Showing papers by "NEC published in 1989"

Linear amplification technique for digital mobile communications

Abstract: The author proposes a novel predistortion linearizer which can meet the power-amplification requirements of digital mobile radio systems with high power efficiency and low out-of-band emission. This method can be used for narrowband mobile radio systems. It has been shown that the linearizer can achieve low-out-of-band emission under frequent changes of the amplifier nonlinearity. It is indicated that the hardware volume and the power consumption can be reduced sufficiently to make this predistortion linearizer applicable to mobile station transmitters. Nearly -60dB out-of-band emission and 33% power efficiency were obtained, which is comparable to corresponding results for a class C amplifier. >

High-performance TFTs fabricated by XeCl excimer laser annealing of hydrogenated amorphous-silicon film

Abstract: High-performance staggered a-Si:H and poly-Si thin-film transistors (TFTs) fabricated by XeCl excimer laser annealing of a-Si:H films are discussed. The field-effect mobility of poly-Si TFT is 102 cm/sup 2//V-s, and that of a-Si:H TFT is 0.23 cm/sup 2//V-s. Their drain current on/off ratios are over 10/sup 6/. Except for the crystallization, the fabrication process was the same for both of them. This process appears extremely promising for the integration of matrix elements and peripheral drivers in a single substrate. >

Semiconductor laser module

Abstract: A semiconductor laser module comprises a semiconductor laser device, an optical fiber, and a lens for coupling light emitted from the semiconductor laser device to the optical fiber There is provided a metal base having a flat portion and a pipe portion in a metal case The semiconductor laser device is mounted on a chip carrier which is mounted on the flat portion of the metal base The lens is fixed in the inside of the pipe portion of the metal base The optical fiber is protected at one end by a ferrule which is fixed to the pipe portion of the metal base A device such as a monitor photodiode and a thermistor may be mounted on the flat portion of the metal base The flat portion of the metal base may be formed with a concave portion of an area smaller than an area of the bottom of the chip carrier The chip carrier is soldered to the flat portion of the metal base by a low temperature solder to provide thermal connection therebetween, and by a spot welding at a point other than the soldered portion of the low temperature solder

Key distribution system based on identification information

Abstract: A key distribution system (KDS) based on identification information (ID-based KDS) is presented. The system is founded on the Diffie-Hellman public key distribution scheme and has an identity authentication function. It uses an individual user's identification information instead of the public file used in the Diffie-Hellman scheme. It does not require any services of a center to distribute work keys or users to keep directories of key-encrypting keys. Therefore, key management in cryptosystems can be simplified by adopting the ID-based KDS. Two kinds of identity-based key distribution system are proposed and applied to actual communication networks. One uses two-way (interactive) communication to distribute work keys, while the other uses one-way communication. Modular exponentiations of large numbers, used in the systems, are implemented with digital signal processors. >

Variation in T c and carrier concentration in Tl-based superconductors

Abstract: ${T}_{c}$ variations observed in some Tl-based superconductors were investigated. Clear correlations were found between ${T}_{c}$, carrier concentration, and c-axis length. In particular, for ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{CuO}}_{6}$, a decrease in oxygen content of about 0.1 per formula unit, which corresponded to a decrease in hole concentration of 0.2, increased ${T}_{c}$ up to about 80 K, and elongated the c axis by about 0.4%. The carrier concentration in that system could be decreased by substitution of La for Ba, which resulted in an increased ${T}_{c}$ value. ${T}_{c}$ variations caused by a change in oxygen content were also observed in ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$ and ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Ca}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{10}$. It was demonstrated that superconductivity appears in a certain appropriate range of carrier concentration.

