Showing papers on "Cascade amplifier published in 1990"

Modulation device with input signal modification for correction of amplifier nonlinearities

Abstract: In a modulation system using an amplitude and a phase of a carrier wave as information such as a QPSK system, a modulation device modifies an input signal series to compensate the nonlinear characteristics of an amplifier located at a later stage, and provides a carrier wave modulated by the modified signal series to the amplifier. A first arithmetic circuit obtains an amplitude and a phase of an input signal by calculation. A ROM is set with correction data corresponding to the calculated amplitude so as to compensate the nonlinearity of the amplifier. A modification value generating circuit and a RAM output an amount of compensation so as to further modify the correction data according to part of an output signal from the amplifier to compensate amplifier characteristic changes due to temperature variations and the like. A second arithmetic circuit provides a signal series produced from the modified amplitude and phase to a quadrature modulator.

A high efficiency uhf linear power amplifier

Abstract: An RF amplifier for a phase and envelope varying signal employs a class C operated device (110) for high efficiency. In order to improve the linearity of the class C operated device (110), a signal (s₂(t)) corresponding to the envelope of the amplifier output is formed and a portion thereof is fedback to an envelope modulation element such as a pulse width modulator (140) connected to the class C operated device (110) to reduce distortion at the amplifier output.

Error amplifier for use with parallel operated autonomous current or voltage regulators using transconductance type power amplifiers

Abstract: An error amplifier is disclosed for use in linear or switched-mode voltage or current regulators that use a transconductance type power-amplifier (32a, b, c), enabling easy modular parallel connection of said regulators by simply parallel wiring of normally externally accessible nodes of the individual regulators: power-input, power-output, error amplifier output (58), and error amplifier input (56), to boost the system's total output power by about equally sharing the total output power among the individual regulators, comprising of a. an amplifier with grossly asymmetric output current capability in sink and source directions; and b. a sense circuit to slightly modify the voltage on the reference input of the said amplifier when the lower value output current limit becomes active so that it causes positive feedback thereby ensuring that at any time only one of the plurality of parallel operated amplifiers is active and controls the system's output while all the other amplifiers are in current limit and thereby inactive.

Stored program controlled module amplifier bias and amplitude/phase compensation apparatus

Abstract: A stored program amplifier compensation apparatus utilizing sensing elements to provide the operational states of an RF power amplifier to a controller processor unit which utilizes the operational data to provide a bias control signal to the RF power amplifier. Look-up tables which are stored in the controlled processor unit, contain a bias control signal for all the possible operational combinations.

Amplifying with directly coupled, cascaded amplifiers

Abstract: A signal is amplified with a plurality of amplifiers (12-18), each amplifier having a reference port (22), a reference node (C) coupled to the reference port, and a signal port (22), and each amplifier being supplied by a power source (30-36) with operating potential with respect to the reference node that is coupled to the reference port of that amplifier. The amplifiers (12-18) are cascaded in a manner selected so that the output of a first amplifier (12) (which receives the signal to be amplified at its input port) drives the reference node (22) of a second amplifier (14), and the reference node (22) of the first amplifier (12) provides an input at the signal port (20) of the second amplifier (14), whereby the first and second amplifiers are directly coupled together to amplify the applied signal.

Amplifier having feed forward cancellation

Abstract: The present invention provides an amplifier arrangement to which feed forward correction is applied by a comparison loop including comparison means for comparing amplifier input with amplifier output to provide an error signal, a cancellation loop including secondary amplifier means for amplifying the error signal and combining means for combining said amplified signal with said amplifier output, a pilot generator coupled to said amplifier input to introduce a pilot tone therein, detector means for detecting a level of pilot tone in said amplifier output and correction means for correcting said cancellation loop performance as a function of said detection wherein said pilot generator is further coupled to a multiplier receiving said amplifier output, said multiplier producing an output signal arranged to control a loop parameter to effect said correction. The distortion performance of a feed forward amplifier is thereby improved, alternatively an amplifier of inferior distortion performance, but potentially higher efficiency may be used.

Multistage cascode radio frequency amplifier

Abstract: A cascode radio frequency amplifier in which a control amplifier stage is provided and any number of clone amplifier stages are connected in series (cascode) with the control amplifier. The cascode amplifiers provide equal voltage and power since each of the clone stages provides unity gain. The device can operate from low frequencies to high frequencies.

