Showing papers by "NEC published in 1980"

External optical feedback effects on semiconductor injection laser properties

Abstract: Influences on the semiconductor laser properties of external optical feedback, i.e., return of a portion of the laser output from a reflector external to the laser cavity, have been examined. Experimental observations with a single mode laser is presented with analysis based on a compound cavity laser model, which has been found to explain essential features of the experimental results. In particular, it has been demonstrated that a laser with external feedback can be multistable and show hysteresis phenomena, analogous to those of non-linear Fabry-Perot resonator. It has also been shown that the dynamic properties of injection lasers are significantly affected by external feedback, depending on interference conditions between returned light and the field inside the laser diode.

An Analysis of Automatic Equalizers for Orthogonally Multiplexed QAM Systems

Abstract: A simple structure of a per-channel automatic equalizer for an orthogonally multiplexed QAM system is proposed and the performance is analyzed. It is shown that a dual automatic equalizer with T/2 -long tapped delay lines, where T is a period of individual baseband baud, can equalize not only the transmission channel distortions, but the timing deviations and demodulating carrier phase deviations. Despite its high efficiency, the orthogonally multiplexed QAM system has been regarded as overly costly. However, by using the dual automatic equalizer with fairly simple structure, the system is competitive with conventional single channel data transmission systems.

Microoptic grating multiplexers and optical isolators for fiber-optic communications

Abstract: As new optical devices for increasing further the utility of and to expand the application of fiber-optic communications, grating multiplexers and isolators have been developed for 0.8 μm band employing microoptic approach. The development of these devices is the subject of this paper. The devices have desirable features of small size, compactness, high optical performances, and high reliability. The grating multiplexer consists of a graded-index rod, a blazed reflection grating replicated onto the graded-index rod slanting facet or a wedge facet, and an input-output fiber array. Simple calculations have been done to determine necessary element parameters for a given channel spacing. Experimental results are presented for five-channel multiplexers devised using a SELFOC®lens. Around 3 dB insertion loss and less than -30 dB crosstalk have been obtained for about 35 nm channel spacing in overall device size of 18 \times 13 \times 50 mm. Faraday rotation optical isolators for 0.8 μm band have been miniaturized by employing an efficient paramagnetic glass Faraday rotator, a magnet with a through hole and a folded optics in the Faraday rotator. The path number in the folded optics has been optimized in terms of trading-off between the magnet size and the insertion loss. A 0.9 dB insertion loss including fiber coupling loss and 36 dB isolation have been obtained in overall device size of 24 \times 24.5 \times 42 mm. Results on the temperature and wavelength dependence of the isolation are also presented. In addition, fundamental properties of optical circulators for 0.8 μm band and optical isolators and circulators both for 1.3 μm band, developed as extended modifications of the optical isolators for 0.8 μm band, are briefly described.

Superconductivity in graphite-alkali metal intercalation compounds

Abstract: Superconducting properties of pseudo-single crystals of C8K were mainly investigated by the low frequency AC magnetic susceptibility and the electrical resistivity. The measured values of Tc dispersed from 128 mK to 198 mK for 13 samples. The measurements of the superconducting transition under magnetic field revealed a remarkable anisotropy due to the field angle θ measured from the layer plane, i.e., a type I superconductivity was observed for 25°⪅¦θ¦≦ 90dg and a type II for 0°≦¦θ¦⪅25°. The angular dependences of Hc2 and Hc3 were fairly well explained by the effective mass model. The Hc2 versus T curve under magnetic field perpendicular to the c-axis showed a positive curvature in the temperature range near Tc.

