Showing papers by "NEC published in 1982"

Injection locking properties of a semiconductor laser

Abstract: Injection locking properties of a semiconductor laser have been analyzed, taking into account the injected carrier density dependent refractive index in the active region. It has been found that this dependence significantly affects the injection locking properties, giving rise to a peculiar asymmetric tuning curve and dynamic instability. The instability originates from the intermode interaction via the modulation in the injected carrier density caused by intensity beat. The detuning dependence of the direct modulation response characteristics inside and outside of the locking range have also been examined.

Effects of impurity doping in lead zirconate-titanate ceramics

Abstract: Impurity doping effects on the properties of lead zirconate-titanate ceramics have been investigated from the internal bias field viewpoint. The internal bias field is strengthened by doping with single or multiple acceptors, but is weakened by single or multiple donors. Equimolar mixed acceptor and donor dopants have no influence on the internal bias field. These facts suggest that the internal bias field is caused by complexes of acceptor atoms and oxygen vacancies. The internal bias field gives rise to effects on the domain wall motions. It prohibits the poling process, increases the mechanical quality factor and accelerates the aging change in the frequency constant. The mechanical quality factor and the aging change are proportional to the internal bias field. However, when the internal bias field reorients itself parallel to the spontaneous polarization in a short time after poling, the aging change becomes small, even for a specimen having a strong internal bias field.

1/f noise in n-channel silicon-gate MOS transistors

Abstract: It is found that equivalent gate noise power for l/f noise in n-channel silicon-gate MOS transistors at near zero drain voltage at room temperature is empirically described by two noise terms, which vary as K_{1}(q/C_{ox}) (V_{G} -V_{T})/f and K_{2}(q/C_{ox})^{2}/f, where V_{G} is gate voltage, V T is threshold Voltage, and C ox is gate-oxide capacitance per unit area. Unification of carrier-density fluctuation (McWhorter's model)and mobility fluctuation (Hooge's model) can account for the experimental data. The comparison between the theory and experiment shows that the carrier fluctuation term K 2 is proportional to oxide-trap density at Fermi-level. The mobility fluctuation term K 1 is correlated to K 2 , being proportional to \radic K_{2} . The origin of this correlation is yet to be clarified.

Interline CCD image sensor with an anti blooming structure

Abstract: THE APPLICATION OF AN overflow drain and barrier positioned beside the photosensitive area? has made it possible to suppress blooming of CCD image sensors. However, this method was found to sacrifice photosensitivity and dynamic range. This paper will describe an interline CCD sensor where the vertical overflow drain is positioned under, rather than beside the photodiode. Thus the cell area can now be used effectively for photoelectron generation and storage, and increased photosensitivity and dynamic range can be maintained. Furthermore, this technique eliminates the blooming phenomenon.

Quadruply self-aligned stacked high-capacitance RAM using Ta 2 O 5 high-density VLSI dynamic memory

Abstract: A new one-transistor, one-capacitor RAM cell structure called a Quadruply Self-Aligned Stacked High Capacitance (QSA SHC) RAM is proposed as a basic cell for a future one-million-bit VLSI memory. This cell consists of a QSA MOSFET and a Ta 2 O 5 capacitor stacked on it. By this cell, the ultimate cell area 3F \times 2F can be realized with sufficient operating margin. Here, F is the minimum feature size. The basic cell was fabricated and its operation was experimentally verified. The leakage current of Ta 2 O 5 film was small enough for the storage capacitor dielectric. Using a 3F \times 4F cell and a 4F pitch sense amplifier, a one-million-bit memory was designed with a 2-µm rule. A cell size of 6.5 × 8 µm2, and a chip size of 9.2 × 9.5 mm2were obtained. The access time, neglecting the RC time constant of the word line, was estimated to be about 170 ns. Based on this design, it is argued that a future one-million-bit memory can be realized by QSA SHC technology with a 2-1-µm process. The mask set of the 1-Mbit RAM was actually fabricated by an electron-beam mask maker. A photomicrograph of the 1-Mbit RAM chip patterned by the mask set is shown. This chip was patterned not to get an operating sample but to show an actual chip image of the future 1- Mbit RAM. The area of each circuit block including storage array can be seen in this chip image.

