Showing papers by "NEC published in 1986"

Guarded horn clauses

Abstract: A set of Horn clauses, augmented with a ‘guard’ mechanism, is shown to be a simple and yet powerful parallel logic programming language.

Satellite communication system with random multiple access and time slot reservation

Abstract: A multiple access data communication system is disclosed wherein a communication channel is shared by a plurality of stations. The channel is divided into frames each being partitioned into time slots smaller in number than the number of stations of the system. A reservation status signal is constantly broadcast at frame intervals from a central station to all remote stations to indicate reserved status of the time slots. When a transmission request is made in a remote station, it discriminates a message signal shorter than the time slot length as a single packet having a time slot length and detects an idle time slot from the channel using the reservation status signal. If the message signal is longer than the time slot length, the station divides it into a series of packets of the time slot length and transmits a reservation request to the central station to receive from it a time-slot assignment signal and inserts the long-message packets to time slots specified by the time-slot assignment signal.

Multipoint communication system having polling and reservation schemes

Abstract: In a multipoint communication system, first polling signals are sequentially and respectively transmitted to terminal stations on a broadcast channel from a central station, asking a request for reservation without waiting for a reply from the terminal stations. A reservation signal is transmitted on a multiple access channel from a terminal station requesting the reservation to the central station in response to the first polling signal addressed to it. A second polling signal is then transmitted on the broadcast channel in response to the reservation signal and the multiple access channel is reserved for a period of time variable in accordance with the reservation signal. A data signal is transmitted from the terminal station requesting the reservation on the reserved multiple access channel in response to the second polling signal.

Horn antenna with a choke surface-wave structure on the outer surface thereof

Abstract: A horn antenna for radiating or receiving a microwave is provided with a plurality of axially spaced radial fins fixedly mounted on the outer surface of the horn, which fins form a plurality of radial grooves and a front axial groove each having a depth of approximately equal to a quarter of a wavelength of the microwave. Those fins and grooves form a choke surface-wave structure which improves the radiation pattern and reduces undesired radiation and side lobe. A multimode horn arrangement for a higher frequency wave is employed for the horn so that two different frequency waves are efficiently radiated or received at a single horn antenna with a reduced side lobe and an excellent cross polarization characteristic.

Advanced Groupband Data Modem Using Orthogonally Multiplexed QAM Technique

Abstract: An advanced groupband data modem based on the orthogonally multiplexed QAM technique is proposed. Its performance is evaluated through experiments. In the proposed modem, data are transmitted by a number of orthogonally multiplexed parallel subchannels. Because of this orthogonally multiplexing parallelism, the proposed modem becomes more immune to Gaussian noises, impulsive noises, and channel distortions, compared to the conventional Class IV partial response VSB modem. Furthermore, the orthogonally multiplexed QAM modem retains high flexibility in multiplexing a variety of data terminals and in carrying out fallback operation to a wide range of data rates. Experimental results demonstrate the robustness of the proposed groupband data modem.

Modulation system capable of improving a transmission system

Abstract: In a modulation system responsive to a system input signal for supplying an amplifier having nonlinearities with a modulated analog signal to make the amplifier produce an amplified output signal, the system input signal conveys a baseband signal having a predetermined sampling rate for reproduction and is sampled into a sequence of sampled signals having a specific rate higher than the predetermined sampling rate. The sampled signal sequence is converted by a random access memory into a sequence of predistorted signals which compensate for the nonlinearities and which are modulated into the modulated analog signal. Each predistorted signal is adaptively modified at the specific rate with reference to the sampled signals and an additional input signal derived from the amplified output signal. When the sampled signal sequence is sampled at the predetermined sampling rate, the predistorted signal sequence may be produced by interpolating each of the sampled signals at the specific rate. The baseband signal may be either a digital signal or an analog one.

Optical head comprising a diffraction grating for directing two or more diffracted beams to optical detectors

Abstract: For use in combination with an optical source for generating a coherent beam along a main optical axis, an optical head device comprises a diffraction grating having a plurality of grating regions which are responsive to the coherent beam for directing a zeroth-order diffracted beam to a focussing lens and are responsive to an optical beaem reflected from an optical recording medium for directing sidewards diffracted beams to an optical detector assembly. An effective area of a diameter of about 5 mm is sufficient for the diffraction grating. Each sidewards diffracted beam may form an angle of 20° with the main optical axis. The optical detector assembly is used in detecting focussing and tracking errors for the recording medium and can be used in reproducing optical information from the recording medium. A six-partitioned optical detector assembly is preferred when the grating regions are four in number. Either a four-partitioned or a three-partitioned optical detector assembly is preferred when the grating regions are two in number. Depending on the grating regions, the optical detector assembly preferably has two optical detector elements which are placed on different levels relative to the diffraction grating.

