Showing papers by "NEC published in 1987"

Antireflection effect in ultrahigh spatial-frequency holographic relief gratings.

Abstract: An interpretation model for low reflectivity in ultrahigh spatial-frequency holographic relief gratings is proposed. The model is based on the concept that the grating effective index, caused by grating ultrahigh spatial frequency, is graded in the depth direction and forms an antireflective constitution similar to the multilayer coating. Numerical results show that a sinusoidal grating is antireflective over wide groove depth, wavelength and incident angle ranges, and a grating with nearly triangular section, having a circle arc index distribution, has a very low reflectivity, >10(-4)%. Reflectivity vs groove depth, obtained experimentally for a holographically recorded photoresist grating, agrees fairly well with the numerical results.

Compensation of soliton broadening in nonlinear optical fibers with loss

Abstract: A novel optical fiber is proposed that supports the lowest-order soliton despite the presence of optical loss. Group-velocity dispersion of this fiber decreases with distance, in accord with soliton attenuation that is due to the inherent optical loss of the fiber.

Multilayer wiring substrate

Abstract: A multilayer wiring substrate wherein a substrate of ceramic material (11) contains a plurality of power supply wiring layers (1) and is formed with first and second through-holes (20,20a) Each of the first through-holes (20) contains a first metal layer (32,33) which is connected to at least one of the power supply wiring layers (12,13) Each of the second through-holes (20a) has a wall surface coated with a layer of a fluoride resin dielectric (21) with a second metal layer (22) formed on the coating A circuit is supplied with power via the first metal layers and with signals via the second metal layers The circuit comprises thin film wiring layers (25) formed on the substrate, insulating layers (24) made of an organic material, and electronic circuit elements (not shown) The substrate is made by coating upper and lower surfaces and through-holes of a substrate with a layer of the fluid resin dielectric, removing the coating from the upper and lower surfaces, forming a metal layer in the upper and lower surfaces and on the coating and removing the metal layer except for portions at each end of and within the through-holes

Highly Efficient Digital Mobile Communications with a Linear Modulation Method

Abstract: Although linear modulation methods can achieve high spectrum efficiency, very little attention has been directed to their use in mobile radio systems. This is mainly due to the fact that the nonlinearity of the transmitter power amplifier tends to spread the spectrum and thus eliminate any spectrum efficiency advantage gained through the use of linear modulation methods. In this paper, a linear modulation system is proposed, which solves the above difficulty and which gives higher spectrum efficiency than conventional digital FM. The modulation/demodulation method is \pi /4 shift QPSK and phase-shift detection with a limiter-discriminator and an integrate-and-dump filter. By introducing a cartesian coordinate negative feedback control, 35 percent power efficiency at 10 W output power and - 60 dB relative out-of-band radiation are simultaneously achieved with a class "AB" amplifier, owing to the 29 dB feedback gain. The receiver configuration is easy to realize and gives immunity against fast fading through the use of noncoherent detection with limiter-discriminator. By using a novel decision method, bit error rate performances under both nonfading and fading condition are comparable to those obtained by digital FM. These results make it possible for linear modulation methods to achieve higher spectrum efficiency than is possible with conventional digital FM methods in mobile radio communications.

Method for driving a CCD area image sensor in a non-interlace scanning and a structure of the CCD area image sensor for driving in the same method

Abstract: The invention provides a method for driving a CCD area image sensor. An interline transfer type CCD area image sensor includes a plurality of photo sensors arranged in a plurality of lines. A plurality of vertical shift registers are disposed along one of the lines of photo sensors. A horizontal shift register is formed to receive charges from the vertical shift registers. An output circuit converts the charges transferred through the horizontal shift resistor into electrical signals. The driving method includes the steps of accumulating charges in the photo sensors, transferring charges accumulated in all of the photo sensors to the vertical shift registers, and shifting the transferred charges to the horizontal shift register via the vertical shift registers. The start of charge-shiftings is initiated from the charges in the order of the distances between the transferred position and the photo sensors and the horizontal shift register. The charges received from the vertical shift registers are shifted through the horizontal shift register to an output circuit where the quality of charges reaching the output is converted into an electrical signal. The CCD area image sensor includes at least one shift register circuit for producing shift pulses which perform the above-mentioned operations.

