Showing papers by "NEC published in 1977"

Echo Canceler with Two Echo Path Models

Abstract: An adaptive echo canceler with two echo path models is proposed to overcome the false adaptation problem for double-talking. The echo canceler possesses two separate echo path models (EPMs), one (background EPM) for adaptively identifying echo path transfer characteristics and the other (foreground EPM) for synthesizing an echo replica to cancel out echo. The parameter values of the foreground EPM are refreshed by those of the background EPM, according to a transfer control logic, when the logic determines that the background EPM is giving a better approximation of echo path transfer characteristics than the foreground EPM. Completely digital hardware implementation is described. Using the hardware, it is shown that virtually complete double-talking protection is actually realizable by the new method.

Transient colour centres caused by UV light irradiation in yttrium aluminium garnet crystals

Abstract: The degrading laser oscillation behaviour in YAG crystals is attributed to the production of colour centres, induced by UV light irradiation. The optical absorption spectrum of UV induced colour centres is investigated using time resolved transient absorption spectroscopy technique. The UV generated spectrum is found to consist of the superposition of three broad absorption bands E1, E2 and E3 peaked near 1.2 × 104, 2.0 × 104, and 2.8 × 104 cm−1, respectively. Various experiments, such as additive coloration, ESR, thermoluminescence, and optical absorption measurement are made. On the basis of experimental results, a model is proposed for the E1, E2 and E3 bands, which are explained by colour centres trapping an electron at an anion vacancy site. Das sich verschlechternde Laserverhalten in YAG-Kristallen wird der Bildung von Farbzentren zugeschrieben, die sich durch UV-Einstrahlung bilden. Das optische Absorptionsspektrum von UV -induzierten Farbzentren wird mit der zeitaufgelosten Absorptionsspektroskopie untersucht. Es wird gefunden. das das UV-erzeugte Spektrum aus der Uberlagerung von drei breiten Absorptionsbanden E1, E2 und E3 bei etwa 1,2 × 104, 2,0 × 104 bzw. 2,8 × 104 cm−1 besteht. Verschiedene Experimente, wie zusatzliche Verfarbung, ESR, Thermolumineszenz und optische Absorptionsmessungen werden durchgefuhrt. Auf der Grundlage der experimentellen Ergebnisse wird ein Modell fur die E1-, E2- und E3- Bande vorgeschlagen, das Farbzentren annimmt, die ein Elektron in einer Anionenleerstelle einfangen.

Echo cancellation in the telephone network

Abstract: Most long-distance telephone connections generate echoes, which must be heavily attenuated in order to obtain satisfactory transmission quality. Voice-actuated switches (echo suppressors) are widely used to eliminate echoes but have an unfortunate tendency also to cut out part of the desired signal from the other end of the line. Because the distortion caused by echo suppressors is particularly noticeable on satellite-routed connections, the advent of telephone communication via satellite, including the recent introduction of satellite circuits into the U.S. domestic network, has motivated the search for a better way to eliminate echoes. The answer may be the echo canceler, an adaptive filter which selectively eliminates echoes. Advanced echo canceler designs have been undergoing field trials in recent years. This article explains why echo cancelers are advantageous and how they work.

Semiconductor device having a miniature junction area and process for fabricating same

Abstract: In a method for fabricating a semiconductor device, a polycrystalline film deposited on a main surface of a substrate is subjected to selective oxidation to form polycrystalline silicon electrode wiring paths separated by silicon oxide. An impurity of a conductivity type opposite to that of the substrate is introduced through at least one of the wiring paths into the substrate. Also disclosed is a novel semiconductor device fabricated according to this process which has a reduced junction area and a shortened junction-to-electrode distance.