Feed-forward amplifier having increased compression point

Abstract: In order to improve the distortion performance of a feed forward corrected amplifier, an amplifier arrangement includes a distortion generator (312) which is coupled between an input (15) and a main amplifier (1). The amplifier arrangement is such that the input signal passes to the distortion generator (312) via a coupler (307). The signal passes via a delay network (310) which compensates for the delay of the distortion generator (312) and is tapped by a coupler (308) to be combined by a coupler (313) with the distorted signal from the distortion generator (312). In this way the output of the distortion generator is subtracted from a sample of the input signal so that only the distortion remains to pass via phase (314) and amplitude (315) correction networks to be amplifier by a gain element (316) before being coupled back into the main signal path by a coupler (309). The correction is active over a portion of the main amplifier characteristics such as the compression region of the main amplifier. Hence the main amplifier (1) compression point may be raised. Raising the compression point increases the overall power handling capability of the main amplifier by increasing the level at which the overall arrangement will saturate to cause distortion.

A graphic design method for matched low-noise amplifiers

Abstract: A graphic design method for matched low-noise amplifiers is presented in which all necessary design information is given in the load plane. It is possible to work exclusively in the load plane, as the input-matching requirement makes the source admittance dependent on the load admittance. As a consequence of the bilinear transformation involved, all parameters may be presented by circles. Analytic equations giving the centers and the radii of the circles in the load plane are presented. Two kinds of amplifier configurations are considered: a single-stage amplifier with an input-match requirement and a two-stage cascade amplifier. The latter is required to have an output match and noise-optimized second stage, in addition to an input match. For the single-stage case the noise figure, the power gain, the stability, and the input network are treated. In the cascade design, the total noise figure, the interstage network, and the available gain are treated as well. A design example for the case of lossless feedback is presented. >

Splatter controlled amplifier

Abstract: An amplifier circuit uses a microprocessor to count occurrences of the output stage going into saturation to decide when to control input levels to the amplifier. When the output amplifier stage saturates too frequently, the microprocessor controls a scaling line that effectively attenuates input levels to the amplifier, eliminating saturation levels. When the output stage saturates too infrequently, input levels to the amplifier are increased.

Linearized saturation amplifier with bidirectional control (LSA-BC) for digital mobile radio

Abstract: The design and performance of the LSA-BC, a novel power amplifier, are presented. A linear amplifier with the high efficiency of a switching-mode saturation amplifier can be realized. A high-efficiency GaAs FET is roughly linearized by dynamically varying its drain DC voltage with a high-efficiency variable-output DC-DC converter. A negative envelope feedback is utilized to compensate for the residual. The circuit construction is simple enough for use in the portable subscriber units of a digital mobile radio system. A 1.5-GHz-band 1-W LSA-BC was constructed to determine its performance with 32-kb/s roll-off QPSK (quadrature phase-shift keying). As a result, a 40% total efficiency is achieved as well as a stable third-order intermodulation distortion of -50 dB to the signal level. >

Symmetric bi-directional amplifier

Abstract: A transceiver module includes a bi-directional amplifier having a pair of symmetric signal paths for amplification of both transmit and receive signals is described. The amplifier is a bi-directional amplifier and includes a pair of symmetric signal paths. The amplifier is disposed between a pair of r.f. switches to provide a pair of signal paths between two terminals of the module. A phase shifter is coupled between one of the terminals of the module and one of the r.f. switches, wherein the second terminal of the module is coupled directly to the other one of the pair of switches.

Gradient amplifier system with flexible amplifier allocation

Abstract: A magnetic resonance imaging system uses a pool of amplifiers to generate gradient signals. Each amplifier within the pool may be switched among any of the gradient axes, so as to efficiently allocate amplifier power among the gradients. In one embodiment, the amplifiers of the pools are connected in stacks by an input and output matrix comprised of mechanical switches driven in tandem by interlocked motors. The switches connect the outputs of the amplifiers in series. The input signal is "boot strapped" through the amplifier stack to provide proper signal level.

Universal magneto-operational amplifier (MOP)

Abstract: A new class of integrated magnetic sensors, a magneto-operational amplifier (MOP) is presented. The MOP is a universal magnetic sensor which can be used for many purposes. The principle of the MOP is a feedback amplifier similar to the usual operational amplifier which is widely used for realizing any analog function. In order to make use of the advantages of an operational amplifier, the MOP has similar components: a differential amplifier stage which includes a magnetic detector; a sufficiently large gain amplifier; and an output stage. By changing external feedback elements, the MOP can realize various magnetic operations, such as a linear magnetic sensor, a magnetic switch, a magnetic filter, etc. In this paper experimental results of some applications of the MOP are given.

