Abstract: A road vehicle communication method allows bothway communication to be held between a mobile station, which sends a request for an information service and receives it, and a central base station and local base stations located at a roadside for sending the information service to the mobile station. The central base station and the local base stations use optical fibers in part of the transmission path thereof for the bothway communication and perform at least one of electric-to-optical conversion and optical-to-electric conversion. The mobile station is caused to send the request for an information service beforehand. In response to the request, the local base station covering the mobile station expected to receive the information service is estimated. When the mobile station lies in a service area to which the local base station estimated is assigned, a control station is caused to provide the mobile station with information corresponding to the information service requested.

Abstract: A GPS receiver including a receiving portion for receiving a GPS signal, a PN code signal generator, a correlation detector including a reproduced carrier signal generator, and a phase difference detector is disclosed. A frequency and a phase of the reproduced carrier signal are controlled according to a correlation result to track the carrier signal in the GPS signal, the PN code signal generator generates the PN code with a phase thereof controlled by phase control data from the correlation result, and amplitudes of the GPS signal is repeatedly sampled at timings with a deviation from an edge of PN code signal from the PN code signal generator varied. A zero-cross point on the variation of the sampled amplitudes provides a phase difference. The total phase difference is derived by summing the phase control data and the phase difference. To more accurately detect the phase difference, an interpolation may be effected. The sampling timings may be collectively generated as a train of sampling signal.

Abstract: A demodulator circuit in which N satellite signals included in N radio waves transferred from N satellites are detected by removing noise codes and carrier waves modulated by the satellite signals and the noise codes from the radio waves to measure a position of a movable body is disclosed. N pseudo-noise code signals indicating pseudo-noise codes corresponding to noise codes peculiar to the satellites are generated in N pseudo-noise code generators, and N correlation signals indicating degrees of correlation between the radio waves and the N pseudo-noise code signals are generated in N correlation units. Therefore, the noise codes are removed from the radio waves. Also, M carrier oscillating signals corresponding to each of the carrier waves of the radio waves are generated in (N.times.M) carrier local oscillators, and the N correlation signals are frequency-converted into (N.times.M) base signals with the (N.times.M) carrier oscillating signals in (N.times.M) orthogonal frequency converters.

Abstract: In a position measuring system, a position of a moving body is derived when data is sufficient for such derivation. On the other hand, when data is insufficient for such derivation, an area which may include the position of the moving body is derived. Accordingly, a user correctly evaluates reliability of information which is displayed. In a position measuring method, a measurement error of the derived position is evaluated. Further, a moving error evaluation is performed to evaluate an increase of the error. By changing the measurement error of the derived position, the area which includes the position of the moving body with high reliability can be displayed to the user.

Abstract: A method, for use in a receiver for the NAVSTAR global positioning system (GPS), of deriving successive values of phase of a received pseudo-random code signal following a momentary interruption of satellite signal reception, with the effects of signal noise eliminated by averaging processing, by first setting a replica pseudo-random code signal to an initial phase value which provides high correlation with the received code signal, and thereafter periodically executing phase derivation operations to obtain the phase of the received code signal, by obtaining the phase difference between the received and replica code signals, obtaining the average value of all of such phase differences obtained up to that point since the initial phase derivation operation, and adding that average value to the sum of a phase value obtained in the first phase derivation operation and a total estimated amount of change of phase of the received code since that first operation.

Abstract: A GPS receiver comprising a pseudonoise generator for simultaneously generating pseudonoise signals respectively corresponding to satellite electromagnetic waves transmitted from two or more satellites, an oscillator for simultaneously regenerating carrier waves of the plurality of satellite electromagnetic waves, and a plurality of demodulators responsive to the regenerated carrier waves and the pseudonoise signals to demodulate individual satellite electromagnetic waves independently, to thereby regenerate data transmitted from individual satellites, each demodulator being operative, during demodulation, to detect a set of phases of one pseudonoise signal and one regenerated carrier wave relative to one satellite electromagnetic wave on time division basis and including a first mixer for mixing of one pseudonoise signal, a second mixer for mixing of one regenerated carrier wave and a filter, whereby a set of phases of one pseudonoise signal and one regenerated carrier wave is changed to another set at timed

Abstract: A diversity receiver provides plural antennas, one receiving part for receiving the radio wave from one of the plural antennas and a control part for selecting one antenna from the plural antennas, wherein the antenna is selected in a manner that an antenna receiving the most intensive radio wave is detected by switching of the plural antennas in-turn in a time period T.sub.1, and the detected antenna is selected for receiving an information of the radio wave in a time period T.sub.2, the plural antennas may be disposed with distances shorter than a wavelength of the radio wave.

Abstract: A digital signal processing apparatus is shown which is applicable for real time operation in the power spectrum of the detected outputs of ultrasonic Doppler blood flowmeter. The apparatus comprises a digital operating means, a memory means which is connected to said digital operating means to transfer data thereto and receive data therefrom, a fixed instruction generating portion for generating operating code for the digital operating means and addresses for the memory means, a read only memory for storing data of a squaring operation which has address inputs at the bit position selected as most suitable from the input data bus line of said digital operating means, an overflow detecting means when input data exceeds the region of the address input, and digital saturation circuit, whereby the power spectrum can be calculated by fundamental algorithm of WFTA having a smaller number of operating steps than algorithm FFT.

