Low Impedance Load Research Articles

TWACS??, A New Viable Two-Way Automatic Communication System for Distribution Networks. PART II: Inbound Communication

A new concept of two-way automatic communication for distributed systems, henceforth abbreviated as TWACS??, is introduced in this paper. This paper restricts itself to the discussion of inbound signalling from the remote transponder units at the customer's premises to the receiver located at the substation. Inbound signalling uses current pules, precisely generated and limited to only a small segment of a half cycle of the 60 Hz wave. The inbound signal is detected in the neutral or phase bus conductor at the substation. Bit coding, multichannel assignment, detection algorithms and propagation characteristics are explained and discussed and the paper concludes with field results obtained at many different utilities. A previous companion paper [1] presents the basic functions and features of TWACS?? and describes outbound communication. This paper focuses on TWACS?? inbound communication and presents the subject as follows: ??? general description of TWACS?? inbound communication technology, ??? signal generation and propagation, ??? signal detection, ??? bit coding and multichannel signalling, ??? noise characteristics, ??? error correction and detection, ??? field experience. Using a block diagram of a typical TWACS?? installation, the operation, synchronization and performance of inbound communication is introduced. Inbound signals are generated by drawing current pulses at the remote transponder units. The actual transmitter consists of a low impedance load inductor and a pair of anti-parallel connected SCRs in parallel with the 240 V line. By limiting the on time of the SCRs the amplitude and duration of the current pulses can be controlled.

Large swing CMOS power amplifier

A CMOS class AB power amplifier is presented in which supply-to-supply voltage swings across low-impedance loads are efficiently and readily handled. The amplifier consists of a high-gain input stage and a push-pull unity-gain amplifier output stage. The amplifier dissipates only 7 mW of DC power and delivers 36 mW of AC power to a 300-/spl Omega/ load, using standard power supplies of /spl plusmn/5.0 V. Lower impedance loads can be driven to higher power levels, providing the internal current limiting level is not exceeded.

TWACS, A New Viable Two-Way Automatic Communication System for Distribution Networks. Part I: Outbound Communication

A new concept of two-way automatic communication for distributed systems, henceforth abbreviated as TWACS??, is introduced in this paper. This paper restricts itself to the discussion of inbound signalling from the remote transponder units at the customer's premises to the receiver located at the substation. Inbound signalling uses current pules, precisely generated and limited to only a small segment of a half cycle of the 60 Hz wave. The inbound signal is detected in the neutral or phase bus conductor at the substation. Bit coding, multichannel assignment, detection algorithms and propagation characteristics are explained and discussed and the paper concludes with field results obtained at many different utilities. A previous companion paper [1] presents the basic functions and features of TWACS?? and describes outbound communication. This paper focuses on TWACS?? inbound communication and presents the subject as follows: ??? general description of TWACS?? inbound communication technology, ??? signal generation and propagation, ??? signal detection, ??? bit coding and multichannel signalling, ??? noise characteristics, ??? error correction and detection, ??? field experience. Using a block diagram of a typical TWACS?? installation, the operation, synchronization and performance of inbound communication is introduced. Inbound signals are generated by drawing current pulses at the remote transponder units. The actual transmitter consists of a low impedance load inductor and a pair of anti-parallel connected SCRs in parallel with the 240 V line. By limiting the on time of the SCRs the amplitude and duration of the current pulses can be controlled.

Sensitivity of Crosstalk in Twisted-Pair Circuits to Line Twist

The prediction of crosstalk induced in an unbalanced twisted pair by an adjacent transmission line is investigated. The induced voltage at one end of the twisted pair is shown, experimentally, to be extremely sensitive to twist for low-impedance loads and relatively insensitive to twist for high-impedance loads. Ex- perimental results are given which show that a slight rotation of one end of the twisted pair ( no more than 1800) can cause a change of as much as 35 dB in the induced voltage. The consequence of these results is that, in a practical situation, one would therefore not be able to predict this crosstalk for low-impedance loads with any con- sistency. A simple model explaining these results is given.

Low-inductance, low-impedance megawatt average power load

A compact, low-inductance, 0.5-Ω, 1-MW average power resistive load has been developed to facilitate testing of the MAPS-40 thyratron. The flowing liquid electrolyte system uses the large thermal mass of a storage tank of electrolyte to store the energy which is dissipated through a heat exchanger after the high-power run. The electrolyte starting temperature, flow rate, and allowable temperature rise determine the maximum average power into the load; the external and internal spacings and flow uniformity determine the maximum peak power; the flow rate and storage volume determine maximum running time. The load assembly consists of two parallel glass pipes 10.2 cm in diameter and 15.25 cm long. The active volume in each pipe is 6.35 cm long and is contained between electrodes 8.9 cm in diameter. The two sections of the load are electrically in parallel and flowing in series, putting both flow connections at ground potential. The major problem was getting the internal flow pattern uniform to eliminate local boiling and arcing across the bubbles while keeping the pressure drop low and flow high. The calculated inductance of the load assembly is 11 nH, and the structure lends itself to coaxial connections which reduce the overall inductance still further. Material compatibility with the electrolyte will be discussed.