An Electron Diffraction Study on Mixed PdCl2 / SnCl2 Catalysts for Electroless Plating

Abstract: The activated or catalyzed surface conditions for initiating electroless metal deposition were studied by means of transmission electron microscopy and electron diffraction analysis Four mixed catalysts, including two commercial samples, and five accelerators (, , , , and ) were used in this study The acceleration with gave the finest remaining particles which were almost bare active nuclei, while the acceleration with ammonate group ( and ) coagulated small particles to produce high density particles The electron diffraction patterns after activation, for the catalysts prepared in our laboratory, showed amorphous broad diffraction rings which were explained as fcc structure, while for the commercial catalysts, they showed relatively sharp and netlike profiles which could be attributed to orthorhombic structure The electron diffraction patterns after acceleration with became the sharper profiles of fcc structure, however in the case of ammonate group, they showed the complicated profiles of non‐fcc structure Finally the catalytically active sites or nuclei are discussed

Log-Weibull distributed sea clutter

Abstract: Sea clutter was measured using and L-band long-range air-route surveillance radar (a.r.s.r.) at very low grazing angles between 0.13° and 0.25°. From the stored data of six scans, it is shown that the sea-clutter amplitude statistics obey a log-Weibull distribution.

Super low-noise GaAs MESFET's with a deep-recess structure

Abstract: Super low-noise GaAs MESFET's for replacement of parametric amplifiers have been successfully developed by adopting a deep-recess structure. The structure of a 0.5-µm gate in a deeply recessed region with a cylindrical edge shape has enabled reduction of the source resistance to a half of that of conventional flat-type MESFET's. The noise figure was improved by more than 0.5 dB by this reduction of the source resistance, and less than 2.0-dB noise figure has been reproducibly obtained at 12 GHz. The best noise figures were 0.7 dB (14.9-dB gain) at 4 GHz and 1.68 dB (10.7-dB gain) at 12 GHz. The developed MESFET's were applied to two-stage amplifiers of 11.7-12.2-GHz band, and the noise figure obtained was 2.16 dB ( T_{e}: 185 K) at room temperature and 1.94 dB ( T_{e}: 163 K) at 0°C. This performance is good enough to replace some of parametic amplifiers.

An advanced PSA technology for high-speed bipolar LSI

Abstract: An advanced method for polysilicon self-aligned (PSA) bipolar LSI technology has realized a miniaturized transistor for high performance. By introducing the overlapping structure for double polysilicon electrodes, the emitter area is reduced to 1 µm × 3 µm and the base junction is reduced to 0.3 µm. The CML integrated circuit composed of this transistor has achieved a minimum propagation delay time of 0.29 ns/gate with power dissipation of 1.48 mW/gate. Compared to the conventional PSA method, this technology promises to fabricate higher speed and higher density LSI's.

A high-power GaAs MESFET with an experimentally optimized pattern

Abstract: A high-power GaAs MESFET with a high packing density has been developed in order to increase the total gatewidth within limited practical device size. The gate-finger width was experimentally optimized to increase the packing density without deterioration of the power gain. The developed power MESFET is the crossover structure and has a total gatewidth of 15 mm with gate-finger width of 190 µm in a 2.2-mm-wide chip. The packing density was almost doubled, and the output powers of 25 W at 6 GHz, and 17 W at 8 GHz were obtained from the internally matched four-chip devices.

Asynchronous circuit responsive to changes in logic level

Abstract: An integrated circuit operable with low power consumption and high reliability is disclosed. The circuit comprises a logic circuit receiving an input logic signal at its input, detection means for detecting a change in the logic input signal, means responsive to an output of detection means for producing a control signal, and control means responsive to the control signal for setting the logic circuit at a predetermined condition irrespective of the input logic signal.

