Abstract: A receiver for spread spectrum communication includes a receiver for receiving a wireless signal, a demodulator for demodulating the wireless signal into a spread spectrum signal, a correlation value calculator for calculating a correlation value between the spread spectrum signal and a spreading code having a predetermined number of chips, a synchronization detector for detecting a synchronization point between the spread spectrum signal and the spread signal based on the correlation value, a despreading device for despreading the spread spectrum signal based on the synchronization point, a noise level detector for detecting a noise level of the wireless signal, and a code number setting device for determining the number of chips of the spreading code in such a manner that there is a positive correlation between the noise level and the number of code portions.

Abstract: A helical antenna includes a ground plate, a first helical portion spirally wound perpendicular to the plate, a second helical portion spirally wound perpendicular to the plate and surrounding the first helical portion radially outward of the first helical portion, and a feeder circuit. The circuit includes an oscillator, a divider connected to the oscillator, a first phase shifter connected between a first output terminal of the divider and a feeding point of the first helical portion, and a second phase shifter connected between a second output terminal of the divider and a feeding point of the second helical portion. Length of one turn of the first helical portion is equal to a result of multiplication of a wavelength of oscillation of the oscillator by N. Length of one turn of the second helical portion is equal to a result of multiplication of the wavelength by M (M>N).

Abstract: A batteryless tire inflation pressure detecting apparatus includes, on the body of a vehicle, antennas and a transmitter transmitting radio waves through the antennas. The apparatus also includes, on each wheel of the vehicle, a pressure sensor sensing the pressure of a tire, a transceiver, and a charging unit powering the pressure sensor and the transceiver. The charging unit is charged with electric power induced by a corresponding one of the radio waves received by the transceiver. The apparatus further includes, on the body of the vehicle, a receiver receiving pressure signals transmitted by the transceivers, a pressure determiner determining the pressures of the tires based on the pressure signals, and a controller. To minimize influence of the radio waves on neighboring devices, the controller controls the transmitter so that least two of the radio waves are transmitted at different times, or at the same with a phase difference therebetween.

Abstract: A tire inflation pressure detecting apparatus includes a second transceiver provided on the body of a vehicle which changes its operation alternately between a second transmitter and a second receiver mode, thereby intermittently transmitting a radio wave. A first transceiver provided on a wheel of the vehicle operates in a first receiver mode to receive the radio wave, thereby charging a charging unit. When the charging unit has been sufficiently charged, the first transceiver changes operation thereof from the first receiver mode to a first transmitter mode, in which the first transceiver first repeatedly transmits an informing signal at predetermined time intervals for a predetermined time period and then transmits a pressure signal. When the informing signal is received by the second transceiver in the second receiver mode, the second transceiver keeps its operation in the second receiver mode until the pressure signal is completely received.

Abstract: A radio signal detector includes first and second detector circuits. The first detector circuit has a higher detection sensitivity to detect a radio signal earlier than the second detector circuit. The second detector circuit has a lower detection sensitivity to detect the radio signal accurately. When the second detector circuit detects the radio signal, it starts up a microcomputer. When the first detector circuit detects the radio signal, a time counter starts to count time. After being started up, the microcomputer acquires a time difference between the radio signal detection by the first detector circuit and the start-up. The microcomputer determines time of radio signal transmission by a radio signal transmitter device based on the determined time difference, and outputs control information after an elapse of a predetermined time.

Abstract: In a wireless communication system, a portable device and an in-vehicle device wirelessly communicate with each other by a spread spectrum method. The in-vehicle device transmits a synchronization signal indicative of a reference period to the portable device. The in-vehicle device performs code acquisition for only a portion of a spread wireless signal received from the portable device. The portion has a starting point in a search period from a search start point to a search end point. The search start point is identified based on the reference period and a predetermined first correction time. The search end point is identified based on the reference period and a predetermined second correction time.