Semiconductor device having multilayered wiring structure with a small parasitic capacitance

Abstract: The semiconductor device of the present invention includes a semiconductor substrate on which are formed semiconductor elements, and a plurality of wiring layers formed on the semiconductor substrate via porous insulating films. The surface of the plurality of the wiring layers is preferably covered with a compact insulating film. The size of the pores in the porous insulating film is preferably 5 nm to 50 nm in diameter, and the volume of the pores in the porous insulating film is preferably 50% to 80% of the total volume of the porous insulating film. The porous insulating film is formed by subjecting a mixed insulating film of a basic oxide and an acidic oxide to a heat treatment to precipitate only either one of the basic oxide and the acidic oxide, and then dissolving out selectively the basic or acidic oxide precipitated.

Speech analysis and synthesis system

Abstract: A speech analysis and synthesis system operates to determine a sound source signal for the entire interval of each speech unit which is to be used for speech synthesis, according to a spectrum parameter obtained from each speech unit based on cepstrum. The sound source signal and the spectrum parameter are stored for each speech unit. Speech is synthesized according to the spectrum parameter while controlling prosody of the sound source signal. The spectrum of the synthesized speech is compensated through filtering based on cepstrum.

Three dimensional ICs, having four stacked active device layers

Abstract: The four-layer-stacked master slice is proposed as a system application for 3-D ICs. The master slice consists of a programmable logic array for logic circuits, a CMOS gate array for I/O interface buffer circuits, and a CMOS SRAM. Fabrication technologies for the four-layer-stacked 3-D IC are described. Laser beam recrystallization was carried out for the formation of three SOI (silicon-on-insulator) layers in the 3-D IC. Recrystallization without cracks in both SOI and vertical isolation layers was accomplished by adjusting laser annealing conditions. Microprobe Raman spectroscopy data indicated that a tensile stress of (3-6)*10/sup 9/ dyne/cm/sup 2/ was present in each SOI layer. Surface planarization of the vertical isolation layer was carried out with a combination of polystyrene spin coating and dry etching. An initial surface roughness of about 1.7 mu m was successfully reduced to less than 500 A, and the planarized surface did not interfere with either recrystallization or photolithography. NMOSFETs and PMOSFETs, fabricated in the four-layer-stacked 3-D IC, have been successfully operated. >

Output‐buffer switch architecture for asynchronous transfer mode

Abstract: This paper proposes a new asynchronous transfer mode (ATM) switch architecture for the broadband ISDN. The ATOM switch ATM output-buffer modular switch has a multi-stage network structure, and is highly modular to facilitate capacity expansion. The ATOM switch element is of the output-buffer type with a time-division multiplexed bus and FIFO buffer for each outgoing line. Bit-slice techniques are used to implement the high-speed time-division bus and buffer memories. The output buffer switch has the advantages of no throughput degradation since internal contention is eliminated, and a simple control structure for providing priority and multi-point connections. This paper also deals with switching delay and buffer overflow probabilities for mixed (bursty and non-bursty) traffic.

High critical currents in epitaxial YBa2Cu3O7−x thin films on silicon with buffer layers

Abstract: As‐deposited superconducting thin films (∼0.1 μm) of YBa2Cu3O7−x have been prepared by pulsed laser deposition on (100) Si with buffer layers of BaTiO3/MgAl2O4. X‐ray diffraction studies reveal that the films grow epitaxially with the c axis preferentially oriented normal to the substrate surface. This is confirmed by ion channeling measurements along the (100) (normal to the surface) and (110) directions of the Si substrate showing a minimum yield of 54% along the (100), and 78% along the (110) axes using 2.8 MeV He++. Preliminary transmission electron microscopy study also supports these results. The as‐deposited films have zero resistance temperatures of 86–87 K, and critical current densities of 6×104 A/cm2 at 77 K and 1.2×105 A/cm2 at 73 K. Our results indicate that the superconducting properties of the films are limited primarily by the quality and degree of epitaxal growth of the buffer layers on the silicon substrate.

