Showing papers on "Amplifier published in 1992"

Fiber Optic Networks

Abstract: Fibre optic networks applications and their requirements fibres, couplers and taps tunable filters laser diodes lightwave amplifiers modulation and remodulation techniques detection and demodulation of optical signals subcarrier (wavelength x frequency) techniques frequency stability and its control organizing the system topologically layered architectures in lightwave networks multiaccess, switching and performance operating third generation links operating third generation multipoints operating third generation networks

A 100-MHz 100-dB operational amplifier with multipath nested Miller compensation structure

Abstract: A multipath nested structure which overcomes the bandwidth reduction in the conventional nested structure by appending an independent feedforward path for high frequencies is presented. At low frequencies, the opamp behaves as a three-stage nested Miller-compensated amplifier, while at high frequencies the opamp has the nature and bandwidth of a two-stage amplifier with simple pole splitting. In this fashion, the concept circumvents the classical DC-gain/high-frequency-performance dilemma. No pole-zero doubles occur, because the two regions of operation can be independently and closely matched, unaffected by variations in the parameters of the IC process in which the amplifier is fabricated. >

High efficiency bi-directional spatial power combiner amplifier

Abstract: The present invention is a high efficiency bi-directional spatial power combiner for extremely high frequency signals. In one embodiment, orthogonally polarized electro-magnetic waves are used to isolate signals going into and out of a planar array of amplifiers. A dual mode horn transmits vertically polarized fields to a MMIC planar array of amplifiers. Vertically polarized array elements receive the signals, amplify them, and retransmit back to the horn using horizontally polarized array elements. An ortho-mode transducer on the horn provides isolation for the two polarized signals. The backside of the array can be used for a heat sink, and to provide access for DC biasing of the array elements. In a second embodiment, monolithic grid oscillators are used in lieu of power amplifiers with orthogonal polarization array elements. The input signal and the output signal are of the same polarization. A circulator is used in lieu of an ortho-mode transducer to isolate the input signal from the output signal.

Ultra-high speed modulation-doped field-effect transistors: a tutorial review

Abstract: A tutorial review on the modulation-doped field-effect transistor (MODFET) and its application to ultra-low-noise, medium-power, and ultra-wide-band traveling-wave amplifiers as well as ultra-high-speed digital logic circuits is presented. It is believed that with further advances in material growth and device scaling significant improvements in cutoff frequencies, switching speed, noise, and power will be achieved in the near future. >

Dual mode transmitter and receiver

Abstract: A dual-mode transmitter having an antenna (109), a mode controller (103), a source encoder, a tunable-frequency synthesizer (105), a chip-code generator (107), a spread-spectrum modulator (111), a narrowband modulator (113), a power amplifier (115), and an adjustable bandpass filter (117). Also provided is a dual-mode receiver having a mode controller (103), a tunable-frequency synthesizer (105), a chip-code generator (107), an antenna (109), an adjustable bandpass filter (117), a preamplifier (205), a frequency converter (209), an IF amplifier (211), a spread-spectrum despreader (215), a spread-spectrum demodulator (217), a narrowband modulator (213), and a source decoder. For the transmitter and receiver, the mode controller (103) selects receiving a narrowband modulation or a spread-spectrum modulation. The tunable-frequency synthesizer (105) generates a local oscillator signal for the receiver, and a carrier signal for the transmitter. The chip-code generator (107) generates a chip code signal for both the transmitter and the receiver. With a narrowband modulation setting of the mode controller (103), the transmitter and receiver have the adjustable bandpass filters (117) adjusted to a narrowband width for telephone communications. With a spread-spectrum setting of the mode controller, the adjustable bandpass filters (117) and the system are adjusted to transmit and receive a wide bandwidth for passing the spread-spectrum signal.

Output stage for current-mode feedback amplifiers, theory and applications

Abstract: A novel building block is described, termed FCS (floating current source), which may serve as class A output stage for CFAs (current-mode feedback amplifiers). It is capable of driving a grounded load with a bipolar signal, and yields a feedback current equal to the output current over a wide frequency range. Its possible range of application covers MOSFET amplifiers employed in analog signal processing and current-operated control systems. An internal interconnection converts the FCS into a CCII-. Another novel CCII- configuration employs a push-pull folded cascode and may serve as noninverting input stage for a standard amplifier configuration. Finally, a feedback-stabilized CCII- and a CFA are described, both employing the FCS as output stage.