Abstract: An antenna apparatus includes a substrate having a GND pattern land and an electric power feed pattern land on a same surface, an outer element extending away from the land in a spiral shape, and an inner element extending along an axis of the outer element in a spiral shape with a space interposed between itself and the outer element. The outer element and the inner element of the antenna apparatus respectively serve as one of a signal line and a GND line, and are supported by a retainer member to have predetermined relationship on a land formation surface. The retainer member is made of dielectric body, and the two elements respectively have a surface mount portion at one end that is to be fixed onto the substrate with electrical connection to corresponding lands. The surface mount portions are formed substantially parallel to the land formation surface.

Abstract: An antenna apparatus includes an antenna and a support member. The antenna has (i) an outer element, which has a spiral section prolonged spirally in an axial direction, and (ii) an inner element, which has a spiral section prolonged spirally in the axial direction and is surrounded with an interval space by the outer element. The antenna is a terminal open type in which one of the two elements is used as a signal line and the other is used as a GND line. The support member includes a dielectric member and contacts each of the spiral sections of the outer and inner elements while supporting the outer and inner elements in a predetermined positional relationship. Further, the number of turns of the spiral section in the inner element is equal to or less than the number of turns of the spiral section in the outer element.

Abstract: An antenna apparatus includes an antenna and support member. The antenna has a double spiral structure to include (i) an outer element, which has a spiral section prolonged spirally in an axial direction, and (ii) an inner element, which has a spiral section prolonged spirally in the axial direction and is surrounded with an interval space by the outer element. The support member is made of dielectrics and holds the two elements in a predetermined positional relationship by contacting the spiral sections of the two elements. The support member contacts the spiral sections wholly along the prolonged direction. One of the two elements is connected with a high frequency wave source at one end portion along the axial direction while the other is connected with the high frequency wave source at the other end portion along the axial direction. The antenna functions as a terminal short circuit type.

Abstract: A first trigger unit and a second trigger unit output trigger signals to transceivers disposed for the four wheels of a vehicle. The first and second trigger units are attached to wall surfaces of tire housings corresponding to the left front and left rear wheels respectively. Each of the first and second trigger units is arranged in a position of the wall surface having an angle from 5 to 25 degrees with respect to the side of the corresponding wheel. Transceivers attached to a right front and right rear wheels are thus located farther from the trigger units than the left front and left rear wheels, respectively. Such arrangement allows the transceivers attached to the right front and right rear wheels to receive the outputted trigger signals with sufficient accuracy due to high field strength.

Abstract: A receiving device for spread spectrum communication includes a phase determining unit and a data demodulating unit. The receiving device receives a signal spread and modulated with first spreading code. The phase determining unit calculates a cross correlation between the received signal and a second spreading code and determines a phase P(0) of the received signal based on the cross correlation. The data demodulating unit synchronizes the phase P (0) and the first spreading code and despreads and demodulates the received signal with the first spreading code. The number of components in each of the first spreading code and the second spreading code is an integer greater than or equal to 2.

Abstract: An antenna holder for holding an antenna includes signal wiring and ground wiring being disposed on a single circuit board as either one of an external element and an internal element respectively with one end electrically coupled with a circuit on the single circuit board for serving as the external element in a spiral shape and the internal element inside of the external element at a predetermined distance. The antenna holder is provided with a spacer for keeping the predetermined distance between the external and the internal elements as well as an external tilt suppressor for suppressing a tilt of the external element from a direction being orthogonal to the circuit board.

Abstract: A first trigger unit and a second trigger unit output trigger signals to transceivers disposed for the four wheels of a vehicle. The first and second trigger units are attached to wall surfaces of tire housings corresponding to the left front and left rear wheels respectively. Each of the first and second trigger units is arranged in a position of the wall surface having an angle from 5 to 25 degrees with respect to the side of the corresponding wheel. Transceivers attached to a right front and right rear wheels are thus located farther from the trigger units than the left front and left rear wheels, respectively. Such arrangement allows the transceivers attached to the right front and right rear wheels to receive the outputted trigger signals with sufficient accuracy due to high field strength.