Mobile telephone system for automatically paging absent mobile subscriber

Abstract: A mobile telephone unit belongs to a mobile telephone system with a mobile telephone system (3) and a paging system (4) which cover an identical service area (8), are independently operated, and are connected through an exchange (2). The mobile telephone unit (5) includes a telephone set (5B) connected to a radio transmitter/receiver (5A) and an automatic pager calling circuit (10). The automatic pager calling circuit (19) includes a circuit (14,15,16,17) for detecting and storing that an incoming call is made for a mobile subscriber (6) who carries a pager (7) and is away from a vehicle, and a circuit (18,19) for sending a signal representing a preset pager number to the radio transmitter/ receiver (5A). The pager number signal from the radio transmitter/receiver (5A) is automatically sent by the paging system (4) to the pager (7) through the exchange (2), thereby calling the mobile subscriber.

An experiment on high-speed optical time-division switching

Abstract: An experimental high-speed optical time-division switching system has been realized. The system is able to exchange digitally encoded color video signals at 256-Mbit/s highway speed. Bistable laser diodes and directional coupler switch matrices are adopted as optical memories and optical read/write gates, respectively, in an optical time switch. The bistable laser diode operates as an optical flip-flop circuit which can be set and reset by optical and electrical signals, respectively. 256-Mbit/s highway speed has been realized with sufficient input highway operating margin using the same wavelength as that of bistable laser diodes for an electrooptical converter. Results of this experiment will be helpful data for use in constructing future optical telecommunications networks, where a variety of broad-band services need to be realized.

Light valve for use in a color display unit with a diffraction grating assembly included in the valve

Abstract: In a display unit for use in projecting projection light onto a screen to display a picture, a light valve comprises a diffraction grating assembly for selecting one of chrominance components included in an incident light given through one surface of the light valve The diffraction grating assembly is divided into a plurality of grating elements arranged to give different colors corresponding to the chrominance components In addition, a control beam, such as a laser, is incident onto the other surface of the light valve to selectively scan the grating elements and to heat selected ones of the grating elements through an energy converting film Thus, the incident light is subjected to modulation on the grating elements in accordance with heat energy and emitted through a liquid crystal as controlled light from the light valve The controlled light is sent as the projection light to the screen

High-speed packet-switched communications system with end-to-end flow control and retransmission

Abstract: Disclosed is a packet switched communications system wherein a plurality of switching nodes serves a plurality of terminals through transmission links. Each of the terminals transmits a packet of data-link layer control protocol including a network-layer control protocol to an associated one of the switching nodes. Each of the switching nodes is responsive to the network control protocol of the packet for routing it to one of the transmission links defined by the network layer control protocol of the packet. The switching node includes a plurality of line controllers associated respectively to the transmission links. Each line controller appends a physical address of the packet at the defined transmission link to the packet and updates its network-layer control protocol with a logical address of the packet at the defined transmission link and sends it to the line controller associated with the defined transmission link by way of a switching network.

One frequency repeater for a digital microwave radio system with cancellation of transmitter-to-receiver interference

Abstract: A digital microwave radio repeater using the same carrier frequency for the transmitting and the receiving carriers for improving the frequency utilization efficiency. The transmitter-to-receiver interference signal is cancelld by producing an estimated-interference signal of the interference signal from the digital baseband signal by the use of a transversal filter and by subtracting the estimated-interference signal from the received signal. The estimated-interference signal is also produced by frequency shifting a digital modulated signal in the transmitter. The transmitting carrier frequency is locked to the receiving carrier frequency by the use of a phase-locking technique, so that the interference signal is reduced.