Over 720 Ghz (5. 8nm) frequency tuning by a 1.5 μm DBR laser with phase and Bragg wavelength control regions

Abstract: A 15 μm distributed Bragg reflector (DBR) laser with phase and Bragg wavelength control regions was newly developed Over 720 GHz (58 nm) continuous frequency tuning with 2mW light output were achieved for the first time

Separation of Small Particles Suspended in Liquid by Nonuniform Traveling Field

Abstract: A study of size and charge-dependent separation of small particles in liquid using a traveling-field-type electric curtain device is made. The principle of the separation is to make use of the spatial harmonic components of the rotating traveling field produced by such a device, the first harmonic propagating in one direction, which plays a dominant role in the region distant from the electrodes, and the second harmonic propagating in the opposite direction, which becomes dominant near the electrodes. Small particles brought into this field undergo circular motion and, as a result of field nonuniformity, are repelled from the electrodes and drift in the direction of the dominant harmonics. The lighter or more charged particles are strongly repelled from the electrodes and swept by the first harmonic, while the heavier or less charged particles can approach the electrodes and are transported by the second harmonic in the opposite direction, thus enabling separation by mass and charge. First a theoretical investigation of this method is made to clarify the operation conditions for the separation, then the experimental observations of particle motion are made and scaling laws of transport velocity with the applied voltage and frequency are confirmed. Finally, an example of a cell separator design using this method is presented.

Directional discrimination in the self-mixing type laser Doppler velocimeter.

Abstract: A simple and inexpensive method of directional discrimination of velocity based on the analysis of the Doppler signal's waveform obtained through a self-mixing type laser Doppler velocimeter (LDV) is described. The technique does not need the components commonly used to give the frequency offset required to yield directional information in LDV. The device is described, and experimental evidence is presented.

Radio communication system with power saving disablement prior to call handling processes

Abstract: A radio communication system comprises a base station for periodically transmitting a power saving signal and an information signal, a repeater station for relaying the signals, and a plurality of terminal stations for communicating with the base station through the repeater station. The repeater station includes power saving circuitry which responds to the power saving signal by cutting off power supplies to its major power consumptive components during a preset interval which alternates with an active interval during which power is supplied to the components. Each terminal station includes power saving circuitry responsive to the power saving signal relayed by the repeater station to cut off power suplied to its major power consumptive components during the preset interval and power saving disabling circuitry for transmitting a power saving disabling signal to the repeater station during the active interval in response to a request for call and disabling its power saving circuitry for the duration of the preset interval. The repeater station responds to the power saving disabling signal from a terminal station to disable its power saving circuitry for the duration of the preset interval to thereby permit the information signal to be relayed to the terminal station which has transmitted the power saving disabling signal. The terminal station then transmits a call request signal to the repeater station to permit it to be handled during the interval in which power saving is disabled.

Air cooling equipment for electronic systems

Abstract: An air cooling equipment for use in electronic systems having a plurality of wiring boards with a plurality of heat-generating electronic components mounted thereon is disclosed. The air cooling equipment uses two blowers positioned on top and bottom of the unit and introduces cooling air in two directions into the housing. The blowers may be positioned at sides of the housing and air is directed around and through the zone where the wiring boards are disposed.

A liquid crystal display device having display and driver sections on a single board

Abstract: A liquid crystal display device includes first board having a reference voltage electrode on one surface, a second board having, on a main surface, a lattice of conductive stripes, a plurality of pairs of a transistor and a picture element electrode, each pair being disposed at each crossing point of the conductive stripes and the transistors being thin film transistors using poly­crystalline or amorphous silicon, and a driving circuit for driving the conductive stripes, the driving circuit being formed in a monocrystalline silicon in a form of semiconductor integrated circuit directly connected to the conductive stripes, and a liquid crystal interposed between the one surface of the first board and the main surface of the second board.

