Abstract: It is axiomatic that frequency changing, whether it be in communications or power convertors, can only be achieved by a process of modulation. The paper presents a powerful method of analysing and synthesising these complex modulation processes using a 3-dimensional modulation-model approach, which provides a lucid geometric interpretation of the processes involved. The application of the new approach is demonstrated by deriving new frequency-spectra results for the p.w.m. and p.a.m. convertors, thereby providing essential design information.

Abstract: This paper describes the microwave performance of GaAs FET's with two 1-mu m Schottky-barrier gates (dual-gate MESFET). At 10 GHz the MESFET, with an inductive second-gate termination, exhibits an 18-dB gain with --26-dB reverse isolation. Variation of the second-gate potential yields a 44-dB gain-modulation range. The minimum noise figure is 4.0 dB with 12-dB associated gain at 10 GHz. Pulse modulation of an RF carrier with a 65-ps fall ad a 100-ps rise time is demonstrated. The dual-gate MESFET with high gain and low noise figure is especially suited for receiver amplifiers with automatic gain control (AGC) as an option. The MESFET is equally attractive for subnanosecond pulsed-amplitude modulation (PAM), phase-shift-keyed (PSK), and frequency-shift-keyed (FSK) carrier modulation.

Abstract: Pulse width modulation (P.W.M.) techniques, adopted in inverters for modern variable speed drives, allow an easy adjustment of the fundamental component of the output voltage.

Abstract: The performance of inverter drives, which use the pulsewidth modulated (PWM) technique to control motor applied voltage and frequency, are critically influenced by the choice of the modulation policy used in the control circuits. This paper deals with practical inverter drives for squirrel cage induction motors and presents some basic considerations on modulation requirements. The advantages and limitations of popular modulation methods are discussed, and an improved modulation scheme, which allows us to extend the practical speed range of PWM ac drives, is presented.

Abstract: A harmonic reduced pulse width modulation, variable speed transistor bridge inverter drive controls frequency and magnitude of stator voltage applied to an induction motor so as to maintain constant flux in the motor and permit maximum driving torque to be realized from the motor over a wide speed range. An oscillator generates a train of clock pulses whose frequency is proportional to an analog speed signal, and a three phase generator derives three phase reference waves having periods which include a predetermined number of clock pulses. A resettable volt/hertz integrator derives a train of ramp pulses which are synchronized to the clock pulses and vary in magnitude as a function of the integral of the output voltage from the bridge inverter with respect to time. The constant volt/hertz ramp signals are compared to first and second reference voltages to derive phase-displaced first and second control pulses. The fundamental output voltages of individual phases of the bridge are regulated in accordance with respective three phase reference waves, and pulse width modulating means switch the transistors in the phases of the bridge by two different width pulses whose leading edges are established by the clock pulses and whose trailing edges are respectively at the first and at the second control pulses and in such a manner that the bridge inverter applies twelve-step voltages to the motor stator windings in which the fifth and seventh harmonics are substantially eliminated and in which the voltage-to-frequency ratio is controlled to maintain constant flux in the motor.

Abstract: A transistor inverter drive provides variable frequency and variable voltage power to an electric motor and pulse width modulates a predetermined number of harmonic-reduced constant volt/hertz pulses per cycle of motor frequency to selectively vary the motor stator voltage so that constant torque over a wide speed range can be accomplished and increases the number of constant volt/hertz PWM pulses per motor frequency cycle at low motor speeds to boost the stator voltage and thereby compensate for decrease in magnetizing current and in torque which would otherwise occur at low frequencies Particularly, the drive has first and second oscillators for respectively deriving trains of first and second clock pulses whose frequencies vary at different rates as a function of an analog speed signal; a frequency switch which selects the higher frequency train of clock pulses; a volt/hertz integrator which derives ramp pulses whose leading edges are established by the pulses from the frequency switch and which vary in magnitude as a function of the time integral of the inverter bridge output voltage; a first comparator for deriving a first control pulse when each ramp signal becomes equal to a first reference voltage; a three phase generator for deriving three phase reference waves synchronized to the first clock pulses and displaced 120° and each of whose period includes a predetermined number of first clock pulses; and means for controlling the fundamental output voltages of individual phases of the inverter bridge in accordance with respective reference waves and including pulse width modulation chopping means for controlling conduction of transistors of the bridge inverter by variable width PWM pulses whose leading edges are at the output pulses from the frequency switch and whose trailing edges are at the first control pulses, whereby the number of PWM pulses in each fundamental voltage cycle is controlled by the higher frequency pulse train and provides a boost in motor terminal voltage at low motor speeds

Abstract: The performance of inverter drives, which use the voltage and frequency, are critically influenced by the choice of the inodulation policy used in the control circuits. This paper deals with practical inverter drives for squirrel cage induction motors and presents some basic considerations on modulation requirements. The advantages and limitations of popular modulation methods are distussed, and an improved modulation scheme, which allows us to extend the practical speed range of PWM ac drives, is presented.