A resource sharing and control synthesis method for conditional branches

Abstract: A scheduling/allocation and control synthesis algorithm is presented. The proposed algorithm can achieve good resource sharing and synthesize an efficient control sequence for nested conditional branches as well as for straight-line codes. The condition vector concept is introduced to allow mutual exclusion to be detected among operators, and is used to produce more efficient control sequences. The condition vector concept is concerned with the handling of nested condition branches and can be used for other scheduling methods. Results obtained from several experiments indicate that the proposed algorithms are efficient and effective. >

A silicon electrostatic ultrasonic transducer

Abstract: An electric ultrasonic transducer is developed by using a silicon IC process. Design considerations are first presented to obtain high sensitivity and the desired frequency responses in air. The measured transmitter sensitivity is 19.1 dB (0 dB=1 mu bar/V) at a point 50 cm away from the devices, when the devices are operated at 150 kHz. The receiving sensitivity is 0.47 mV/Pa in the 10-130-kHz range, with bias voltages as low as 30 V. An electronic sector scanning operation is also achieved by time-sequentially driving seven elements arranged in a linear array on the same chip. The results should be helpful in the design of phased-array transducers integrated with electronic scanning circuits. >

Packet-switched communications network with parallel virtual circuits for re-routing message packets

Abstract: In a packet-switched communications network, each of a plurality of terminals sequentially transmits control packets in response to a request for call before sequentially transmitting message packets. A switching node of the network is responsive to the control packets for establishing first and second logical channels through the network. Message packets are propagated through the first logical channel. The established logical channels are monitored to detect an abnormal condition. In the event of an abnormal condition in the first logical channel the message packets are re-routed to the second logical channel.

Electrically erasable and programmable non-volatile memory (EEPROM), wherein write pulses can be interrupted by subsequently received read requests

Abstract: A microcomputer having an electrically erasable and programmable nonvolatile memory into which data is written without prolonging the data write processing time, even when a data read request is issued during the data write processing operation. The microcomputer includes a data erasing/writing/reading control circuit which coordinates the writing and reading of data to and from memory. The control circuit includes a timer for counting a predetermined number of counts during the data write process corresponding to the time period required to positively write data into the memory. If a data read request occurs during the data write process, the counting of the timer is suspended while the data is read out from the memory. After the data read process is completed, the data write process is resumed, and the timer continues counting toward the predetermined count from the count at which it was suspended. When the timer reaches the predetermined count, the data has been positively written into memory, and the data write process is terminated.

Variation in Tc, structure and oxygen content in Tl2Ba2CuO6 and their correlations

Abstract: The preparation condition of Tl 2 Ba 2 CuO 6 (2201 compound) and its properties including superconductivities and structural variations were studied. Preparation at relatively low heat-treatment temperatures produced the 2201 compound with an orthorhombic symmetry, while heat-treatment above 840°C produced a tetragonal symmetry. It was revealed that the appearance of superconductivity was independent of the structural symmetry, and was strongly affected by oxygen content. Decrease of oxygen content by quenching or Ar-annealing increased the superconducting transition temperatures up to about 70 K. A positive correlation between T c and the c -axis length was also found for all samples including both orthorhombic and tetragonal structures.

Output-buffer switch architecture for asynchronous transfer mode

Abstract: An asynchronous transfer mode (ATM) switch architecture for the broadband integrated services digital network (ISDN) is proposed. The proposed switch, called ATOM switch (ATM output-buffer modular switch), has a multistage network structure, retaining a high degree of modularity for capacity expansion. The ATOM switch element belongs to an output-buffer switch category, and it has a time-division-multiplexed bus and first in, first out buffers for individual outgoing lines. A bit-sliced circuit structure is adopted to implement the high-speed time-division bus and buffer memories. The proposed switch has no throughput degradation because of internal blocking, and has a simple control structure for providing a priority scheme and multicast connections. >

Semiconductor device and method of manufacturing the same

Abstract: PROBLEM TO BE SOLVED: To provide a semiconductor device which can take a sufficient number of bumps with a low cost and a small size, and also to provide a method for manufacturing the device. SOLUTION: The semiconductor device includes a semiconductor element 1 having a plurality of electrodes 1a, a resin film 3 joined on its one surface to the element 1 and formed therein with through-holes 4 at positions corresponding to the plurality of electrodes 1a, a plurality of conductors 5 formed as extended from the other surface of the film 3 onto the through-holes 4 of the film 3, a plurality of bump electrodes 6 for joining the electrodes 1a of the element 1 and the conductors 5 on the film 3 via the through-holes 4, and a plurality of bumps 7 formed on the respective conductors 5 formed on the film 3.