Lever actuator comprising a longitudinal-effect electroexpansive transducer and designed to prevent actuation from degrading the actuator

Abstract: A transducer (51) extended by an electroexpansive longitudinal effect, actuates a lever (77) through a bendable plate (56). Preferably, the plate actuates a first arm (53) having an end which provides the fulcrum. Another bendable plate (79) actuates a second arm (76) having an end which exterts the power to the lever. The plates are symmetrically disposed on both sides of the transducer axis. The lever is differentially actuated by the arms. When such lever actuators are combined into an impact printer head, a guide for printing elements carried by the respective levers are preferably used in preventing the levers from excessively excursing.

Integrated optical switch matrix for single-mode fiber networks

Abstract: Design analysis and experiments on optical directional coupler switch integration into an LiNbO 3 chip with arrayed fiber pigtails has been made at 1.3 μm wavelength. A limitation for high integration was discussed by taking into account radiation losses at connecting waveguides between switch elements and at the input/output curved waveguide, switching voltage, and crosstalk caused by applied electric field leakage. An optimum designed low-loss 4 × 4 switch matrix with arrayed fiber pigtails at 1.3 μm wavelength has been developed. Its insertion loss was measured to be as low as 6 dB.

Perfect duality for convexlike programs

Abstract: The minimizing problem for a convex program has a dual problem, that is, the maximizing problem of the Lagrangian. Although these problems have a duality gap in general, the duality gap can be eliminated by relaxing the constraint of the minimizing problem, so that the constraint is enforced only in the limit. We extend this result to the convexlike case. Moreover, we obtain a necessary condition for optimality for minimizing problems whose objective function and constraint mapping have convex Gateaux derivative.

Production process and high density recording characteristics of plated disks

Abstract: A high density recording plated disk, which consists of a chemically plated Co-Ni-P medium and a spin-coated and lubricated SiO 2 overcoat, has been developed using techniques based on extensive studies on error defects, wear durability and wet durability throughout all the production processes. The plated disks were evaluated by practical level tests. The average numbers of error defects were about 50 per surface at 620FRPM (15,700FRPI) linear density measured with 18.5 μm track width Mn-Zn ferrite heads. The plated disk wear durability was sufficient for 20,000 contact start/stop (CSS) cycle tests and 108times seek motion test at 0.2 μm flying height with Mn-Zn ferrite heads. Wet durability was determined for humidity tests under 40 °C, 80% R. H. for 7 months. Errors were not increased after the tests. Based on these excellent evaluation results, the plated disks are used in an 8 inch high performance 400 MB disk drive developed by NTT. Further, higher density recording characteristics of the plated disk were investigated using narrower gap length Mn-Zn ferrite heads at smaller head-medium spacings. As a result, 2,900 FRPM (74K FRPI) linear recording density was obtained as D 50 with a 0.03 μm thick Co-Ni-P medium disk and a 0.2 μm gap length head at 0.12 μm head-medium spacing.

Continuous speech recognition system

Abstract: A continuous speech recognition system determines the similarity between input patterns and reference patterns over time such that similarities between previously spoken speech patterns and reference patterns are determined while speech continues to be spoken. Degrees of dissimilarity at arbitrary reference pattern word times are determined asymptotically and are recorded. The minimum degree of dissimilarity is determined and the corresponding word is categorized. Recognition decisions are ultimately made in reverse chronological order.

Integrated tapped MOS analogue delay line using switched capacitor technique

Abstract: A tapped MOS analogue delay line based on the switched capacitor technique for realisation of low-power analogue LSIs is fabricated using a VLSI process. Excellent characteristics such as large signal handling capability, low total harmonic distortion of −85 dB for 3V(p-p) input and fast operation speed of more than 1 MHz clock rate with negligible charge transfer loss are obtained.