Key distribution method

Abstract: A key distribution method and system for distributing a key over an insecure communication channel between first and second systems Both first and second systems generate respective random numbers, calculate key distribution codes based on that random number, public information and information secret to the respective systems, and transmits the distribution codes to the other system The same key is generated by both systems based on public information, the locally generated random number and the received key distribution codes Alternatively, the systems may exclude the secret information from the key distribution codes but generate and transmit identification codes based on the secret information, public information and the locally generated random numbers The received key distribution and identification codes are subjected to a known transformation and compared to known identification of the transmitting system

Cooling system for electronic equipment

Abstract: A cooling system for maintaining the temperature within electronic equipment has a circulation system for pumping a cooling liquid, such as water, through the electronic equipment where it picks up heat generated by the electronic equipment. The cooling liquid is pumped through a plurality of heat exchangers using a refrigerant which is, in turn, pumped through a compressor-condensor combination, each heat exchanger having approximately the same cooling capacity. A central control selects the number of heat exchangers which are to operate at any given time, on a basis of the differential in the temperature of the water being pumped into and out of the electronic equipment. This maintains a desired and relatively wide range of temperatures. A heating element selectively and controllably heats the cooled water to bring the wide range of temperatures to a selected and fixed temperature.

Routing method for use in wiring design

Abstract: A routing method for wiring design including a determining step for identifying, in one of the wiring sections where no wiring path is determined as yet, the direction of the line segment which is prohibited by an obstacle and accordingly determining a wiring path. The routing method also includes a generating step for generating, on a layer opposite to the layer on which one unprocessed line segment is present and in a position having the same plane coordinates as the line segment, an obstacle which prohibits only such line segments as are parallel in direction to the line segment, on the wiring path determined by the determining step.

Semiconductor laser device

Abstract: PURPOSE:To facilitate the registering of optical axes and to enable the length of a resonator to be freely designed, by providing a current injection electrode in a part of an element having a quantum well structure on a substrate so as to provide an active region, while utilizing the other part as an external resonator region capable of varying the length of the quantum well structure. CONSTITUTION:An N-type Al0.35Ga0.65As clad layer 12, a quantum well layer 13 consisting of a 300Angstrom thick Al0.3Ga0.7As, 100Angstrom thick GaAs and 300Angstrom thick Al0.3Ga0.7As, and a P-type Al0.35Ga0.65As clad layer 14 are deposited in that order on an N-type GaAs substrate 11 to form a double hetero structure. This double hetero structure having a 2mum wide stripe shape i filled up with an N-type Al0.35Ga0.65As filling layer 15 to form a semiconductor laser having a length of a resonator of 10mm. A Zn diffusion section 17 is provided from one end face of the laser up to 300mum therefrom, and an electrode 16 is vapor deposited on the section 17. In this construction, the Zn diffusion section 17 provides an active section 51 of the semiconductor laser and the other section provides an external resonator 52. Since the absorption loss in the external resonator 52 is decreased by the fact that light is waveguided through the quantum well layer 13, the resonator 52 can have increased dimensions. Thus, the distance between axial modes can be about 1GHz and an extremely short pulse having a width of 10ps can be obtained.

Instruction prefetching device comprising a circuit for checking prediction for a branch instruction before the instruction is executed

Abstract: In a data processing system capable of processing instructions under pipeline control in a plurality of stages including an executing stage, an instruction prefetching device comprises a prediction checking circuit (66, 67) coupled to a predicting circuit (52, 53) and an instruction executing circuit (32, 33, 37, 38) and a prefetch controlling circuit (47, 86) coupled to the predicting circuit and the checking circuit. In one of the stages that is prior to the executing stage, the checking circuit (66, 67) checks whether or not a prediction for a branch destination is correct. if the prediction is correct, prefetch is continued according to the prediction. If the prediction is an incorrect prediction, the prefetch is continued according to a correct prediction with the incorrect prediction corrected immediately after the executing stage. Check of the prediction may be for an instruction other than branch instructions, for either an unconditional branch instruction or a branch count instruction, for a branch destination address, or for a branch direction which becomes clear after the executing stage.