Optical transmission system equalizer

Abstract: Increasing the capacity of an existing lightwave transmission system can be accomplished by either increasing the bit rate or adding wavelength-multiplexed channels Recent advances in erbium-doped fiber amplifier technology make the wavelength division multiplexed option particularly attractive Unfortunately, because of nonuniform wavelength-dependent gain profile and saturation characteristic of erbium-doped fiber amplifiers, each channel of a wavelength-multiplexed system will experience a different optical gain which, in turn, can result in an excessive bit-error-rate performance in some channels This invention is directed toward processing apparatus which selectively equalizes the optical gain or the optical signal-to-noise ratios of the channels of a wavelength-multiplexed optical transmission system The output powers and the signal-to-noise ratios are selectively equalized by adjusting the optical input signal powers With this invention, wavelength-multiplexed channels can be added to an existing optical fiber transmission system without requiring new optical components, upgrades or adjustments at intermediate amplifier sites

Current-mode continuous-time filters: two design approaches

Abstract: Two different ways to implement current-mode analog signal filtering are proposed. A practical comparison of filter structures using an approach involving operational transconductance amplifiers and current replica circuits is presented. Experimental results for a bandpass filter using the current mirror approach are presented and discussed. >

High frequency power amplifier

Abstract: In a base-bias-control-type high-frequency power amplifier with a plural stage configuration, a rising voltage of a base bias current supplied to an initial stage transistor is made lower than a rising voltage of a base bias current supplied to a second stage transistor by a bias circuit, and a difference between the both voltages is set to be smaller than a base-emitter voltage of an amplifying stage transistor. Also, a rising voltage of a base bias current supplied to a third stage transistor is made equal to the rising voltage of the base bias current supplied to an initial stage transistor. Accordingly, a technology capable of improving the power control linearity can be provided in a high-frequency power amplifier used in a polar-loop transmitter or the like.

Femtosecond pulse amplification at 250 kHz with a Ti:sapphire regenerative amplifier and application to continuum generation

Abstract: Ultrashort optical pulses have been amplified to 1.7 μJ of energy at a repetition rate of 250 kHz with a novel cw argon-pumped Ti:sapphire regenerative amplifier. Acousto-optic switching of the amplifier is used to achieve the high repetition rate. Chirped-pulse amplification is used to avoid nonlinear effects in the amplifier. After recompression, 1-μJ, 130-fs pulses are obtained and are used to generate a white-light continuum in an ethylene glycol jet.

An adaptive predistorter for a power amplifier based on adjacent channel emissions (mobile communications)

Abstract: A slowly adapting predistorter is presented. The approach is to minimize the transmitter output power in spectral regions occupied only by intermodulation (IM) products. In this way, only a spot power measurement is required. This technique relies on the principle that the power amplifier's characteristics vary slowly with time. By monitoring the out-of-band power one can obtain an estimate for the distortion introduced by the power amplifier. Adaptation is accomplished by iterative adjustment of the predistorter parameters to minimize the IM power. For a polynomial predistorter, the authors analytically demonstrate that the IM power is a quadratic function of the coefficients. A variety of algorithms therefore apply. The authors present an analog static predistortion linearization circuit that uses the envelope of the baseband signal to generate the nonlinear functional used in predistorting the input signal. The improvement obtained with an amplitude-modulated input signal was 15 dB in the third- and 5 dB in the fifth-order intermodulation products. The IM improvement could be maintained with the use of a robust direct search algorithm. >

High-power strained-layer InGaAs/AlGaAs tapered traveling wave amplifier

Abstract: High power, nearly diffraction‐limited cw performance has been obtained from a traveling wave amplifier, fabricated in a strained‐layer InGaAs/AlGaAs laser structure, with a laterally tapered gain region and with a cavity‐spoiling feature to prevent laser oscillation. The input beam diffracts as it propagates, efficiently filling the tapered active region. For input optical power of 85 mW from a Ti:sapphire laser, total cw output of 1.44 W has been achieved with 1.28 W in a central lobe with width less than 1.2 times the diffraction limit at 977 nm wavelength. Only 15 mW of power incident on the amplifier was sufficient to provide 1 W output into the central lobe.