The wedged transducer — A transducer design for broad band characteristics

This paper presents a method of increasing the bandwidth of transducers feeding low acoustic impedance loads such as fluids and of electrically matching them over the full bandwidth. It consists of interposing between the transducer and the actual load, a wedge made out of a material having the desired acoustic impedance. The wedge angle is chosen such that no reflected wave from the wedge-load interface can return to the transducer. In this manner, the effective load seen by the transducer is that of the wedge itself, regardless of the actual load. The appropriate electrical matching is achieved by means of a hybrid band pass filter containing both electrical and mechanical components, with the transducer as an integral part. Experimental results on a 4-inch diameter PZT-4 transducer, coupled to water through a brass wedge, demonstrate a bandwidth of 75 percent and an insertion loss of 8.5 dB, well in accordance with theory, Without the wedge, the bandwidth would be only 3.2 percent.

The wedged transducer--a transducer design for broad band characteristics.

This paper presents a method of increasing the bandwidth of transducers feeding low acoustic impedance loads such as fluids and of electrically matching them over the full bandwidth. It consists of interposing between the transducer and the actual load, a wedge made out of a material having the desired acoustic impedance. The wedge angle is chosen such that no reflected wave from the wedge-load interface can return to the transducer. In this manner, the effective load seen by the transducer is that of the wedge itself, regardless of the actual load. The appropriate electrical matching is achieved by means of a hybrid band pass filter containing both electrical and mechanical components, with the transducer as an integral part. Experimental results on a 4-inch diameter PZT-4 transducer, coupled to water through a brass wedge, demonstrate a bandwidth of 75 percent and an insertion loss of 8.5 dB, well in accordance with theory. Without the wedge, the bandwidth would be only 3.2 percent.

Design Of Multiple Slug Circuits For Microwave Solid-State Sources

A procedure for designing multiple slug circuits, suitable for microwave solid-state oscillators, is presented. Expressions for slug impedances required to match a low impedance load are derived. Impedance ranges that can be possibly matched by various slug circuits are identified. It is shown that a low discontinuity slug can be used for fine variation of circuits parameters. Slug circuit is also considered as a coupling structure for a resonant cavity. Multiple slug circuit is analysed by the theory of small reflections and an expression for its bandwidth is thus derived.

An EBS (electron bombarded semiconductor) high-current pulse amplifier

An EBS (electron bombarded semiconductor) pulse amplifier which generates high-current fast-risetime variable-width pulses into low impedance loads is described. Current pulses of 100 A into a 1-Ω load have been obtained with a risetime of 2.2 ns. A di/dt of 40 000 A/µs and a dV/dt of 71 000 V/µs have been obtained. Pulse lengths to 1 µs at 0.1-percent duty have been achieved. The risetime and peak current capabilities are presently limited by internal circuit parasitics. Without parasistics, the theoretical peak output capabilities for this EBS are 340 A with a di/dt of 6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> A/µs.

Computer simulation of radiation induced emitter crowding

Radiation induced emitter crowding effects can precipitate an anomalous photocurrent response. Such a response would not be predicted by the usual computer simulation using a charge control representation of a bipolar transistor equipped with a primary photo-current source. Radiation induced emitter crowding effects are prevalent in large epitaxial power transistors which operate with low impedance loads where large photocurrent s are observed as a result of irradiation. A model has been developed which simulates radiation induced emitter crowding and it is applicable to most existing circuit analysis codes. Experimental data obtained from pulsing 50 watt silicon epitaxial power transistors with 50 nanosecond and 8 microsecond linear accelerator pulses in the electron beam mode show excellent agreement with the predicted results.

Efficient 100 Mb/s driver for electroluminescent diodes

Abstract The application of high-radiance electroluminescent diodes in optical communication systems will require efficient, high-current, high-speed modulation circuits capable of driving the low-impedance diode load. A technique which has proved to ho useful in driving such diodes at a 100 Mb/s rate, using a two-stage transistor emitter-follower circuit and a suitable matching network, is described.

A Fast High Current Pulser Suitable for Low Temperatures

An avalanche pulsing circuit, constructed with off the shelf components operates reliably at 4.2 K. Nanosecond pulses with amperes of peak current are delivered to low impedance loads. Physical proximity of generator and load eliminate cross talk and transmission line distortion.