Method of determining optimal transmission channel in multi-station communications system

Abstract: In order to effectively avoid cochannel interferences in a multi-station communications system utilizing a plurality of channels in common, the order of transmission channels to be used is determined utilizing a transmission priority assigned to each channel. The subject matter is characterized in that (a) the transmission priority of a selected channel is raised if the selected channel is not used at another station, and (b) is lowered if the selected channel is used at another station. This means that the past use records of the transmission channels are accumulated so that a good channel can be selected with high probability. In other words, a transmission channel with high priority is still ready to be used even if it was not selected in the preceding selection.

Mobile radio communications system

Abstract: A mobile radio communications system for wide area mobile radio communications allows any two remote mobile stations to hold communications by way of a public switching network. A fixed station governing an area in which a calling mobile station is located sends to a switching network its own identification (ID) data and ID data associated with a mobile station which is connected to the fixed station by radio. Based on the two kinds of ID data, a called mobile station sees a telephone number assigned to the calling mobile station and a telephone number assigned to the fixed station which is associated with the calling mobile station.

Channel switching system

Abstract: In a digital radio communication system using at least two regular channel and two or more standby channels for transmitting a test signal therethrough in the standby condition thereby permitting the regular channel to be synchronously switched to one of the standby channels, the improvement wherein a channel switching system for monitoring the standby channels is provided at the receiving side of the digital communication system with: control signal generator means operating so that when two or more standby channels are in standby condition, it generates a control signal to designate them in turn, and when only one standby channel is in standby condition, it generates a control signal to designate the channel; synchronizing switching means for selectively outputting the test signal transmitted via each of the standby channels designated by the control signal; and standby channel monitoring means for detecting an output from the synchronizing switching means to monitor the communication quality of the standby channel placed in standby condition on the basis of the result detected.

Routing method for use in wiring design

Abstract: A method for automatically designing the route of the wiring on printed wiring boards, large scale integrated circuit (LSI) chips or the like which can be used to create the wiring design of wiring boards or the like having a plurality of different wiring pattern densities.

Double heterojunction semiconductor device with injector

Abstract: A semiconductor device including a first semiconductor layer having a low carrier density, a second semiconductor layer on the first semiconductor layer and having a low carrier density, a third semiconductor layer on the second semiconductor layer, a fourth semiconductor layer on the third semiconductor layer and effective to inject holes into the second semiconductor layer through the third semiconductor layer for inducing a channel of, for example, electrons in the second semiconductor layer in proximity to and along the interface between the second and third semiconductor layers, and a pair of ohmic contact regions extending through the second and third semiconductor layers for providing ohmic contact with the second semiconductor layer for permitting modulation of the conductance between the ohmic contact regions when holes, for example, are injected from the fourth semiconductor layer into the second semiconductor layer. The device has double heterojunctions, one between the first and second semiconductor layers and the other between the second and third semiconductor layers, thus providing FET mode and bipolar mode of operation.

Linear motor driving device

Abstract: A linear motor driving device includes a pair of actuators each having a first piezoelectric element, a pair of levers connected to the first piezoelectric element, and an apparatus for magnifying the displacement caused by the first piezoelectric element. A second piezoelectric element is connected to the pair of actuators. The second piezoelectric element translates the levers in a direction perpendicular to the direction of actuation of the levers.

Semiconductor laser module

Abstract: The disclosure describes a semiconductor laser module having a semiconductor laser and an optical fiber for guiding a laser beam which issues from the semiconductor laser to become incident to the optical fiber, comprising an optical fiber, having an end face which is included 3° to 10° relative to a plane which is perpendicular to an axis of the optical fiber, a transparent optical member having a first end face which is intimately engaged with the end face of the optical fiber and a second end face which faces of the first end face and is perpendicular to the axis of the optical fiber, the optical member being substantially the same in refractive index as a core of the optical fiber and extending over a predetermined length along the axis of the optical fiber, and a reflection preventing film provided on the second end face of the optical member, whereby the laser beam is inclined to the reflection preventing film with an optical axis of the laser beam extending perpendicular to the second end face.