Abstract: An ultrasonic wave blood flow meter comprises a probe which sends to and receives an ultrasonic wave reflected with Doppler effect from the blood flow, a detecting circuit for converting a frequency variation of the received reflected wave into a first signal whose amplitude varies with frequency and a second signal whose amplitude is kept constant, and first and second effective-value detecting circuits for obtaining d.c. components of the first and second signals. A level discrimination circuit is further provided for discriminating the level of the d.c. component detected by the second effective-value detecting circuit. First and second sensitivity-variable amplifiers are also provided for varying their sensitivities in accordance with the result of the level discrimination circuit. A dividing circuit divides the d.c. component amplified by the first sensitivity-variable amplifier by the d.c.

Abstract: Ultrasonic echo signals are detected in phase and integrated with a period corresponding to an ultrasonic pulse. The integrated values are sampled and the difference between two integrated values is successively frequency-analyzed.

Abstract: An ultrasonic imaging system comprises a transducer array including a plurality of elongated piezoelectric transducers successively arranged along a curved surface for emission of diverging beams of acoustic energy and an acoustic diverging lens affixed to the curved surface for increasing the angle of divergence of the emitted acoustic energy. The system includes a source for successively generating burst energy and means for selectively establishing a connection from the energy source to a subarray of the transducers to transmit a beam of acoustic energy therefrom and shifting the connection to the next subarray by at least one transducer in response to the generation of subsequent acoustic energy to cause the emitted acoustic energy to be angulated in an arc scan format. Means are provided for compensating for differences in energy level resulting from the differences in the path-length of the acoustic lens.

Abstract: An ultrasonic transducer array for arc scan imaging systems comprises a plurality of elongated piezoelectric transducers arranged successively to define a convexed energy radiating surface. A plano-concave acoustic diverging lens is attached to the convexed surface to diverge the acoustic energy transmitted from the transducers in an increased steering angle. The transducers are assembled on an impedance matching layer which defines the convexed radiating surface. The acoustic impedance of the diverging lens is substantially equal to the acoustic impedance of the human body, while the acoustic impedance of the impedance matching layer is greater than that of the human body.

Abstract: Ultrasonic echo signals are successively sampled and converted to digital echo data which are written into a first digital memory column by column and then read out row by row into a first buffer memory. The digital echo data which are derived in response to beams successively transmitted in a predetermined direction are written into columns of a second digital memory and read out of the memory in rows into a second buffer memory. The data stored in the first and second buffer memories are read out for digital-to-analog conversion and selectively applied within a television "frame" interval to control electron beam intensity of a single cathode ray tube so as to present tomographic and cardiographic images in different display areas of the tube.

Abstract: An ultrasonic imaging system includes a linear array of transducers of which a group of successively arranged transducers is selected and successively shifted to the next by at least one transducer. The transducers of the selected group are successively activated at respective delay times to transmit a radial scan beam which appears to emanate from a hypothetical point source located behind the transducer array. A scan converter is provided for conversion of analog echo signals in sector scan format to digital echo data in raster format for visual display.

Abstract: A sector scan ultrasonic imaging system comprises a source of a plurality of square wave pulse trains each being delayed by a unit quantization time with respect to adjacent trains, and a plurality of transmitter circuits corresponding to the elements of a transducer array. The duration of each square wave pulse is an integral multiple of the unit quantization time interval. Each transmitter circuit includes a read only memory in which a set of different digital delay time data is stored for the corresponding transducer element and is arranged to be retrieved in response to each angle increment of the ultrasonic beam transmitted from the array. Further included are a data selector for selecting a pulse train in response to a pulse train selection data retrieved from the memory and a programmable counter for counting the pulses of the selected train to generate an output in accordance with a pulse selection data retrieved from the memory.

Abstract: A focusing circuit for focusing an array of transducers of an ultrasound imaging system includes a variable delay line comprising a plurality of summing amplifiers and a plurality of variable delay elements provided between successive summing amplifiers. A plurality of switches is provided for respectively connecting the transducers to selected summing amplifiers. The amount of delay of each variable delay element is individually controlled so that the corresponding electrical signals derived from the transducers arrive in phase at the output end of the variable delay line.

Abstract: A scan converter is disclosed for use in a sector scan type ultrasound imaging system in which ultrasound echo signals return from targets along a plurality of radial scan lines distributed in a sector field with a substantially equal tangential angular increment with respect to a reference line. The scan converter comprises a sampling circuit which samples the echo signals at a speed inversely proportional to the cosine of the angle of deflection of the radial scan lines with respect to the reference line so that the sampled points align themselves in lateral lines perpendicular to the reference line. The sampled echo signals are converted into digital echo data and stored in a random access memory in the direction of its columns. The stored data are retrieved serially in the direction of the rows and fed into an interpolator for making interpolations between the successively retrieved echo data.