Abstract: From the beinning, plate moduladon has been the dominant method of modulation used in commercial amplitude-modulation (AM) broadcast transmitters. Recently, however, alternate modulation schemes have been employed in commercial transmitters in growing numbers, namely, pulse-duration modulation (PDM), modified Doherty, and modified Chireix (Ampliphase). This paper discusses traditional plate modulation and compares it, critically, to the newer methods being employed. Performance parameters and economic factors of each of the systems are reviewed and compared. A tutorial approach is used.

Abstract: A method of line-by-line scanning liquid crystal dots at the intersections of signal and scanning lines arranged in a matrix form, a signal including a selective voltage enough to excite the liquid crystal dot into illumination and a bias voltage for averaging a cross talk voltage is applied to the signal line. The duration time or pulse width of the selective voltage may be varied in accordance with a desired tone level, so that a display with tone can be achieved while the cross talk voltage is averaged.

Abstract: Power control apparatus and method for controlling polyphase excitation of a polyphase load. A first sequence of timong pulses are generated to represent each zero level voltage crossing of every phase voltage from a polyphase voltage source. After each of the predetermined numbers of the timing pulses has been generated, an energizng pulse is generated having a width of a predetermined duration. A set of power switches is provided coupling the polyphase source to the load via a set of load lines. The power switches are all rendered conductive to selectively couple phase voltages from the polyphase source to the load by each energizing pulse. This causes excitation of the load via repeating sequences of intermittent power pulses, with each power pulse being comprised of a selected grouping of the phase voltages from the polyphase voltage source. The source phase voltages comprising each group are associated in time with one another on the load lines and are: (1) of a selectable number, and (2) of a selectable permutation of phases. Variance of the rate at which the energizing pulses are generated and of the value of the predetermined duration of the pulse width determines the selected number of and the phase of the voltages in the power pulses. The selected number and phases of the voltages in each power pulse and the repetition rate of the power pulses determine the effective frequency at which the load is excited. In a preferred embodiment the load is a polyphase induction motor, and its speed is fractionally reduced without a great sacrifice in torque by adjusting the repetition rate and the pulse widths of the energizing pulses.

Abstract: Instability effects over a wide range of static load current conditions in a conventional pulse width modulated (PWM) voltage regulator-converter/power converter circuit configuration having cascaded LC--LC filter networks are eliminated by replacing an inductor, in the averaging filter section of the voltage regulator-converter with the primary winding of a transinductor and by placing the secondary winding thereof in series with an inductor in the output filter section of the power converter. The aforementioned transinductor, in combination with other elements of the system, is designed and configurated such that the closed-loop stability characteristics approach that of a two pole system while maintaining the superior filtering characteristics of a four pole system.

Abstract: In an anti-skid type control system for automotive vehicles, apparatus for maintaining wheel slip in a region of values associated with a maximum coefficient of road friction. Periodic modulation of the wheel brake torque in conjunction with wheel acceleration measurement are employed to determine the variation of the coefficient of road friction from an optimum value, while integral-plus-proportional control of the pulse modulation allows compensatory variation of the wheel torque and slip condition to a condition providing the optimum coefficient of road friction.

Abstract: An optimization method, which will be of use in selecting the modulation technique and Carrier frequency for a PWM inverter system, is presented. The difficult decision, concerning the tradeoff between efficiency and unfiltered harmonic content, can be made with the help of this method. A relation between second-order filter rating and unfiltered harmonic attentuation, for optimum component values, is also obtained. The optimization method is used for illustration to select the optimum modulation technique and its carrier frequency for the modified McMurray inverter [1] to be used in a rapid transit auxiliary power converter. The design aim is to obtain a constant sine wave output with a specific input supply voltage variation. The inverter efficiency is predicted for various carrier frequencies using two modulation schemes. The Schonung and Stemmler [2] modulation approach, with a carrier frequency of 900 Hz, is found to be optimum as it results in low filter rating and an efficient inverter.