Offset-voltage-balancing operational amplifier

Abstract: An offset-voltage-balancing operation amplifier for difference signals includes an auxiliary and a main amplifier, each having a difference input and an auto-zero input. To provide offset balancing, the auto-zero inputs are connected to the potentials of two integrated storage capacitors. The difference input of the auxiliary amplifier can be short-circuited via first and second switching means, and the two storage capacitors are connected to the output of the auxiliary amplifier via third and fourth switching means. The sensitivity of the auto-zero inputs is less than the sensitivity of the difference inputs.

Distributed combiner power amplifier and method

Abstract: An improved distributed amplifier usable, for example, in the gigahertz frequency range for radar and electronic warfare applications is disclosed. In the amplifier stage a combination of optimum amplifier stage loading, a reflection cancelling output network, and an amplifier capacitance hiding input arrangement are employed. The disclosure includes specific component values for one embodiment of the invention.

Feed-forward amplifier including phase correction

Abstract: A feed-forward amplifier utilizes frequency dependent delay elements to cancel the effects of phase dispersion in the amplifier to amplify a broadband, high-frequency signal with low distortion.

Potential of the distributed amplifier as a photo-diode detector amplifier in high bit rate optical communication systems

Abstract: The theoretical performance of the common source MESFET amplifier and distributed amplifier as a post photodetector amplifier for use in high bit rate optical communication systems are compared. The calculations suggest that a 7dB improvement in the noise level may be obtained from the distributed amplifier in this situation in comparison with the conventional common source amplifier.

Improvements in or relating to amplifiers

Abstract: The present invention provides an amplifier arrangement to which feed forward correction is applied by a comparison loop including comparison means (16) for comparing amplifier input with amplifier output to provide an error signal, a cancellation loop including secondary amplifier means (101) for amplifying the error signal and combining means for combining said amplified signal with said amplifier output (102), a pilot generator (105) coupled to said amplifier input to introduce a pilot tone therein, detector means (109) for detecting a level of pilot tone in said amplifier output and corrections means for correcting said cancellation loop performance as a function of said detection wherein said pilot generator is further coupled to a multiplier (107) receiving said amplifier output, said multiplier producing an output signal arranged to control a loop parameter to effect said correction. The distortion performance of a feed forward amplifier is thereby improved, alternatively an amplifier of inferior distortion performance, but potentially higher efficiency may be used.

Micro-power gain lattice

Abstract: A broadband, high-gain RF signal amplifier which consumes a minimal amount of DC power has an input terminal to which an input signal to be amplified is coupled, and an output terminal from which an amplified output signal is derived. The signal amplifier has a plurality of first through n th signal amplification stages coupled in cascade between the input terminal and the output terminal. Each stage comprises an amplifier device having an input electrode, an output electrode and a control electrode. The output electrode is coupled to an amplifier device of an i th stage that is resistively coupled to the input electrode of the amplifier device of an (i+1) th stage, and is DC coupled through a rectifier device to the control electrode of the amplifier device of the (i+1) th stage. The control electrode of the amplifier device of the i th stage is resistively coupled to the input electrode of the amplifier device of the (i+1) th stage. The input terminal is coupled to the input electrode of the amplifier device of the first amplification stage, while the output terminal is coupled to the input electrode of the amplifier device of the n th amplification stage.

Logarithmic amplifier with sequentially limiting amplifier stages

Abstract: In order to improve the large signal handling capability of a logarithmic amplifier comprising amplifier stages successively performing their limiting actions in response to an increase of the input signal, and an adder stage for the output signals of the amplifier stages, the signal of the amplifier stage which is the last to perform its limiting action in response to an increase of the signal is amplified by a value which is higher than that of the signals of the other amplifier stages.

