Abstract: A communication system includes: a master device; and slave devices communicating with the master device via a transmission line. The master device includes: an electric power supply unit for outputting an electric power supply signal having one specific frequency to the transmission line; a master communication unit for communicating with each slave device through a communication signal; and an electric power supply frequency setting unit for setting the one specific frequency. Each slave device includes: an electric power supply signal input and output unit for retrieving the electric power supply signal having a set frequency from the transmission line; a communication signal input and output unit for receiving and transmitting the communication signal to the transmission line; a slave communication unit for communicating with the master device through the communication signal; and a power source for energizing the slave communication unit according to the electric power supply signal.

Abstract: In a communication system, nodes are coupled to a transmission path in a bus topology. The nodes communicate with each other via the transmission path using communication signals that have a communication frequency and are synchronized with a power supply signal. Each of the nodes includes a coupling portion that transmits and receives the communication signal and the power supply signal using electromagnetic induction in non-contact with the transmission path. Each of the nodes determines whether a collision of the communication signals occurs on the transmission path based on a voltage level of a signal that has the communication frequency and is induced at the coupling portion.

Abstract: In a power line communication system, a master uses a twisted pair wire as a power line and a communication line and outputs a power signal and a data modulation signal to a slave. The slave includes an aperture antenna, a power monitoring portion, and a determining portion. The aperture antenna receives the power signal via the twisted pair wire by electromagnetic induction coupling of an electromagnetic field generated at the twisted pair wire in accordance with an applied current of the twisted pair wire. The aperture antenna has an aperture region facing an aperture region between twists of the twisted pair wire. The power monitoring portion monitors a power of the power signal received via the first aperture antenna. The determination portion determines whether to use another operation power received via the twisted pair wire on the basis of the power monitored by the power monitoring portion.

Abstract: In an antenna device, a first helical part of a first antenna and a second helical part of a second antenna is disposed in a dielectric body on a ground plane. Each helical part is helically wound up in a direction perpendicular to the ground plane and includes a plurality of one-turn portions. Each one-turn portion of the first helical part has a peripheral length of M times a wavelength ? of use, where M is a positive natural number. One of the one-turn portions of the second helical part closest to the ground plane has a peripheral length Ks that is N times the wavelength ? of use, where N is a positive natural number greater than M. One of the one-turn portions of the second helical part farthest away from the ground plane has a peripheral length Ke, and (M·?)<Ke<Ks(=N·?).

Abstract: In a wireless communication system, a portable device transmits a first signal spread based on a reference period indicated by a synchronization signal transmitted from an in-vehicle device and transmits a second signal spread based on an operation by a user. The in-vehicle device sets a search period based on a variation range in a delay time from when the synchronization signal is transmitted to when the spread first signal is transmitted and sets a residual period that starts at an ending point of the search period and ends at an ending point of the reference period when a starting point of the reference period is set at a starting point of the search period. When the in-vehicle device fails in a synchronous acquisition for the search period, the in-vehicle device performs a synchronous acquisition process for the residual period.

Abstract: In a wireless communication apparatus, when a first switch electrically connects a second antenna to an impedance matching circuit and a second switch electrically connects a first antenna to a reception circuit, a frequency signal output from an oscillator of the reception circuit is received by the second antenna and applied to the impedance matching circuit. Then, a controller controls the impedance of the impedance matching circuit so as to bring a RSSI voltage output from a signal strength detection circuit of the reception circuit into agreement with a reference RSSI voltage, thereby bringing the reference frequency of the first antenna into agreement with a reference frequency.

Abstract: A wireless communication system has an in-vehicle system disposed in a vehicle and a portable device carried by a user, where the in-vehicle system and the portable device are communicably coupled. The in-vehicle system uses a transmitter for transmitting a request signal to the portable device in LF wave band, and the transmitter includes: a spread process unit for spread-modulating predetermined LF data by a spread spectrum method and for generating a spread data signal; and a modulation driver unit for converting the spread data signal to a modulation signal in the LF wave band and for outputting such modulation signal as a request signal to an antenna after amplifying the modulation signal.

Abstract: A matching circuit, connected to a receiving antenna and to the input of a receiving circuit, incorporates a variable capacitor that is adjustable for tuning the resonance frequency of the antenna to a desired reception frequency. In an automatic tuning mode of operation, an oscillator signal of different frequency from the reception frequency is applied to induce resonance of the antenna and matching circuit, and the variable capacitor is adjusted until an output signal level from the receiving circuit attains a predetermined value which has been stored beforehand in a memory and which corresponds to a condition whereby the antenna resonance frequency corresponds to the reception frequency and impedance matching exists between the antenna and receiving circuit.