Biasing Circuitry for Tunnel Junctions

A method of generating bias has been developed which greatly facilitates studying the voltage-current characteristics of tunnel junctions. A triangle wave to sweep the bias, a dc level for offset, and a small amplitude sine wave used for taking derivatives are all summed in a dc amplifier. The junction is biased by the attenuated output of this amplifier with either a high or low impedance load line. The two transistor circuits which largely comprise this bias supply are compact and battery powered, minimizing grounding problems.

Programmable Current Regulator for High-Voltage Operation

A current regulator for the operation of gas discharges is described, capable of delivering peak currents up to 1 ampere and average currents of up to 0.5 ampere with voltage excursions to 9 kV. Completely floating two-terminal operation accomodates different load configurations. By means of externally supplied timing pulses the output current can be programmed to generate rectangular or trapezoidal current waveforms. For rectangular output pulses, switching speeds of 5 μs into low-impedance loads and slewing rates of 500 V/μs for high-impedance loads can be obtained. The output resistance is in excess of 107 ohms, shunted by 50-250 pF, depending on regulator configuration.

An Analysis of Signal Pulse from Semiconductor Junction Detectors

An elementary method of wave form analysis for semiconductor detectors under certain working conditions is derived from a simple model of pulse formation. Agreement of the calculation with the corresponding experimental results is satisfactory. The experiments were carried out on an M-8811-A-50 detector (TOSHIBA, 2,500 Ω cm, p-type Si). The load resistance was in the range 100~50,000 Ω. The amplitude and the rise-time have been found to be in the ranges 1~6 mV and 3~9 ns, respectively. The energy spectrum of detector pulse for low load impedance extends up to ca. 50 Mc.

An Analysis of Signal Pulse from Semiconductor Junction Detectors

An elementary method of wave form analysis for semiconductor detectors under certain working conditions is derived from a simple model of pulse formation. Agreement of the calculation with the corresponding experimental results is satisfactory. The experiments were carried out on an M-8811-A-50 detector (TOSHIBA, 2,500 Ω cm, p-type Si). The load resistance was in the range 100~50,000 Ω. The amplitude and the rise-time have been found to be in the ranges 1~6 mV and 3~9 ns, respectively. The energy spectrum of detector pulse for low load impedance extends up to ca. 50 Mc.

Megampere Pulse Transformer for Coaxial Load

A transformer is described which delivers 2 MA into a low impedance load through a coaxial output line of about 6.35 mm inner conductor diameter and 12.7 mm cavity diameter. The transformer primary is connected to a 20 μF, 50 kV capacitor bank by forty-eight flexible coaxial cables. The ringing frequency of the system with the secondary shorted is 70 kc.

On Some Three-Terminal Lumped and Distributed RC Null Networks

The selectivity characteristics of some three-terminal lumped and distributed RC null networks are examined. The lumped networks considered are the bridged and shunted ladders. In the symmetrical configuration, both networks are found to be less selective than the corresponding parallel-T. By tapering the ladder portion and increasing the number of sections, they can be made as selective as, or even more selective than the asymmetric parallel- T. The distributed networks are obtained as logical extensions of the lumped ones and are studied for exponential, proportional and parabolic types of tapering. Proportional tapering is found to offer no advantage over the untapered-line network. The other two types yield better selectivity; the maximum selectivity with parabolic taper is, however, less than that obtained with exponential taper. For both lumped and distributed networks, the selectivity is found to depend upon the direction of taper. For low source and high load impedances, a higher selectivity is obtained if the impedance level increases with distance from the source, while for high source and low load impedances, the reverse case yields a higher selectivity.

Wide-Band Pulse Transformers for Matching Low Impedance Loads

Pulse transformers capable of matching the low impedance load characteristics of integrated circuits are discussed. Experimental models constructed by winding transmission lines on cores were found to pass pulses with rise times between 1 and 2 nsec and with little droop for pulses of 300-nsec width. A transformer in liquid helium transmitted a 1-μsec pulse with less than 10% droop.

Analysis of Signal Transmission in Ultra High Speed Transistorized Digital Computers

The transmission of digital signals plays an important role in high speed computers, not only because the traveling time on the connecting wire is a significant portion of the total delay, but also because the wire is a distributed parameter coupling network which, as a transmission line, becomes an integral part of the computer circuitry and affects the over-all performance. The classical theories of transmission lines are applied to study the signal waveforms. In the case of low input impedance loads, the radial (or parallel) transmission line scheme should be used. A mathematic relationship can be derived among the ramp slope of signals, the input current to the loads, the length and the impedance of the lines, and the terminations. Then the reflections can be predicted. Guided by this, one chooses the optimum line impedance, the maximum length and the proper termination. For high input impedance loads, the tapped transmission line scheme can be used. The multiple junction reflections are expressed in terms of a series which can be worked out by hand or by machine computation. Likewise, there is a relationship among the impedance of the tapped lines and the feeding line, the spacing of loads and the terminations. There are rules to be followed to decide the transmission scheme.