Control system for calibrating and driving ultrasonic transducer

Abstract: An electronic control system for determining the resonant frequency of and driving ultrasonic transducers in a phacoemulsification probe used for ophthalmic surgery. The control system includes a voltage control led oscillator, power amplifier, power monitor, and automatic gain control circuit operating under the direction of command signals received from a microprocessor-based control console. The control system operates in a constant apparent power, direct drive mode with closed loop feedback maintaining the electrical power provided to the primary of a RLC transformer at the constant level requested by the command signals from the console. The frequency of the drive signal is held at the dominant resonant frequency of the ultrasonic transducer which is being driven by the control system. This resonant frequency is determined via a calibration procedure performed when the probe is first attached to the control system. During this procedure a constant voltage drive signal is swept through a range of frequencies and the electrical power consumed by the transducer is measured and stored at selected intervals such as 100 Hertz increments. The resonant frequency is also determined in part by looking for the frequency at which maximum power is consumed by the probe. The stored data is also subjected to other tests to check that the peak is indeed a resonant frequency and that the probe has selected output power characteristics about this resonant frequency, thus helping to ensure that the probe is capable of operating satisfactorily when driven by the control system.

Experimental performance of an adaptive digital linearized power amplifier (for cellular telephony)

Abstract: Amplification of linear modulation schemes, (which exhibit fluctuating envelopes), by high power amplifiers invariably leads to the generation of distortion and intermodulation products. Recent theoretical work has suggested that a complex gain predistorter may be employed to linearize a nonlinear power amplifier. The authors present experimental results demonstrating that a reduction in out-of-band spectra in excess of 20 dB may be achieved by employing digital feedback and a complex gain predistorter. >

Matrix array image sensor chip

Abstract: A matrix array image sensor integrated circuit chip is provided including horizontal and vertical scanning means with the sensor cells within columns of the array being associated with an analogue charge sense amplifier. The analogue charge sense amplifier includes a first amplifier in the form of an inverting charge integrator which provides a preliminary detection of the charge accumulated in the sensing cell by integrating the charge to produce a voltage which is capacitively stored in a voltage storage means. The sensing cell may then be reset by control logic while it is isolated from the stored voltage which is in turn selectively sampled using a switch to read out through a second amplifier stage to be provided as an output from the integrated circuit chip. A method for operation of the device in processing an image read cycle is also provided.

Detailed dynamic model for semiconductor optical amplifiers and their crosstalk and intermodulation distortion

Abstract: An advanced dynamic model for multisection semiconductor optical amplifiers is presented. It accounts for the carrier and field distributions in the longitudinal direction as well as for the facet reflectivities. The model can handle arbitrary time-varying input signals and current modulations. The model is used to assess intermodulation distortion and crosstalk. Cascaded amplifiers are considered, and the crosstalk and intermodulation distortion due to cascaded amplifiers are found to accumulate by adding together in amplitude; this may limit the number or cascaded amplifiers in multichannel systems. Carrier-induced nonlinearities depend strongly on facet reflectivities; for 25 dB of single-pass gain, a reflectivity of 5*10/sup -4/ will result in 3 dB excess distortion. Reduction of intermodulation distortion by use of multisection amplifiers is found to be possible only for small channel separations ( >

Power gain in feedback amplifiers, a classic revisited

Abstract: A tutorial review of a classic paper by Samuel J. Mason (1954) is described. That paper contained the first definition of a unilateral power gain for a linear two-port and the first proof that this grain is invariant with respect to linear lossless reciprocal four-port embeddings, thereby making it useful as a figure of merit intrinsic to the device. In this work, that original paper is brought up to date, a tutorial exposition of its contents is presented in a modern form, and its significance and applications in microwave engineering are discussed. The subsequent advances in the subject area are summarized, so that the original paper can be placed within a broader context and understood with a more general perspective. >

An analog implementation of discrete-time cellular neural networks

Abstract: An analog circuit structure for the realization of discrete-time cellular neural networks (DTCNNs) is introduced. The computation is done by a balanced clocked circuit based on the idea of conductance multipliers and operational transconductance amplifiers. The circuit is proposed for a one-neighborhood on a hexagonal grid, but can also be modified to larger neighborhoods and/or other grid topologies. A layout was designed for a standard CMOS process, and the corresponding HSPICE simulation results are given. A test chip containing 16 cells was fabricated, and measurements of the transfer characteristics are provided. The functional behavior is demonstrated for a simple example. >

Monolithically integrated 4×4 InGaAsP/InP laser amplifier gate switch arrays

Abstract: Monolithically integrated 4×4 semiconductor laser amplifier gate switch arrays comprising 24 integrated laser amplifiers have been fabricated and evaluated. Net positive optical gain between fibres, high extinction ratio, and low crosstalk are reported.