Flat cooling structure of integrated circuit

Abstract: A circuit assembly with circulation of coolant. A plurality of chips of integrated circuit are arranged on a substrate separately from each other in rows and columns. A circulating unit disposed on the substrate and having a planar shape circulates coolant therethrough. The circulating unit has within its bottom side a plurality of cells arranged in rows and columns correspondingly to the plurality of chips. Each individual cell is thermally connected to the corresponding individual chip so as to receive therefrom heat generated thereby. The circulating unit includes a distributor for distributing to the respective cells the circulated coolant effective to absorb the heat received in the respective cells.

Speaker-independent word recognition using dynamic programming neural networks

Abstract: A description is given of speaker-independent word recognition based on a new neural network model called the dynamic programming neural network (DNN), which can treat time-sequence patterns. DNN is based on the integration of a multilayer neural network and dynamic-programming-based matching. Speaker-independent isolated Japanese digit recognition experiments were carried out using data uttered by 107 speakers (50 speakers for training and 57 speakers for testing). The recognition accuracy was 99.3%, suggesting that the model can be effective for speech recognition. >

Data communication system having a speed setting variable with transmission quality factors

Abstract: In a full-duplex data communication system, the signal-to-noise ratio, error rate and occurrences of out-of-sync condition of signals transmitted on the data channel of a first transmission medium from a first station to a second station are detected by the latter and a first set of quality signals of the first transmission medium is generated. The signal-to-noise ratio, error rate and occurrences of out-of-sync condition of signals transmitted on the data channel of a second transmission medium in the opposite direction are likewise detected by the first station and a second set of quality signals of the second transmission medium are generated. The first set of quality signals are modulated and transmitted on a control channel of the second transmission medium from the second station and received and demodulated by the first station, which derives a speed setting command signal from the second set of quality signals as well as from the first set of quality signals represented by the demodulated signals, and the transmission speed of the first station is controlled according to the speed setting command signal. The speed setting command signal is modulated and transmitted on a control channel of the first transmission medium from the first to second station, which demodulates it and controls its transmission speed according to the demodulated speed setting command signal.

Flip chip type semiconductor device

Abstract: A flip chip type semiconductor device includes a substrate, a polyimide film and an inorganic passivation film. An opening having a rectangular configuration is formed in the inorganic passivation layer provided on an electrode pad. The polyimide film is formed within the opening and on the inorganic passivation layer only in the vicinity of the opening so that the polyimide film is not formed on a circuit element of the semiconductor device. A circular window is formed in the polyimide film within the opening. A bump structure formed in the window is electrically connected to the electrode pad.

Preamable detection circuit for digital communications system

Abstract: In a burst mode digital communication system, a preamble containing a predetermined bit pattern and a digital signal are modulated upon orthogonal carriers and transmitted in a series of burst signals. At a distant end of the system, the preamble and the digital signal are noncoherently detected with locally generated orthogonal carriers having the same frequency as the transmitted orthogonal carries to produce in-phase and quadrature signals. First and second correlators are provided to perform a correlation calculation between a locally generated bit pattern and the in-phase signal and to perform a correlation calculation between the local bit pattern and the quadrature signal. A phase error of the local carriers with respect to the transmitted carriers is detected from the outputs of the first and second correlators. A clock phase error of a locally generated clock pulse with respect to symbols contained in the transmitted burst signals is detected from one of the outputs of the correlators. Power level detector is connected to the outputs of the correlators for detecting a power level of the received burst signals. The carrier and clock phase error detection as well as the power level detection are performed in a parallel fashion, allowing a reduction of the amount of information contained in the preamble.

