The capacitor is charged with a voltage induced by the coil when the LC resonance circuit resonates. The electronic key is enabled to communicate with the transmitter with the charged voltage of the charge capacitor when a built-in battery runs down.

Abstract: A reception antenna is formed of a column-profiled ferrite core and three antenna coils, each of which is formed by winding electric wire around the core. Each central axis of the three antenna coils is mutually disposed orthogonally at a barycenter of the core. Each of the three antenna coils is symmetrical with respect to the barycenter. A third antenna coil and each of a first antenna coil and a second antenna coil are overlapped with a space. The first antenna coil and the second antenna coil are overlapped with direct contact, where a starting end of the second antenna and a terminating end (outward end) of the first antenna is connected.

Abstract: An electronic key system has a portable electronic key and a transmitter provided in a vehicle. The key and the transmitter have respective LC resonance circuits including antenna coils that can be electromagnetically coupled. The portable device has a charge capacitor and a diode. The capacitor is charged with a voltage induced by the coil when the LC resonance circuit resonates. The electronic key is enabled to communicate with the transmitter with the charged voltage of the charge capacitor when a built-in battery runs down.

Abstract: A reception antenna is formed of a column-profiled ferrite core and three antenna coils, each of which is formed by winding electric wire around the core. Each central axis of the three antenna coils is mutually disposed orthogonally at a barycenter of the core. Each of the three antenna coils is symmetrical with respect to the barycenter. A third antenna coil and each of a first antenna coil and a second antenna coil are overlapped with a space. The first antenna coil and the second antenna coil are overlapped with direct contact, where a starting end of the second antenna and a terminating end (outward end) of the first antenna is connected.

Abstract: A synchronization circuit modulates a data signal with an amplitude shift keying (ASK) modulation method using an ASK modulation signal to output a modulated signal under the condition that the ASK modulation system and data signal are synchronized with each other. A drive circuit executes a push-pull operation based on the modulated signal and a resonance circuit resonates, under the push-pull operation of the drive circuit, to transmit a transmission signal in a radio wave. The synchronous signal controls a switching device to cut off a connection between the resonance circuit and the ground in synchronization with the modulated signal. Thereby, the transmission signal is generated sharply in the signal transmitter.

Abstract: A height sensor has an exciting coil for generating an alternating magnetic field and a pickup coil for detecting the magnetic field. The exciting coil is fixed to a suspension arm and the pickup coil is fixed to a body so as to face each other. Distance between these coils is determined by a voltage outputted from the pickup coil, and a height of the vehicle is calculated from the distance between these coils by taking the mounting position of the pickup coil on the suspension arm into account. The height sensor is readily fixed and a detection accuracy is improved by setting the mounting position of the pickup coil in a range of {fraction (1/10)} to ½ of a length of the suspension arm from a connecting portion between the suspension arm and the body.

Abstract: Markers each comprising an electromagnetic coil are installed on the surface of a road at a lateral center line of a running lane of the road at predetermined intervals. Provided for each of the markers, a driving signal generating circuit drives the associated marker so that the marker transmits an alternating current magnetic field. Alternating current magnetic field receiving devices each comprising an electromagnetic coil are installed on the front bumper of a vehicle at positions symmetrical with respect to the lateral center line of the vehicle. While the vehicle is running, the alternating current magnetic field receiving devices sequentially receive the alternating current magnetic fields generated by the markers one field after another. A microcomputer receives detection voltages generated by the alternating current magnetic field receiving devices through detection circuits and determines the lateral position of the vehicle from the detection voltages.

Abstract: A controller drives a key interlock solenoid to lock a key so that the key cannot be pulled out of a key cylinder when a shift lever is not at a parking position or while an identification code is being sent to a transponder mounted in the key. Thus, the key cannot be pulled out of the key cylinder during the writing of the identification code in the transponder.

Abstract: The power feeding efficiency and the communicable range of an automatic answering system are improved in an automatic answering system using a transponder which performs code communication using amplitude modulation of a carrier with an electromagnetic coupling transponder mounted in a key or the like. In a transceiver for performing the code communication with the transponder via an antenna coil, a circuit for driving the antenna coil in a transceiver based on clock is implemented by a bridge-type complementary circuit of transistors. Thereby, driving current is increased. Meanwhile, a circuit for controlling the driving mode based on a write signal is implemented by a parallel circuit of a transistor to which a power-supply voltage is applied and a resistor. Thereby, a current corresponding to a resistance of the resistor flows through the antenna coil even during the minimum driving when the transistor is turned off, thus improving the power feeding efficiency and the communicable range of the system.