Point-to-multipoint distributions of 42 channel VSB-AM video signals using an erbium-doped fiber amplifier

Abstract: It is demonstrated that an erbium-doped fiber amplifier (EDFA) can be successfully used as a power amplifier for point-to-multipoint distributions of 42-channel VSB-AM video signals. The amplifier has a 31.4-dB net small-signal gain and 6.1-dBm saturated power. When used as a power amplifier, the EDFA is heavily saturated with a 19.2-dB gain compression and 12.2-dBm output power. The total optical power budget is 20 dB at CNR of 50 dB. Both composite-triple-bit and composite-second-order distortions after the amplifier and splitter are about or above 60 dBc. The possibility of cascading these fiber amplifiers and branching their outputs makes them well suited for tree-and-branch-like CATV distribution systems. >

2-stage differential amplifier connected in cascade

Abstract: A two-stage differential amplifier connected in cascade according to the present invention is suitable for fabrication within an integrated circuit, in which a constant current source circuit is connected with the common emitters of the transistors in the preceding stage differential amplifier, and the emitters of the transistors in the succeeding stage differential amplifier are connected with the collectors of these transistors through impedance elements. Current consumption in the overall amplifier is reduced and heat production therein is suppressed. Furthermore, since a capacitor is connected between the collector of each of the transistors in the preceding stage differential amplifier and the base of each of the transistors in the succeeding stage differential amplifier, it is possible to match easily the input and the output impedances in the succeeding and preceding amplifier by means of this capacitor and the impedance elements described above.

Output waveform control circuit

Abstract: An output waveform control circuit for a time division multiple access system (TDMA), including a second driving circuit which sends a control signal to the power amplifier in accordance with a signal outputted by the comparator circuit. Thus, by controlling the operating voltage of the power amplifier simultaneously with the control of the level input signal from the input level control circuit, the output characteristic of the power amplifier, including a class C or the like amplifier having a non-linear input/output characteristic, is prevented from varying abruptly, and the output waveform of the power amplifier is so controlled as to have gently sloped leading and trailing edges.

Optical control of a microwave switch

Abstract: An optical controlled attenuator circuit for controlling a microwave varie attenuator. The optical controlled attenuator circuit includes, a light source, a control connected to the light source, an optic fiber having an end coupled to the light source, a field effect transistor coupled to a second end of the optic fiber, a first inverting amplifier coupled to the field effect transistor, a second non-inverting amplifier coupled to the first amplifier means, a third non-inverting amplifier coupled to the second amplifier, a fourth inverting amplifier means also coupled to the second amplifier, and a microwave variable attenuator having first and second inputs respectively coupled to the fourth inverting amplifier and to the third non-inverting amplifier means and having an RF input and an RF output.

Amplifier arrangement with time constant control

Abstract: An amplifier arrangement suitable for use in a receiver for use in a telecommunications system is described. The arrangement includes an amplifier and an FET switch arrangement arranged to alter the time constant of the amplifier in dependence upon the incident signal frequency. A balance switch arrangement is arranged such that switching transients of the switch arrangement are cancelled out in the amplifier arrangement.

Linearization of amplitude response and phase correction for amplifier

Abstract: A high frequency amplifier circuit comprises an amplitude characteristic correction circuit and a phase characteristic correction circuit for compensating the non-linearity of the input-output characteristics of the amplifier. The amplitude characteristic correction circuit varies the drain voltage or the collector voltage of the amplifier in accordance with the envelope level of an input signal in such a manner that the relationship between the amplitude of the output of the amplifier and the amplitude of the input signal has linearity. On the other hand, the phase characteristic correction circuit provides a quantity of phase shift to the input signal in accordance with the envelope level of the input signal, and the phase-shifted input signal is applied to the amplifier in such a manner that the phase of the output of the amplifier and that of the input signal coincide with each other.

High gain semiconductor laser amplifier package

Abstract: A laser amplifier package comprises two laser amplifiers (1 and 2) coupled via two lenses (5 and 6) and an optical isolator 7. The first and second laser amplifiers may both be run as amplifiers to give an overall improved gain and reduced residual facet reflectivity. The first amplifier may be run as a pulse source as part of an LEC or gain switched DFB laser assembly. Pulses generated to be, or compressed to, near transform limited enable the output from the package to be optical solitons. The second laser amplifier may be switched to provide modulation.

An MMIC amplifier for automatic level control applications

Abstract: An automatic gain control amplifier for automatically leveled output power, broadband, swept-frequency applications to 3 GHz has been developed. Consisting of a variable- pi attenuator, four additive-gain amplifier stages, a temperature-compensated peak detector, and an output buffer, the amplifier features a maximum leveled gain of 22 dB, a gain control range of 25 dB good input and output matches to 50 Omega , and suppressed second-harmonic distortion. It operates with +or-6-V power supplies and dissipates approximately 800 mW. >