Grain-size effects on microwave ferrite magnetic properties

Abstract: This paper presents a review of polycrystalline microwave ferrites with specific reference made to the grain size. Fine-grained ferrites and large-grained ferrites as referred to in this article stand for the ferrites with an average grain size of 2 μm or less and those of 100 μm or larger, respectively. Fine-graining of ferrites is one of the state-of-the-arts techniques for obtaining high-power ferrites. Large-graining is a newly developed technique for further improving the family of narrow resonance linewidth garnet materials. Starting with some ceramics-oriented topics including the definition of the average grain-size and so forth, the present review covers the grain-size dependence of initial permeability and the grain-size dependence of microwave properties (ΔH, ΔH eff , and ΔH k ) both in the theoretical and in the experimental phases. Successful device applications of newly developed "single-crystal-like" large-grained ferrites are also reviewed.

Unstable horizontal transverse modes and their stabilization with a new stripe structure

Abstract: Kinks in the light output and other anomalous characteristics in stripe-geometry lasers were studied. It was found that these anomalies were caused by unstable horizontal, parallel to the junction, transverse modes. Introduction of a refractive-index guiding by Zn-diffusion stabilized the horizontal mode and removed the kink and other anomalies completely.

Ceramic compositions having high dielectric constant

Abstract: A ceramic composition allowing low-temperature sintering at a temperature below 1000° C and having a high dielectric constant over 5000 essentially contains Pb(Fe 2/3 W 1/3)O 3 and Pb(Fe 1/3 Nb 2/3)O 3 , in which the molecular ratio of Pb(Fe 2/3 W 1/3)O 3 to Pb(Fe 1/3 Nb 2/3)O 3 ranges from about 0.2 to 0.5.

Numerically controlled machine comprising a microprogrammable computer operable with microprograms for macroinstructions and for inherent functions of the machine

Abstract: With a microprogrammable computer of a numerically controlled machine, macroinstructions are executed in response to a first microprogram. The computer makes the machine carry out its inherent functions, such as interpolation, in response to a second microprogram. Flags may be used to switch sequential execution of the macroinstructions to repeated execution of a portion of the macroinstructions and sequential execution of microinstructions of the second microprogram.

An Analysis of Jitter Accumulation in a Chain of PLL Timing Recovery Circuits

Abstract: This paper analyzes the timing jitter accumulation which is produced in a chain of regenerative repeaters when a second-order phase-locked loop (PLL) is used as a timing filter. In a PLL timing recovery circuit, the growth of timing jitter varies with the value of damping factor \zeta . In this paper, therefore, approximate equations of timing jitter accumulation are given with respect to a case in which \zeta is sufficiently large, and the timing jitter is calculated with a digital computer for various values of \zeta . It is shown that, when \zeta is sufficiently large, results similar to those for first order loops or single tuned circuits are obtained, i.e., the meansquare random jitter is almost proportional to the square root of the number of repeaters, and the mean-square systematic jitter is almost proportional to the number of repeaters. When \zeta is small the meansquare jitter increases exponentially as the number of repeaters is increased. This paper also describes the optimum value of \zeta , considering both the jitter accumulation and the transient response of the PLL, by using the number of repeaters N as a parameter. As a result, it is postulated that the optimum value of \zeta is 5 to 8 when N is 100, and 15 to 18 when N is 1,000.

Constant current density plating method

Abstract: In the present plating method the bath contains an electrolyte solution having a uniform ion concentration. A common electrode, a plating electrode and a standard electrode are arranged in the bath. A direct current source is connected between the common electrode and the plating electrode. A further, constant, direct current source is connected between the common electrode and the standard electrode. A potentiometer device is arranged for detecting resistance changes between these electrodes due to variations in the ion concentration and in the mobility of the electrolyte solution between the electrodes. A control is responsive to the potentiometer device for regulating the plating current supplied by the direct current source as a function of the potential difference detected by the potentiometer device, whereby a constant plating current density is achieved.