Thin film transistor array for liquid crystal display panel

Abstract: A thin film transistor array board includes an insulator substrate, a matrix of gate electrodes formed on the insulator substrate and covered with a gate insulator film, a matrix of semiconductor islands formed on the gate insulator film positioning on the gate electrodes, source wirings connected to the source regions of the semiconductor islands, drain wirings connected in common to the drain regions of the semiconductor islands aligned in the same line in parallel with the columns of the gate electrode matrix, a second insulator film covering the whole surface including the drain wirings, the source wirings, the semiconductor islands and the pixel electrodes, the second insulator film having grooves exposing the drain wirings and auxiliary wirings formed in the grooves in contact with the drain wirings.

CMOS integrated silicon pressure sensor

Abstract: The sensor described includes a four-arm piezoresistance bridge circuit, an amplifier, and a bridge excitation circuit This circuit is used to stabilize changes in sensitivity due to variations in temperature and supply voltage The sensor was fabricated using a self-aligned double-poly Si gate p-well CMOS process combined with an electrochemical etch-stop technique using N/SUB 2/H/SUB 4/-H/SUB 2/O anisotropic etchant for the thin-square diaphragm formation The silicon wafer was electrostatically adhered to a glass plate to minimize thermally induced stress Less than a /spl plusmn/05% sensitivity shift and less than a /spl plusmn/5-mV offset shift were obtained in the 0-70/spl deg/C range, with a 1-V/kg/cm/SUP 2/ pressure sensitivity By using a novel excitation technique, a sensitivity change of less than /spl plusmn/15% under a /spl plusmn/10% supply voltage variation was also achieved

Portable radio telephone having power saver

Abstract: A battery-powered portable radio telephone for use in a mobile telephone network receives signals from the network and judges from the received signal whether the radio telephone is inside or outside of the service area of the network. A battery saver is provided to periodically interrupt the battery power of the telephone when the latter is judged as being outside of the service area.

Read only semiconductor memory having multiple bit cells

Abstract: For precise read-out operation at an improved speed, there is disclosed a semiconductor memory device fabricated on a semiconductor substrate of a first conductivity type and including a plurality of memory cells, each memory cell comprising (a) an insulating film covering a surface portion of the semiconductor substrate, (b) a gate electrode formed on the insulating film and located over a channel forming region in the surface portion of the semiconductor substrate, a channel being produced in the channel forming region when the memory cell is selected, (c) a first impurity region having a second conductivity type opposite to the first conductivity type and formed in the surface portion of the semiconductor substrate, the first impurity region being contiguous to the channel forming region or spaced apart from the channel forming region depending upon a bit of information stored therein, and (d) a second impurity region of the second conductivity type formed in the surface portion of the semiconductor substrate, the second impurity region being contiguous to the channel forming region or spaced apart from the channel forming region depending upon a bit of information stored therein.

Paging receiver having battery saving circuit

Abstract: A paging receiver includes an improved battery saving circuit which reduces battery usage by powering the radio section and the waveform shaping circuitry only during intervals which include address codewords specific to the given receiver group. Power is not supplied during intervals containing synchronization code signals other than during the first such interval directly following the preamble code. Upon detecting a preamble code during said intervals, power is supplied continuously for a time period sufficient to encompass the synchronization code interval.

Mercury wetted contact switch

Abstract: A glass reed relay has an elongated glass enclosure with an electrode passing through and being sealed to each of the opposite ends of said enclosure. One of the electrodes has an associated reed for making and breaking contact with the other of said electrodes. The other electrode has a hollow tubular structure filled with mercury. The dimensions are such that only a limited amount of mercury can escape therefrom in order to wet the contacts without creating a pool of mercury.