Re-synchronization system using common memory bus to transfer restart data from non-faulty processor to failed processor

Abstract: A multi-processing device includes three or more processing systems, each having a processor and a corresponding main memory connected to each other by means of an individual memory bus. The multi-processing device also includes a common memory bus connectable to all the processors and all the main memories of the respective systems, an asynchronism detection circuit connected to the respective processors to produce an asynchronism detection signal indicating which system or systems are in asynchronous state, and a device control circuit responsive to the asynchronism detection signal to send a common memory bus select signal to the main memory of each failed system to change its bus connection from the individual memory bus to the common memory bus. The device control circuit also generates a master designation signal for allowing an arbitrary processor of the normal non-faulty systems to be designated as a master processor, and a copy request signal to the respective processors. The copy request signal causes the master processor to copy the content of the main memory of the normal system to the main memory of each failed system. When the synchronization between the respective systems is established, the device control circuit outputs a restart request signal to the respective processors, thus initiating the execution from a fixed, stored address in a control memory of each processor to enable synchronous starting of all of the processor. The multi-processing device further includes a communication control circuit connected to the common memory bus, thus permitting parallel loading of an initial program to the main memories of the respective systems for achieving recovery in the case where all the systems are asynchronous with each other.

Semiconductor memory device having serial writing scheme

Abstract: An improved semiconductor memory which can achieve high-speed data processing is disclosed. The memory comprises a memory array, a random access port for accessing a desired one of memory cell in accordance with row and column addresses, a serial read circuit for consecutively reading data from the selected row one by one and a serial write circuit for consecutively writing data to the selected row one by one without specific column address information.

Method of manufacturing ceramic electronic device

Abstract: A method of manufacturing a ceramic electronic device includes the steps of: forming a pattern of a predetermined shape made of a photosensitive resin; forming an electrical circuit element on a ceramic green sheet; stacking and pressing the pattern, the ceramic green sheet having the electrical circuit element thereon, and at least one ceramic green sheet to prepare a laminated body; and sintering the laminated body. A ceramic electronic device integrally including a cavity and the electrical circuit element therein is manufactured by this method.

Mechanical Stress Dependence of Radiation Effects in MOS Structures

Abstract: The effects of mechanical stress on radiation damage in polycide-gate MOS capacitors have been investigated as a function of gate-oxide thickness and silicide-gate electrode material (TiSi2, MoSi2 and WSi2). It was found that compressive stress on the SiO2/Si interfacial region reduces both positive charge build-up and interface-trap generation. The positive charge build-up exhibits a smaller stress effect, as compared with the interface-trap generation. The magnitude of stress effect depends only on the compressive strength, and not on the silicide material, if the annealing conditions are the same. In addition, as the gate-oxide thickness decreases, the stress effect on positive charge build-up increases, while the interface-trap generation remains nearly constant. These results can be explained on the basis of the bond reformation process, i. e., in a region where compressive stress exists, the broken bonds are reformed with high probability. Futhermore, radiation response of MOS transistors with different gate-oxide stress values have been evaluated, and compared with those observed in MOS capacitors. Similar stress effects were also obtained.

Diversity reception radio receiver

Abstract: A diversity reception radio receiver has a two-receiver system incorporating first and second receivers. A wave envelope detector is provided for each receiver to generate an output voltage corresponding to the strength of the electromagnetic signal wave which is picked up by the receiver. A hysteresis comparator compares the outputs of the two wave envelope detectors and generates a switching control signal. A switching device responds to the switching control signal by selecting between the signals which are repoduced by the first and second receivers. Because the amount of hysteresis in the comparator is automatically adjusted in accord with the strength of the signal wave, there is a minimum of hunting between the outputs of the two receivers.

Method and arrangement of coding digital image signals utilizing interframe correlation

Abstract: In order to encode image signals using interframe correlation while maintaining high data compression as well as high resulting images, a motion compensated interframe prediction error is orthogonally transformed and then is subject to quantization. Thereafter, the quantized error signal undergoes inverse orthogonal transformation. In order to compensate for distortions caused by the quantization, a difference between the inversely orthogonally transformationed error signal and the original prediction error signal is quantized. By selecting the quantization characteristics, the influence or contribution of the orthogonal transformation can be controlled continuously.

A simple method to evaluate device lifetime due to hot-carrier effect under dynamic stress

Abstract: A method to evaluate hot-carrier-induced NMOSFET degradation under dynamic stress is discussed, based on an empirical relation between device lifetime and substrate current in static stress. The device lifetime τ under dynamic stress is given by \tau = A.I_{sub,peak}^{-2.5}/R , where I_{sub,peak} is the peak value of pulsive substrate current and R is its duty ratio. The device lifetime experimentally obtained in an inverter circuit is in good agreement with the calculation results obtained from the proposed method. This method is useful to estimate device lifetime in actual circuit operational conditions.