Electronic key telephone system

Abstract: An electronic key telephone system is disclosed that provides a plurality of telephone features and functions, while only requiring a four-wire line between the central equipment and each key-set telephone (KST) and a two-wire line between the central equipment and each single-line telephone (SLT). Linear delta coding and time division multiplex (TDM) techniques are used to eliminate the multiple pairs required in traditional private business exchange (PBX) systems between the remote key telephones and the control unit. In the present system, a microprocessor controlled TDM controller transmits and receives control signals serially to and from interfaces in the system for control purposes and also for establishing exchange of digitized audio information data between selected interfaces. The system thus exchanges digitized audio information directly between interfaces and provides control signalling between the TDM controller and the interfaces, with all of the exchanges being done in real time. Among other things, the system is compatible with all types of existing central office exchange lines. The system may use combinations of single-line telephones (SLTs) or key-set telephones (KSTs). Specialized functions, such as conference calls, background music, external zone paging and night chime, as well as on-line maintenance, system configuration reprogramming, out-going telephone call control, and recordkeeping are available. To reduce complexity and increase economy, several functions in the system are time-shared, and the system is constructed in modular form to allow its capabilities to be tailored for its intended use.

Memory circuit with protection circuit

Abstract: A memory circuit with protection circuit having particular application to MOS-IC memories is disclosed. The protection circuit prevents the memory from being damaged by an undesirable turn-on or turn-off sequence of main and substrate voltage supplies or by an abnormal substrate voltage.

A large-signal analysis of broad-band klystrons with design applications

Abstract: For the design of a high-performance broad-band klystron, an accurate large-signal analysis is made. By a one-dimensional analysis program using a disk model of the electron stream, the interaction between a bunched electron beam and the electric field in each cavity gap is studied, taking into consideration space-charge forces, relativistic effects, and electric field distributions in ungridded gaps; beam loading is included by an iterative method at each intermediate gap, and the energy exchange in the output gap is obtained from the change in kinetic energy. On the five-cavity UHF-TV klystron designed with this program and having a conversion efficiency of over 60 percent, the debunching effect of the electric field in intermediate cavity gaps and the behavior of vibrating electrons in the output gap are clarified. Calculated conversion efficiency is shown to agree well with measured efficiency over the pass-band. Additionally, by a two-dimensional analysis program, the effect of the cathode magnetic coefficient on the electron bunching is studied.

Automatic machining system

Abstract: An automatic machining system incorporating all the features of a numerically controlled type machine while eliminating the need for paper tapes. The tool receiving head incorporates means for identifying the moment of contact between tool and work piece, avoiding the need for inputting start position data. Motion control and drive means are provided for X, Y and Z head movement. The novel design provides drilling or punching by insertion of the proper tool in a head adapted to receive either tool. Visual displays provide step by step directions and allow for selection of the machining operation and sequential execution of the machining steps in accordance with inputted data requested by the display. The punching tool operates automatically simply under control of Z axis movement.

Improved noise performance of GaAs MESFET's with selectively ion-implanted n + source regions

Abstract: Superior microwave performance of 0.5-µm-gate GaAs MESFET's has been attained by a structure with selectively ion-implanted n+source regions. The source series resistance is reduced and the noise figure of 2.1 dB is observed at 12 GHz.

A.C. power supply circuit with surge current suppression

Abstract: The current surge, normally associated with the initial application of a nominal AC current to an inductive load, is prevented by preventing the magnetic core of the inductive load from being driven into saturation Initially, the current is half wave rectified and amplitude limited The amplitude limitation insures that the core will not be driven into saturation A voltage detector connected across the inductive load senses only the counter EMF of a polarity opposite to the polarity of the half wave current When the sensed voltage reaches a predetermined value, a direct connection is provided between the AC supply and the inductive load, bypassing the half wave rectifier and the amplitude limiter

Analytic expressions for the side fringe field of narrow track heads

Abstract: The side fringe field of narrow track heads, which plays an important role at very high track densities, has been analyzed, and some analytic expressions for the three-dimensional field distribution obtained. An expression for the recorded track width based upon these results is also discussed.

System for detecting by a first pilot and a group of second pilots correlated to the first a frequency and/or phase difference between relayed carriers

Abstract: A plurality of pilot signals having predetermined relations are used to remove a phase-frequency difference introduced into transmission signals by one or more repeaters in a high frequency radio link. The pilot signals are also used to compensate for crosstalk introduced into respective pairs of said transmission signals.