Thin film magnetic head

Abstract: A thin film magnetic head has a layer of soft magnetic material formed on a substrate. The layer is formed into two yoke pieces and a magnetic return path, which form a gap at ends of the yoke pieces. The opposite ends of the yoke pieces are joined to the magnetic return path by overlaying magneto-resistive pieces to which an electrical bias is applied.

Method for forming a semiconductor device with trench isolation structure

Abstract: Formation of an integrated circuit device with the trench isolation process is disclosed. A plurality of circuit elements such as transistors are isolated from one another by trenches formed in field isolation regions of a semiconductor substrate. Each trench should be filled with appropriate materials to maintain the flatness of the surface of the substrate. Borophosphosilicate glass (BPSG) is employed as the material filled into each trench.

Optical transmitter comprising an optical frequency discriminator

Abstract: Supplied with an optical signal from a directly modulated semiconductor laser (11) in an optical transmitter, an optical frequency discriminator (15) converts a frequency modulated component of the optical signal to an intensity modulated component and produces an output optical beam which consists essentially of the intensity modulated component. Preferably, a negative feedback circuit (32, 33) is supplied in effect with the output optical beam representative of mark and space codes and controls the semiconductor laser and/or the optical frequency discriminator to keep the extinction ratio of the output optical signal at an optimum value such that the optical frequency discriminator has a transmissivity of about 90°/o for a predetermined one of the mark and space codes and a substantially zero transmissivity for the other of the mark and space codes.

Method of manufacturing a thin film transistor

Abstract: A method of manufacturing a thin film transistor comprises the steps of forming a gate electrode on one surface of a transparent substrate, forming on the substrate an insulating layer and a semiconductor layer in the named order to cover the gate electrode, and depositing a positive photoresist layer on the semiconductor layer. Thereafter, the photoresist layer is exposed by irradiating from the other surface of the substrate so as to use the gate electrode as a mask. Therefore, if the positive photoresist layer is developed, the unexposed portion remains on the semiconductor layer to correspond to the gate electrode. Then, the semiconductor layer is etched using the remaining photoresist as a mask so as to form a semiconductor island on the insulating layer, and source and drain electrodes are formed on the semiconductor island.

Semiconductor memory device

Abstract: A semiconductor memory device includes (a) a plurality of reference cells, (b) a plurality of memory cells, data stored in a selected reference cell among the reference cells being compared to data stored in a selected memory cell among the memory cells, (c) an address transition detector for detecting transition in input of addresses by which a memory cell is selected among the memory cells, and transmitting an address transition detecting signal indicative of the detected transition, (d) a counter for counting the address transition detecting signals, and (e) a reference cell decoder for selecting a reference cell among the reference cells in accordance with an output transmitted from the counter.

Key Distribution Systems Based on Identification Information

Abstract: Two types of key distribution systems based on identification information are proposed, one for decentralized networks and the other for centralized networks. The system suitable for decentralized networks is analogous to the Diffie-Hellman public key distribution system, in which the former uses each user's identification information instead of a public file used in the latter. The proposed system is able to defend the networks from impostors. The system suitable for centralized networks, which is less analogous to the Diffie-Hellman system, can also defend the networks from impostors, though the network center does not have any directory of public or private key-encrypting keys of the users. Both of the systems proposed in this paper do not require any seivices of a center to distribute work keys, or users to keep directories of key-encrypting keys. Therefore, key management in cryptosystems can be practical and simplified by adopting the identity-based key distribution systems.

Multipoint data communication with a supervisory system for detecting a malfunctioning remote station

Abstract: A random access multipoint data communication system comprises a central station and a plurality of remote stations. A multiple access channel is established from the remote stations to the central station and a broadcast channel is established from the central station to the remote stations. The central station generates a timing signal for causing each of the remote stations to define commonly shared time slots on the multiple access channel. Each remote station transmits data on a randomly determined time slot of the multiple access channel. The central station periodically and sequentially interrogates the remote stations to return an acknowledgment and processes the returned acknowledgements to determine the presence of a malfunctioning remote station. To avoid data collision, the central station specifies an idle time slot on which the interrogated remote station is requested to send the acknowledgment.