Television bandwidth compression transmission by motion-compensated interframe coding

Abstract: ‘S UPPORTED by progress in satellite communications, digital signal processing technologies, and a strong need for advanced communications media, video communication will be introduced widely in business activities. Domestic satellite communication systems in North America grew in the last decade to more than one hundred satellite transponders in orbit. Satellite use for video communication began with broadcast television program transmission in the 4/6 GHz band in the early 1970’s. It expanded rapidly to television program distribution for CATV and pay TV services in the late 1970’s. Cost reduction of the television receive-only earth station has brought about one-way video teleconferencing in the business area. Two-way teleconferencing has a long development history. The increasing burden of business travel has heightened the need for a substitute. The development of 12/14 GHz satellite communications systems permitted small antenna earth stations, enabling direct access to digital networks from user’s premises. This made it possible for a company to have its own wide-band network. Indeed, some big companies have started building their own satellite communications network(s) which can include two-way video teleconferencing systems (Fig. 1). American Telephone and Telegraph has just introduced a public video teleconferencing service network, Picturephone Meeting Service, which employs both satellite and terrestrial wideband transmissions systems. Bandwidth compression techniques, as well as digital transmission networks, were key to video signal transmission cost reduction, which in turn was essential to practical twoway video teleconferencing systems. As was described in a previous article [l], progress in LSI and digital signal processing have made band compression techniques and thus digital television transmission a present reality. Very high compression ratios have been achieved by using interframe coding. Codecs are now commercially available at 3 or 1.5 Mb/s. Beyond these techniques, “motion-compensated interframe coding” technology has been advanced, and is expected to double the data compression ratio. In this article, the principles of motion compensation and the present status of research and development are described.

A new IIR Nyquist filter with zero intersymbol interference and its frequency response approximation

Abstract: A new infinite impulse response (IIR) Nyquist filter with zero intersymbol interference is proposed. The necessary and sufficient conditions for the transfer function are obtained. The proposed IIR Nyquist filter requires only frequency-domain optimization. Multistep optimization, using the iterative Chebyshev approximation, is proposed. This method is able to design a new kind of IIR Nyquist filter with the minimum order. Numerical examples for 30- and 15-percent rolloff rates are illustrated. From these examples, it is confirmed that the IIR approach can reduce the filter order and hardware size, compared with the conventional finite impulse response (FIR) Nyquist filters. Its efficiency becomes marked for high Q Nyquist filters.

Synthetic aperture radar image processing system

Abstract: In an SAR image processing system of the type wherein an image is reproduced from received data, the reproduced image is obtained on the basis of range compression, range curvature compensation and azimuth compression, the correlation coefficient between two look image signals is determined for each of predetermined relative shift amounts, the relative shift amount K max giving the maximum correlation coefficient is determined, and an azimuth reference function and range curvature compensation function are generated based on the shift amount K.

A 32 kb/s toll quality ADPCM codec using a single chip signal processor

Abstract: An ADPCM codec, that can provide toll quality speech at a 32 kb/s transmission rate, has been implemented on a single chip signal processor. Maximum effort has been paid to design a robust adaptation scheme for a quantizer and a predictor to withstand transmission bit errors. The codec employs a simplified robust quantizer and also employs a new backward adaptive predictor. The decoder, including the new adaptive predictor, has a structure having fixed poles and adaptive zeros, attaining both high prediction capability and robustness. The performance of a developed codec, which has analog interface capability through a PCM codec chip, satisfies the standard 64 kb/s PCM performance specification in CCITT recommendation G.712.