High throughput communication method and system for a digital mobile station when crossing a zone boundary during a session

Abstract: In a digital radio communications system, a mobile station in the service zone of a first base station transmits a reconnect request packet to a second base station when leaving the service zone of the first and entering the service zone of the second during a session with the first base station. The second base station communicates the receipt of the reconnect request packet to the central station, from which a proceed-to-clear command packet is sent to the first base station to allow it clear the connection with the mobile station and return a clear response packet to the central station informing it of a serial number of the last data packet it has received from the mobile station immediately before leaving its service zone. On receiving the clear response packet, the central station sends a reconnect command packet indicating that serial number to the second base station to cause it to issue a reconnect response packet to the mobile station requesting the reconnect. The reconnect response packet communicates the serial number of the last packet to the mobile station to allow it to send a copy of data packets which may have been interrupted during the session with the first base station.

Birefringence diffraction grating type polarizer

Abstract: In a birefringence diffraction grating type polarizer, periodical proton ion-exchanged regions are provided on the principal plane of an optically anisotropic crystal substrate to provide an optical diffraction grating, and a dielectric layer is provided on each of the periodical proton ion-exchanged regions. The refractive index of the dielectric layer is proximate or equal to that of the crystal substrate, and the whole surface of the optical diffraction grating is covered by an anti-reflection layer of a single material having a uniform thickness.

Vertical power mosfet having high withstand voltage and high switching speed

Abstract: In a vertical field effect transistor including a source electrode and a gate on the front surface of a semiconductor substrate having one conductivity type and a drain electrode on the back surface of the substrate, the semiconductor device of the present invention has the structure wherein a connection region of one conductivity type positioned between two channel forming base regions of the opposite conductivity type is formed by a semi­conductor layer having a higher impurity concentration than the drain region of the one conductivity type, and the surface portion of the connection region which is connected to the channel has a lower impurity concentration than the connection region.

Packet switch suitable for integrated circuit implementation

Abstract: A packet switch for high-speed synchronous multiplexing of voice and picture communications collectively. The packet switch uses among other things an input multiplexer, and output demultiplexer, and a single buffer memory divided into memory areas connected to multiple input and output lines. The subdivided buffer is controlled by counters rather than a more complicated address exchanger. A second embodiment eliminates the need for an output demultiplexer because of individual read/write control of the buffer units. A third embodiment includes a bidirectional bus between an input buffer and an output buffer. A fourth embodiment uses a more economical unidirectional bus. The unidirectional bus can be limited to a part of an input packet to permit Large Scale Integration (LSI). In the LSI configuration, address filters may be replaced with a centralized address controller, and the buffer can consist of FiFo memory units or RAM units.

Mutations in a protein kinase C homolog confer phorbol ester resistance on Caenorhabditis elegans

Abstract: The tpa-1 gene mediates the action of tumor-promoting phorbol esters in the nematode Caenorhabditis elegans. A genomic fragment that constitutes a portion of the tpa-1 gene was cloned by Tc1 transposon tagging and was used as a probe to screen a nematode complementary DNA library. One of the isolated complementary DNA clones had a nucleotide sequence that predicts a polypeptide of 526 amino acids. The predicted amino acid sequence revealed that the predicted tpa-1 protein sequence is highly similar to protein kinase C molecules from various animals, including man.

Mobile telephone station with power saving circuit

Abstract: A mobile station comprises a receiver for receiving a signal from the base station and a transmitter including a frequency synthesizer, a modulator and a power amplifier connected to it For power savings purposes, the transmitter is deactivated during a standby mode If an earlier portion of a signal received from the base station indicates a likelihood of a need to return an acknowledgment, power is supplied to the frequency synthesizer to allow it to stabilize in advance If a later portion of the received signal indicates that there actually exists the need to acknowledge the receipt of the signal, the power amplifier is subsequently activated and an acknowledgment signal is returned through it to the base station If the later portion of the received signal indeicates the absence of the need to acknowledge, the frequency synthesizer is again deactivated and the power amplifier remains deactivated