Decoder for error-correcting code data

Abstract: An error correcting decoder is disclosed which blocks correction of bits received during periods of relatively high signal intensity levels. A syndrome register and decision circuit provide error correcting bits for all bits which the sequence of input data determines to be in error. But only those data bits which occur during low levels of signal intensity are corrected.

Clock extraction device for double-binary phase-shift keying system

Abstract: A circuit for extracting a clock signal from a double-binary phase-shift keying system is disclosed. The carrier wave form is regenerated at the receiver from the phase-shift keyed (PSK) signal input. The regenerated carrier wave is frequency doubled and frequency mixed with the PSK input signal which has also been frequency doubled. A desired clock signal is thereafter extracted from the mixed signal by a band-pass filter. The system does not include a frequency divider which would result in a phase ambiguity.

A simple model for short channel MOSFET's

Abstract: A model for short channel MOSFET's is presented. The model is simple in spite of taking 2-dimensional (2-D) effects into account. Predicted I-V characteristics are in good agreement with experimental results. This model can be utilized in circuit analysis programs.

A New Microwave Amplitude Limiter Using GaAs Field Effect Transistor

Abstract: This paper describes a new microwave amplitude limiter with low AM-to-PM conversion using a class A GaAs FET amplifier. It has been experimentally established that this limiter is applicable for use with 200 Mbits/sec 4-phase PSK signals or 2700-channel FDM-FM signals.

Optimum waveform design and its effect on the peak shift compensation

Abstract: An equalization method of reducing peak shift caused by the intersymbol interference is presented to obtain high density digital magnetic recording First, a new ideal frequency characteristic is determined to get an impulse response free from peak shift Then, using the equalizer that gives this response, the extent of the peak shift compensation is simulated with a computer When a 2200BPI (FM) disk unit is used to double the bit density with MFM, it is found that the peak-shift in the worst case is only 84% of the full phase margin Here, other parameters such as RPM, remain constants However, as the application of the equalizer increases the noise power, signal to noise ratio of the input signal is required to be sufficiently high When the equalizer is applied to a 4040BPI (MFM) disk unit at the same density, phase margin for data separation increases, because the decrease in peak shift seems to be greater than the increase in the noise power

Tape tension control for tape recording and/or reproducing system

Abstract: A purely electrical tension control system utilizing the characteristics of a shunt motor coupled with the supply reel. In a recording or reproducing mode, the reel drive motor is forced to rotate in a direction opposite to its normal direction of rotation, thus producing a counter electromotive force and torque for rotation. The counter electromotive force is detected and employed to control the motor torque to thereby maintain a fixed tape tension.

Turret type television tuner

Abstract: The present turret type television tuner comprises a U-shaped chassis having first and second end walls joined by a side wall. A main channel selecting shaft is supported in said end walls. A toothed index wheel is mounted on the selector shaft adjacent the first end wall. A fine tuning shaft is mounted concentrically around the selector shaft. A fine tuning drive includes a first driving gear mounted concentrically on the fine tuning shaft and a second driving gear mounted on a pivotally mounted member on the second end wall. A coupling clutch permits a fine tuning operation. A torsion bar spring member including a bail portion is mounted on the first and second end walls, whereby a first resilient arm of the spring member extends along the first end wall to engage the toothed index wheel, while a second resilient arm portion extends along said second end wall to engage the selector shaft and bias it against its bearing surfaces. A rotatable turret includes a plurality of coil units and supporting discs fixed on said main shaft. Each of the coil units includes an elongated bar and coils making up a tuned circuit for each stage. The inductance of at least one of the coils is adjustable for fine tuning. A stator includes a printed circuit board and a stator bar having a plurality of spring contacts cooperating with selected coil units. The second resilient arm of the spring member provides a bias force against the selector shaft in a direction opposite to that of the spring contacts of the printed circuit board on the stator.