Abstract: In a closed loop electronic fuel injection control unit having a basic fuel schedule in response to engine operating conditions, the amount of oxygen in the exhaust gases is detected and compared with a desired value to provide an error signal. The error signal is shaped to form a series of binary pulses of alternating voltages of constant amplitude in correspondence with the plus and minus deviation from the reference voltage which represents the desired oxygen quantity. The binary pulses are amplified by a variable gain amplifier to provide a signal which is used to adjust the basic fuel schedule. The time duration of each binary pulse is measured by a counter to provide an output when a pulse width reaches a predetermined interval. The counter output is coupled to the amplifier to increase the amplifier gain to change the rate of fuel supply.

Abstract: A switching amplifier includes a pulse width modulator for converting a bipolar input signal, which may be a speech signal, into a train of unipolar pulses having durations which vary with the instantaneous absolute amplitude of the input signal. The pulses control the energizing of a series switch which supplies current to a switching bridge circuit. The switching arms of the bridge circuit are controlled by the polarity of the input signal. Another switch and several diodes are used to provide a path for output current when the series switch is open. The output current is filtered to remove fluctuations at the switching rate, and applied to a load. The amplified output voltage signal accurately follows the input signal, and the efficiency of conversion of DC power to AC output power can approach 100 percent, limited only by switching and filtering losses. A single polarity DC supply, such as a battery, is used to provide bipolar output current to an ungrounded load. High efficiency is maintained even with partially reactive loads, since the switching circuits return reactive power to the DC power supply.

Abstract: An inverter controlling device for eliminating higher harmonic components of lower ordinals from output voltage of the inverter is provided. The inverter is controlled such that each half cycle of a basic wave is divided into an even number of sections respectively having an equal phase interval, a pulse voltage is produced at the center of each of said sections so that the pulse width of the respective pulses in each said half cycle will be wider as they approach the center of the half cycle than that of the pulses at both ends with a predetermined ratio, and a plurality of pulse voltages similar to a pulse train of said pulse voltages is produced as an inverter output.

Abstract: Stability analysis and transient response predictions of PWM controlled DC/DC regulators are now feasible in both continuous and discontinuous mode A linear equivalent continuous model of the power stage is firstly established for the boost and the buck converter by means of state variable representation for each of the elementary structure occuring within one sampling period. This equivalent model turns out to be of first order for the discontinuous mode and of 2nd order for the continuous mode. A general computer program has been implemented for the derivation of such a model and for the stability analysis and transient response of multiloop regulators. Special emphasis has been given to the boost converter in light conduction mode operation whether an AC feedback loop is included or not. The existence of the non-minimum phase effect associated with such a regulator for a heavy operation mode is shown to be dependent of the sampling frequency.

Abstract: Presented is a converter philosophy for controlled transfer and transformation of electric energy through internal series resonant circuits at high internal power frequencies in excess of 10 kHz. Control of the continuously oscillating high Q series resonant circuit is attained by adjustment of the phase angle ψ r between the exciting voltage and the resonant current. Only a very small fraction of the energy transferred to the load is absorbed by the resonant circuits to replace the power dissipated therein. Moderate and unconditionally predictable voltage and current stresses on components result from definite control of static and dynamic behavior of the system. This system is suited for construction of failsafe and highly efficient, low cost, submegawatt, single module converters with use of currently available components.

Abstract: A system for fully characterizing monochromatic radiation incident on the stem. The system computes the azimuth and elevation of the point of origin, optical frequency, pulse width, power level and pulse repetition frequency of the source.

Abstract: PURPOSE:To prevent from receiving an electric shock by calculating errors with respect to respective set values of an output current and the output voltage and making a smaller one of both error signals to a switching element driving signal to control the output voltage or the output current to the set value CONSTITUTION:At the time of no-load, or when the output current is small, since an output signal of an output current detector 13 is zero or close to zero, the voltage error signal becomes small Accordingly, since the switching elements 2a and 2b are turned on with the pulse width of the duty ratio in accordance with the smaller error signal, the output voltage is restricted by the set value and made to almost a constant voltage characteristic When the output current increases, since the output of the output current detector 13 approaches the set value of an output current setting circuit 14, the current error signal becomes small Then, when the current error signal becomes smaller than the voltage error signal, the 'on' period width of the switching elements 2a and 2b is changed over so as to be decided by the duty ratio determined by the current error signal Accordingly, the output current is restricted by the value determined by the output current setting circuit 14 and made to almost the constant current characteristic

Abstract: A two-phase pulse signal generator which includes a first triangular signal generator in the form of a closed loop oscillator, a second triangular signal generator for generating a signal which is inverted with respect to the first triangular signal and a couple of comparators for comparing the respective triangular wave signals with a common control signal representative of a control requirement. The two-phase pulse signals are obtained from the respective comparators and the time duration of each of the pulse signals is proportional to the contrl voltage.