Operational transresistance amplifier using CMOS technology

Abstract: The Letter describes the design of a versatile analogue building block, termed an operational transresistance amplifer (OTRA). An operational transresistance amplifier has two low-input-impedance terminals and one low-output-impedance terminal. It is found to have a constant bandwidth indpendent of the gain in most closed-loop configurations. Simulation results are presented to demonstrate the constant-bandwidth performance. As an application example this amplifier is used to implement a MOSFET-C differentiator, of which analysis and simulation results are also presented.

Phase-mismatching characteristic of four-wave mixing in fiber lines with multistage optical amplifiers

Abstract: Fiber four-wave mixing in transmission lines with multistage optical amplifiers is studied. A theoretical model is described, and a fundamental experiment is carried out. It is shown that the phase-mismatching characteristic differs in transmission lines with and without amplifiers.

Experimental performance of an adaptive digital linearized power amplifier

Abstract: The authors present experimental results in which an adaptive complex gain predistorter achieved a reduction in out-of-band spectral emissions in excess of 20 dB for a class AB amplifier operating close to saturation. The experimental results demonstrate that a class AB power amplifier may be linearized without sacrificing efficiency. Although significant spectral reduction was achieved in the adjacent channel, the out-of-band spectral floor was flat and approximately -50 dB from the inband spectra. The complex gain predistorter exhibits two distinct advantages: a design engineer is not forced to back off a power amplifier to its linear but highly inefficient operating point; and adaptive correction allows the effects of frequency changes, drift in bias, operating point, aging and thermal stress to be readily compensated. >

CATV distribution networks using light wave transmission lines

Abstract: A communications network uses optical fibers to carry amplitude modulated broadband CATV signals over a considerable distance (6-30 km) to a fiber node. Electrical to optical transmitters at the headend launch, and optical to electrical receivers at the fiber node receive, optical signals corresponding to the broadband CATV signals. Distribution from the fiber node to the subscribers is obtained by transmitting electrical signals through a limited cascade of amplifiers over an electrical transmission line (coaxial cable). The limited cascade is much shorter than the fiber span and may include trunk amplifiers which are insufficient in number to add significant losses or distortion. Line extender amplifiers may be connected to output couplers located off the subscribers premises and the CATV signals then carried via electrical cables to the subscribers. In order to reduce harmonic distortion in the optical portion of the network, all or a portion of the CATV spectrum is translated to a frequency range which is less than an octave. One or more additional fibers are used for the channels in the upper portion of the band which need not be translated. The translated portion of the optical signals is received and translated back to its original frequency range and combined with the other band limited portions to provide a broadband signal for distribution to the subscribers.

Low noise operation of Er3+ doped silica fibre amplifier around 1.6 μm

Abstract: A novel method of using two pump wavelengths to achieve high gains and enhanced noise performance in the 1.6 μm Er3+ doped fibre amplifier is demonstrated. By launching 82 mW of power at 1.48 μm and up to 1 mW at 1.555 μm, a maximum gain of 31 dB is achieved at 1.57 μm with gains in excess of 24 dB available between 1.57 and 1.605 μm. The noise figure is maintained below 5dB over this bandwidth, close to the theoretical minimum for a 1.48 μm pumped amplifier.

Trigger circuit unit for operating light emitting members such as leds or motors for use in personal ornament or toy in synchronization with music

Abstract: A trigger circuit unit including: a forward circuit block having a pickup circuit such as a microphone for picking up a signal of music so as to convert it into an electric signal; a filter circuit for selecting a portion of the band from a picked up audible frequency band; and a limit amplifier circuit mainly composed of an inverter operation logic IC for amplifying the selected electric signal having a portion of the band and transmitting an output having a predetermined amplitude; and a waveform conversion circuit block having a time constant circuit connected to the output of the forward circuit block and composed of a capacitor having one or more diodes connected in series and a resistor in order to prevent a backflow and to obtain a forward directional voltage difference, wherein analog pulse signals transmitted from the time constant circuit are caused to perform a Schmidt operation having a previously adjusted degree of hysteresis, wherein the rectangular pulse signals transmitted from the waveform conversion circuit block in accordance with the electric signals which correspond to the music signals each having a partial band picked up, selected and amplified in the forward circuit block are transmitted as basic trigger signals for operating light emitting members such as LEDs or motors.