Novel device isolation technology with selective epitaxial growth

Abstract: A fine device isolation technology for small geometry VLSIs using selective epitaxial growth (SEG) is described. The epitaxial silicon layer is selectively grown on a bulk silicon surface surrounded with a SiO 2 isolation wall under reduced pressure using SiH 2 Cl 2 -H 2 -HCl systems. Polysilicon gate MOSFETs are successively fabricated on the epitaxial silicon layer. The p-n junction characteristics are reasonable, according to theoretical values, and the leakage current along the lateral SiO 2 wall is negligibly small. The subthreshold characteristics for parasitic devices with submicron geometry gives the same slope value as that for conventional devices.

Holographic laser scanners using generalized zone plates.

Abstract: Aberration properties in holographic zone plates for use in laser scanners are investigated. A generalized holographic zone plate is proposed. To generate the zone plate hologram, holographic optical product operations between plural coherent spherical waves, are applied. When spherical waves, N in number, are applied, aberration can be corrected in a scan length magnification equal to or less than N2. Experimentally, a remarkable aberration correction effect for this hologram generation method is demonstrated for over 50-cm scan length. The configuration and features are described for the developed point-of-sale (POS) scanner employing generalized zone plate holograms.

System for demodulation of phase-shift keying signals

Abstract: in a system for demodulation of phase shift keying signals with a bandpass filter (6a) adapted to regenerate a carrier wave from a phase shift keying signal, there are provided means (8) for detecting phase variations in the regenerated carrier wave from the demodulated signal (e 1 , e 2 ), and means (8, 6a) for controlling the phase of the carrier wave being passed through the filter (6a) on the basis of the detection output (e c ) of the phase variation detecting means (8).

Double channel planar buried heterostructure laser

Abstract: A buried heterostructure semiconductor laser diode with improved efficiency, CW operating temperature and output characteristic is comprised of a semiconductor substrate of a first conductivity type and includes successively at least a first cladding semiconductor layer of the first conductivity type, an active semiconductor layer, and a second cladding semiconductor layer of a second conductivity type. The active semiconductor layer has a narrower bandgap than those of the first and second cladding semiconductor layers. The multilayer double heterostructure has a stripe geometry with channels formed along both sides of the stripe and extending down to the first cladding layer. A current blocking layer is formed on the multilayer double heterostructure except for the top surface of the stripe geometry, in order to block a current flow therethrough.

Permuted difference coefficient realization of FIR digital filters

Abstract: A new realization for FIR digital filters, using permuted difference coefficients, is proposed in this paper. Its coefficients are obtained as the difference between the successive values of the original coefficients reordered in a sequence with falling magnitude. The proposed realization can hold desirable properties in FIR filters, such as an exactly linear phase characteristic and stable implementation, and is effectively applied to a wide range filter response. Quantization error analysis shows that the internal data word lengths must be somewhat increased to maintain the same roundoff noise as in a direct form realization. Computational complexity becomes about 23 percent and 18 percent for 99th- and 299th-order filters, taking the excess data word lengths into account, compared with the direct form.

A Study on Intrinsic Gettering in CZ Silicon Crystals: Evaluation, Thermal History Dependence, and Enhancement

Abstract: Intrinsic gettering and thermally induced microdefects in CZ silicon wafers taken from various portions of seed to tail of crystal ingots have been studied by means of infrared absorption, an etching procedure, and transmission electron microscopy. Thermal history dependence and critical annealing conditions to enhance intrinsic gettering were evaluated. Two standard crystals grown under the same conditions except the thermal history after growth were investigated. It is found that the thermal behavior of inner defects and the effectiveness of intrinsic gettering strongly depend on the thermal history of crystal ingots. It also follows that the effectiveness of intrinsic gettering can be enhanced even in low oxygen wafers taken from the tail portion, when the first annealing procedure is appropriately carried out.