Adaptive predictive coding for newspaper facsimile

Abstract: An adaptive predictive coding method, which efficiently encodes newspaper pages with printed text and screened photographs is presented. This coding technique utilizes two kinds of predictors with different reference picture elements (pels). One is applied to printed text and the other is applied to screened photographs. The Dth previous pel and its neighboring pels age adopted as the reference pels for the photograph predictor, where distance D coincides with the screen period. Comparing the adaptive predictive coding with a typical document facsimile coding, the data compression ratio is improved by about two times for a screened photograph (compression ratio is 5 ∼ 6) and is almost the same or slightly higher for printed text. Computer simulation shows that if a 500-kbits buffer memory is employed, it is possible to transmit most pages, including an extreme case of a 100 percent photograph page, with a 4500-rev/min scanner at a transmission bit rate of 128 kbit/s. For average pages the revolution speed can be raised to 6000 rev/min. Page transmission time of about 5 min in analog facsimile through a 48-kHz band can be reduced to 1.8 min by adopting the digital transmission with a 128-kbit/s data modem and the adaptive predictive coding technique, when the facsimile revolution speed is set at 6000 rev/min.

Holographic disk with high data transfer rate: its application to an audio response memory

Abstract: This paper describes a memory realized with a high data transfer rate using the holographic parallel-processing function and its application to an audio response system that supplies many audio messages to many terminals simultaneously. Digitalized audio messages are recorded as tiny 1-D Fourier transform holograms on a holographic disk. A hologram recorder and a hologram reader were constructed to test and demonstrate the holographic audio response memory feasibility. Experimental results indicate the potentiality of an audio response system with a 2000-word vocabulary and 250-Mbit/sec bit transfer rate.

Analysis of short-channel MOSFET's with field-dependent carrier-drift mobility

Abstract: MOSFET I_{D}-V_{D} characteristics have been investigated, using two-dimensional analysis which includes field-dependent carrier-drift mobility. It is predicted that drain current is affected by the relationship between carrier-drift velocity and electric-field strength. Reduction mechanisms for normalized drain current and current saturation voltage for short-channel MOSFET's have become clear. In the light of the above analysis, an analytical model is presented. The model is simple, in spite of taking the field-dependent carrier-drift mobility and the proper current saturation concept into account. Predicted results are in good agreement with experimental data down to L = 1 µm.

Integrated memory circuit

Abstract: The integrated circuit is operable with low power consumption and high reliability. This circuit comprises a logic circuit (11) receiving an input logic signal (Ao-An) at its input, detection means (17) for detecting a change in the logic input signal, means responsive to an output of detection means for producing a control signal (CE), and control means responsive to the control signal for setting the logic circuit at a predetermined condition irrespective of the input logic signal.

Electro-optic light deflector

Abstract: An electro-optic material has at least a pair of confronting elongated electrodes formed on at least one surface thereof. Preferably, each of the electrodes has a plurality of elongated, spaced parallel fingers which interleave with each other (sometimes called "interdigital electrodes"). When a high-frequency signal is applied across the electrodes, the refractive index changes in a linear or nonlinear manner within a layer of the body of the electro-optic material which is near the electrodes. The amount of the index change may be varied by a proper selection of materials, signals and geometrical material configuration.

Invertible multiple-pass ribbon cartridge having two capstans

Abstract: A ribbon cartridge for a serial printer includes a casing containing a supply reel, a take-up reel and a ribbon drive roller. A lower axial end of the drive roller is slotted to receive a drive shaft of a ribbon advance motor on the serial printer. The upper axial end of the drive roller is connected by a tension band to the upper end of the take-up reel shaft. The cartridge may be inverted by removing the tension band from the shafts of the drive roller and take-up reel, inverting the cartridge, and replacing the tension band on the shaft of the other reel and the shaft of a drive roller associated with the second reel.

Non-rayleigh weather clutter

Abstract: Radar echoes were observed from rain clouds in a range interval of 60 to 65.6 n mile, over an azimuth interval of 41.8° to 54.2° (range sweep number 400?519), above the sea. The variation in the distribution of clouds was examined over a 50s period. It is then shown that weather clutter obeys a Weibull distribution.

Word line selection in a semi-conductor memory device

Abstract: A memory device operable at high speed is disclosed. The device comprises selection means (WD) coupled to word lines (WL) for selecting one of them, detection means (WDT) for detecting a signal appearing in the selected word line, and word line drive means (WDR) responsive to an output of the detection means for supplying the selected word line with a voltage capable of introducing a selection level in it independent on the selection means.