The deconvolution method of fast pulse shaping at hadron colliders

Abstract: We describe a new technique for front-end signal processing of signals from LHC or SSC detectors which precisely defines the origin of an event in time while maintaining amplitude measurement with an excellent signal to noise ratio. The method is designed for use with silicon detectors whose leakage currents may be substantially increased during the lifetime of an experiment by radiation damage, although it is likely to be applicable to other types of detector. It makes use of a shaping amplifier with a time constant of several beam crossing intervals and is particularlt well matched to CMOS front ends where low power consumption and low noise is best achieved by utilising pulse shapes with time constants ∼50 ns. It is based on discrete time filtering of data extracted from an analogue pipeline after a first level trigger. A finite impulse response type filter deconvolutes the sampled voltages of a shaped pulse to retrieve the original impulse signal with high precision. We describe the mathematical basis of the technique and its implications for timing and signal to noise. Measurements have been made on a CMOS amplifier intended as a prototype for readout of silicon microstrip detectors at LHC which demonstrates the power of this approach. A CMOS circuit emulating the filter is being built. It has been implemented with extremely low power consumption (

A unified analysis of MMIC power amplifier stability

Abstract: The author develops the mathematical framework and techniques for predicting possible oscillations for all n modes in order to ensure MMIC monolithic microwave integrated circuit stability. Although the analysis is applicable to any number of combined devices, only the cases for n=2 and 4 are discussed. These two cases illustrate the special considerations that apply for small numbers of combined devices (n=2) and the difficulties in analyzing larger numbers of combined devices (n=4). It was shown that the stability of the amplifier for all modes (even and odd) can be checked using small signal analysis software. >

Transceiver with rapid mode switching capability

Abstract: An RF transceiver achieves a fast switching time between transmit and receive modes by leaving the transmit oscillator (12) on all the time. The transmit chain comprises a wide pulling voltage controlled crystal oscillator (12) that operates at one third the transmit frequency followed by a frequency tripler/filter/amplifier chain that can be quickly switched on and off. By operating the transmit oscillator at one third the transmit frequency, only the third harmonic of the oscillator falls into the sensitive receive frequency band. Further isolation during the receive mode is achieved by gating off the frequency tripler, pulling the frequency of the oscillator out of the receive band, electronically detuning the harmonic filter (16) and switching off the transmitter's power amplifier (18).

Capacitively-coupled test probe

Abstract: The invention is a capacitively coupled probe which can be used for non-contact acquisition of both analog and digital signals. The probe includes a shielded probe tip, a probe body which is mechanically coupled to the probe tip, and an amplifier circuit disposed within the probe body. The amplifier circuit receives a capacitively sensed signal from the probe tip and produces an amplified signal in response thereto. The amplifier has a large bandwidth to accommodate high-frequency digital signals. Further, the amplifier has a very low input capacitance and a high input resistance to reduce signal attenuation and loading of the circuit being probed. The amplifier circuit is disposed in the probe body closely adjacent to the probe tip in order to reduce stray and distributed capacitances. A reconstruction circuit reconstructs digital signals from the amplified capacitively sensed signal.

A high-speed sensing scheme for 1T dynamic RAMs utilizing the clamped bit-line sense amplifier

Abstract: A clamped-bit-line sense amplifier (CBLSA) capable of very high-speed operation in one-transistor (1T) DRAM applications has been developed. Results from an experimental test chip demonstrate that the speed of the new circuit is insensitive to bit-line capacitance. Circuit speed is also found to be insensitive to the initial bit-line difference voltage. The CBLSA maintains a low impedance fixed potential on the bit lines during sensing, virtually eliminating sensitivity to inter-bit-line noise coupling and minimizing power supply bounce during sensing. The new sense amplifier operates at higher speeds than conventional circuits and still dissipates less power. >