Monolithic analog adaptive equalizer integrated circuit for wide-band digital communication networks

Abstract: This equaliser is presented with particular emphasis on architecture and performance. To reduce the size, cost, and power dissipation, and to improve the operation speed and performance, this equalizer IC employs many techniques such as all analog signal processing with parallel updating the weights and eliminating the offset according to the least mean-square algorithm, MOS VLSI fabrication process and switched capacitor technique. As the key building blocks, low- and high-speed MOS operational amplifiers and four-quadrant analog multipliers are specially developed. The 16 mm/SUP 2/ chip providing 5 taps operates on /spl plusmn/5 and 10 V power supplies with power dissipation of 570 mW. The maximum data rate is more than 200 kHz. For the linear adaptive equalizer configuration operating at a data rate of 100 kHz, the residual RMS distortion and convergence time are measured to be -40 dB and about 2 ms (200 iterations), respectively, when a binary signal with an initial RMS distortion of 40 percent (-7.96 dB) is applied.

24- and 120-Channel Transmultiplexers Built with New Digital Signal Processing LSI's

Abstract: Two new digital transmultiplexers intended for commercial use have been developed. One transmultiplexer performs a bilateral conversion between two 12-channel FDM group signals and a 24-channel PCM carrier signal. The other mutually connects two 60Channel FDM supergroup signals and five 24-channel or four 30channel PCM signals. Both exploit a block processing digital SSBFDM multiplex/demultiplex scheme employing a cascade of an FFT processor and a set of complex coefficient digital filters. They have been built using newly developed high-level DSP LSI chips. Algorithmic considerations, developed LSI architecture, and equipment configuration are described as well as digital processor design details and measured performance.

Antenna apparatus including frequency separator having wide band transmission or reflection characteristics

Abstract: An antenna having a frequency separator of the type comprising plural lattice structures of a periodic conductive pattern. Each lattice structure exhibits an inherent resonance frequency and an inductance-capacitance effect at frequencies below the inherent resonance frequency. The periodic conductive patterns are selected so that each of the lattice structures exhibits substantially the same inherent resonance frequency, and when placed at selected intervals, the plurality of lattice structures exhibit interactive resonance at frequencies below the inherent resonance frequencies. Each lattice also exhibits substantially equal inductance and capacitance with respect to obliquely incident electromagnetic waves in the TE and TM modes.

High-Speed Digital and Analog Parallel Transmission Technique Over Single Telephone Channel

Abstract: A new technique for parallel transmission of digital and analog signals over a single telephone channel is presented. The modulation scheme treated in this paper is quadrature amplitude modulation, wherein the digital and analog information are mapped separately as in phase and quadrature components. In the realization of the high-speed parallel transmission, adaptive equalization and carrier phase control are significant problems. In the hybrid QAM modem a two-dimensional error signal cannot be measured accurately at the demodulator output. This causes difficulty in implementing the conventional decision directed circuitry, which is usually employed in the adaptive equalizer and the carrier phase control circuit. The new decision directed schemes which are applicable to parallel transmission are derived by using an error signal measurement defined independent of the analog part. Computer simulation for the parallel transmission scheme of 4.8 kbit/s digital and 2.4 kHz sampled analog sequences is carried out for a typical dispersive telephone channel. Simulation results show that this scheme is useful for high fidelity analog signal transmission.

Pulse signal processing circuit having a protection circuit against over-current breakdown

Abstract: For protection of an output switching transistor used in a pulse signal output circuit, the present invention provides a first detector for detecting over-current flowing through the output switching element, a second detection circuit for producing a detection signal in response to detection of over-current by the first detector in excess of a predetermined rate, and a protection circuit protecting the output switching element by suppressing the current flowing therethrough in response to the detection signal. The protection circuit may suppress the current flowing through the output switching element by both the output of the over- current detector and the detection signal.

Radio communication receiver having an oscillator circuit of lower power-consumption

Abstract: A radio paging receiver having two power sources, a receiver, a decoder and an oscillator, provides power from the lower of the two voltage sources to the oscillator when the paging receiver is turned off and provides power from the higher of the two voltage sources to the oscillator when the paging receiver is turned on. The oscillator provides higher power pulses to the decoder immediately upon the turn on of the pager thereby providing an immediate normal tone sound from the paging receiver.