A Simple Firmware Realization of PCM Framing Systems

Abstract: A new alternative to PCM framing system implementation is presented, which exploits LSI memories for performance improvement and hardware simplification. The proposed system simply consists of a tapped delay line for simultaneous observation of multiple framing bits and an ROM programmed sequence controller for framing system operation. Application to D3 format PCM signals is described in detail. Performance analyses, made by using signal flow graphs, show that the approach presented here is a superior alternative to the conventional approach.

Cooling system for a line printer

Abstract: A line printer has a flexible character band (5) which carries type characters which are struck by individually actuatable hammers (19). A plurality of hammer actuators (8) for individually actuating the hammers (19) are cooled by air directed upon them from above by air moving means (9).

1-µm MOS process using anisotropic dry etching

Abstract: Anisotropic and selective etching of silicon has been obtained using a planar-reactive sputter-etching system and CCl 3 F gas. The Si to SiO 2 etch-rate ratio was 5 : 1. This etch process in CCl 3 F was interpreted as mainly involving physical reaction as opposed to etching in SF 6 . The influence of reactive sputter etching on junction leakage and threshold voltage shift, in comparison with a conventional wetetch process, could not be observed in the electrical characteristics of polysilicon gate MOS devices. An all dry-etched MOS process, consisting of an anisotropic etching for Si 3 N 4 , polysilicon, SiO 2 , and aluminum, was applied to the fabrication of a 1-kbit static RAM with 1-µm minimum geometry. It was confirmed that this anisotropic etching technology was useful for very fine-geometry patterning and could be applied to a 1-µm MOSLSI manufacturing process.

A New-Type of Electronic Circulator at 800MHz Band

Abstract: A new way to construct an electronic circulator by using transistors is proposed, and the characteristics of such an active circulator at 800MHz are presented. This is suitable for a monolithic integrated circuit, because no magnetic is used.

Method of manufacturing ceramic capacitors

Abstract: A ceramic capacitor is prepared by corting an electrode paste on the opposite surfaces of a green ceramic body. The electrode paste contains an inorganic binder having the same composition as the green ceramic body. Then the green ceramic body is sintered and at the same time the electrode paste is baked to form electrodes for attaching lead wires.

Electrooptic light deflector

Abstract: An electrooptic light deflector controls the deflection of a light beam in response to an applied electrical signal based on the electrooptic effect. In order to provide a comparatively large deflection angle (θ) without the necessity of a high-voltage generating circuit the deflector of the present invention comprises a plate (1) of a light transmissive material, electrodes (2) formed on the surface of the plate (1), and a voltage source (3) for generating a voltage, means for supplying the voltage to the plate (1) to change the distribution of the refractive index in its thickness direction so that a light beam (4) incident upon one end surface of the plate (1) is deflected in response to the change in the distribution of the refractive index formed in the plate (1).

Hot cathode discharge lamp lighting device

Abstract: A parallel circuit of a capacitor and a switching element is connected to a hot cathode discharge lamp lighting device using a high frequency and high voltage generating means for permitting the flow of current into the filaments of the hot cathode type discharge lamp only at the lamp starting time. The switching element of the parallel circuit is a current controlled resistance element, such as a switching semiconductor, having a break-over voltage V BO lower than the capacitor terminal voltage during the initial ignition period and higher than the capacitor terminal voltage during the reignition or operation period, whereby the filament current to the discharge lamp may be used for preheating of the filament in the initial ignition period. The filament current may be stopped or reduced by turning off of the switching element by raising the terminal voltage of the capacitor in the reignition period during normal operation. Thus, the lumen-per-watt efficacy of the lighting device is improved since the filament current is substantially eliminated during the lamp operation. After the initial ignition period it is preferred to use the capacitor of the parallel circuit as an intermittent commutation capacitor in the high frequency and high voltage generating oscillation circuit having an oscillation capacitor, a nonlinear inductor and a thyristor.