Abstract: An onboard apparatus control system is disclosed. The onboard apparatus control system includes a portable apparatus and an in-vehicle apparatus which controls an onboard apparatus according to position of the portable apparatus. From multiple transmitting antennae, the in-vehicle apparatus transmits pulse pattern signals with different transmission frequencies at an overlapping timing, so that the pulse pattern signals are radio waves whose intensities are changed stepwise according to different patterns. The portable apparatus receives the radio waves transmitted from the multiple transmitting antennae. The position of the portable apparatus with respect to the vehicle is determined based on a combined pattern of the received pulse pattern signals, which a receiving unit is to receive at location with respect to the vehicle.

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: 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: 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 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 apparatus, when a first switch electrically connects a second antenna to an impedance matching circuit and a second switch electrically connects a first antenna to a reception circuit, a frequency signal output from an oscillator of the reception circuit is received by the second antenna and applied to the impedance matching circuit. Then, a controller controls the impedance of the impedance matching circuit so as to bring a RSSI voltage output from a signal strength detection circuit of the reception circuit into agreement with a reference RSSI voltage, thereby bringing the reference frequency of the first antenna into agreement with a reference frequency.

Abstract: A matching circuit, connected to a receiving antenna and to the input of a receiving circuit, incorporates a variable capacitor that is adjustable for tuning the resonance frequency of the antenna to a desired reception frequency. In an automatic tuning mode of operation, an oscillator signal of different frequency from the reception frequency is applied to induce resonance of the antenna and matching circuit, and the variable capacitor is adjusted until an output signal level from the receiving circuit attains a predetermined value which has been stored beforehand in a memory and which corresponds to a condition whereby the antenna resonance frequency corresponds to the reception frequency and impedance matching exists between the antenna and receiving circuit.

Abstract: In a filter circuit, first and second coils are connected to first and second communication lines, respectively. At a secondary side of the first and second coils, first and second capacitors are connected in series between the first and second communication lines. At a primary side of the first and second coils, third and fourth capacitors are connected in series between the first and second communication lines. A connection node between the first and second capacitors is grounded. A connection node between the third and fourth capacitors is grounded. The first and second coils are adjacently arranged in order to have a reversed polarity to each other. The filter circuit having the above structure works as a n-type filter capable of eliminate both common mode noise and normal mode noise. The filter circuit can eliminate noise caused by the first and second coils.

Abstract: In an antenna device, a first helical part of a first antenna and a second helical part of a second antenna is disposed in a dielectric body on a ground plane. Each helical part is helically wound up in a direction perpendicular to the ground plane and includes a plurality of one-turn portions. Each one-turn portion of the first helical part has a peripheral length of M times a wavelength ? of use, where M is a positive natural number. One of the one-turn portions of the second helical part closest to the ground plane has a peripheral length Ks that is N times the wavelength ? of use, where N is a positive natural number greater than M. One of the one-turn portions of the second helical part farthest away from the ground plane has a peripheral length Ke, and (M·?)<Ke<Ks(=N·?).

Abstract: In a wireless communication system, a portable device transmits a first signal spread based on a reference period indicated by a synchronization signal transmitted from an in-vehicle device and transmits a second signal spread based on an operation by a user. The in-vehicle device sets a search period based on a variation range in a delay time from when the synchronization signal is transmitted to when the spread first signal is transmitted and sets a residual period that starts at an ending point of the search period and ends at an ending point of the reference period when a starting point of the reference period is set at a starting point of the search period. When the in-vehicle device fails in a synchronous acquisition for the search period, the in-vehicle device performs a synchronous acquisition process for the residual period.

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 antenna apparatus includes: a ground substrate; and a loop antenna having first and second polarized wave surfaces, which are perpendicular to the substrate. The substrate provides an antenna, which is excited and vibrated together with the loop antenna. The antenna has a first polarized wave component in parallel to the first polarized wave surface and a second polarized wave component in parallel to the second polarized wave surface. A polarized wave ratio between the first polarized wave component and the second polarized wave component in the substrate is substantially equal to a polarized wave ratio between the first polarized wave surface and the second polarized wave surface in the loop antenna.