Abstract: An antenna includes outer and inner elements, one of which is a signal line and the other of which is a ground line. Each of the outer and inner elements is a helical element having helical portions. The inner element is arranged inside the outer element such that the outer and inner elements are spaced from each other. An axis of the outer element is parallel to that of the inner element.

Abstract: In a wheel identifying apparatus, first and second devices respectively transmit first and second trigger signals. The first device is mounted on the body of a vehicle closer to the front axle than the rear axle and closer to one of the front wheels than the other; it has the same height as the front axle and an orientation angle in a range of 0 to 90°. The second device is mounted on the vehicle body closer to the rear axle than the front axle and closer to one of the rear wheels than the other; it has the same height as the rear axle and an orientation angle in a range of 0 to 90°. Consequently, the first trigger signal can be reliably received by transceivers on the front wheels, and the second trigger signal can be reliably received by transceivers on the rear wheels.

Abstract: An in-vehicle LF transmitter transmits a synchronization signal to an in-vehicle RF receiver and transmits LF data (response request) including a synchronization signal to a portable device. The portable device performs RF data output and DSSS process and transmits RF data (response) subjected to spread process. The in-vehicle RF receiver receives the RF data and performs despread process. Both of the spread process of the portable device and the despread process of the in-vehicle RF receiver are performed by the use of a spread code the period of which is adjusted based on the synchronization signal transmitted from the in-vehicle LF transmitter.

Abstract: An antenna apparatus includes a substrate having a GND pattern land and an electric power feed pattern land on a same surface, an outer element extending away from the land in a spiral shape, and an inner element extending along an axis of the outer element in a spiral shape with a space interposed between itself and the outer element. The outer element and the inner element of the antenna apparatus respectively serve as one of a signal line and a GND line, and are supported by a retainer member to have predetermined relationship on a land formation surface. The retainer member is made of dielectric body, and the two elements respectively have a surface mount portion at one end that is to be fixed onto the substrate with electrical connection to corresponding lands. The surface mount portions are formed substantially parallel to the land formation surface.

Abstract: A portable antenna device includes a circuit board having a ground pattern, an antenna including a spirally wound external element and a spirally wound internal element coaxially disposed inside the external element at a distance from the first element so that one of the external and internal elements forms a signal wire and the other forms a ground wire. The circuit board includes plural passive elements each of which has a different impedance and a switch unit that selectively connects the antenna with the ground via one of the passive elements to provide a resonance characteristic of radio wave that has a frequency deference from a resonance characteristic provided by any other passive element.

Abstract: In a tire inflation pressure detecting apparatus according the invention, a second transceiver provided on the body of a vehicle changes operation thereof alternatively between a second transmitter and a second receiver mode, thereby intermittently transmitting a radio wave. A first transceiver provided on a wheel of the vehicle operates in a first receiver mode to receive the radio wave, thereby charging a charging unit. When the charging unit has been sufficiently charged, the first transceiver changes operation thereof from the first receiver mode to a first transmitter mode, in which the first transceiver first repeatedly transmits an informing signal at predetermined time intervals for a predetermined time period and then transmits a pressure signal. When the informing signal is received by the second transceiver in the second receiver mode, the second transceiver keeps the operation thereof in the second receiver mode until the pressure signal is completely received thereby.

Abstract: A batteryless tire inflation pressure detecting apparatus includes, on the body of a vehicle, antennas and a transmitter transmitting radio waves through the antennas. The apparatus also includes, on each wheel of the vehicle, a pressure sensor sensing the pressure of a tire, a transceiver, and a charging unit powering the pressure sensor and the transceiver. The charging unit is charged with electric power induced by a corresponding one of the radio waves received by the transceiver. The apparatus further includes, on the body of the vehicle, a receiver receiving pressure signals transmitted by the transceivers, a pressure determiner determining the pressures of the tires based on the pressure signals, and a controller. To minimize influence of the radio waves on neighboring devices, the controller controls the transmitter so that least two of the radio waves are transmitted at different times, or at the same with a phase difference therebetween.