Abstract: A pulse width modulation circuit which comprises a mixer for combining an input audio signal with a feedback signal and for developing a difference signal to feed to an integration circuit. The integration circuit is coupled to a pulse width modulator which has a sawtooth carrier input for modulating the input audio signal. The resulting pulse modulated signal is then fed to a pulse amplifier and a low-pass filter and finally to a load. The output of the low-pass filter is coupled back to the mixer.

Abstract: An automatic surface defect-detecting method and apparatus for detecting only effective significant surface defects. The significant defects can be detected from video signals and differential signals corresponding to particular scanning lines respectively by removing the distributed density portions having a larger pulse width in the scanning line direction, or removing smaller differential value portions in density, from the examined portions with higher density of flourescent magnetic powders thereon.

Abstract: In a polyphase electric energy meter, voltages of the phases of a polyphase alternating power to be measured are utilized to subject an input pulse signal to be applied to a pulse distributor to pulse width modulation to form polyphase control pulses, which cyclically operate switches provided respectively for the phases so that an operation circuit cyclically receives the voltages and currents of the phases and produces a current output proportional to the sum of the electric powers of the phases.

Abstract: A circuit is provided to produce an output pulse for each analog input pulse whose amplitude and width fall within specified limits. A first amplitude comparator produces a first signal when the amplitude of one of the input pulses exceeds a first reference amplitude and a second amplitude comparator produces a second signal when the width of the one of the input pulses has an amplitude exceeding a second reference amplitude different than the first reference amplitude. Digital circuitry is coupled to the second amplitude comparator to convert the second signal into a binary count, to produce a third signal when the count is greater then a minimum pulse width reference count and to produce a fourth signal when the count is less than a maximum pulse width reference count. A logic gate and pulse generator is coupled to the first amplitude comparator and the digital circuitry responsive to the simultaneous presence of the first, third and fourth signals to produce the circuit output pulse. A system employing a plurality of the above described circuits enables the production of a system output pulse for each analog input pulse whose amplitude and width fall within a given range of amplitudes and a given range of widths with each of the plurality of the above-described circuits having different first and second reference amplitudes to cover the given range of the amplitudes and widths.

Abstract: In a pulse-echo ultrasonic circuit an ultrasonic search signal is periodically transmitted into a workpiece. The ensuing pair of echo signals (entrant and rear surface reflection respectively) are fed to a timing circuit for providing a timing signal responsive to the time interval between the two echo signals. A fixed pulse width pulse generator is triggered responsive to the search signal. The output from the fixed pulse width generator and the timing signal from the timing circuit are selectively fed to a converter circuit for providing an output signal indicative of workpiece thickness or workpiece acoustic velocity. The converter circuit includes adjustable parameters comprising current magnitude and resistance to provide suitable calibration. Similar calibration is achieved also by varying the repetition rate of the search signal.

Abstract: A system for high-density data recording at low tape speeds receives a unipolar signal representing encoded digital data and transforms it to a bipolar signal having a constant pulse width. The low-frequency response required of the system is minimized because the power spectrum of the signal is altered through a time domain transformation. The narrow bandwidth enables the use of very low tape speeds at high bit packing densities. Tape speeds of 15/32 ips or less at densities about 20 thousand (k) bits per inch (BPI) are possible. The spectrum of the transformed code has no direct current (DC) component which eliminates the need for a base line compensator in the reproducing portion of the system.

Abstract: By using a Schottky-barrier-gate Gunn-effect digital device the direct modulation of a GaAs-Al x Ga 1-x As double-heterostructure laser was achieved with a rise time of 250 ps. The dependence of the optical waveforms on the bias-current levels was investigated in detail. The results are compared with a rate-equation analysis. A discrepancy between the present theory and the experiment indicates the existence of an additional relaxation mechanism.

Abstract: Three modifications of time-division multipliers have been investigated with respect to their response to ac and dc input quantities. These investigations were part of the development of an electronic ac-dc power comparator and were carried out by aid of a computer (Siemens type 4004). The calculations take into account different values of power factors, sample rates, amplitudes and different signal phases with respect to the first sample pulse. Results are presented in form of graphs and tables.