Showing papers on "RF power amplifier published in 1972"

Short-wave therapy apparatus

Abstract: A short wave therapy apparatus has two treatment heads enabling an operator to treat two separate areas of a patient at one time or to treat two patients simultaneously. The circuit includes a crystal oscillator, a pulse modulator, an RF buffer, an RF power amplifier and a ''''pi'''' network which precedes the interconnection with the attaching cables and the treatment heads. Each one of the cables is specifically selected in length so that it will be approximately a quarter wave electrical length thereby fixed tuning each one of the heads, varied only in 1/2 wave electrical lengths. An RF sample is picked off of the output from the RF power amplifier through a capacitive divider. The RF sample is fed back through a peak rectifier to a summing point where it is compared with the voltage on a pulse amplitude reference step switch and is delivered to a pulse amplitude control circuit. Further, a pulse generator and pulse rate control circuits are connected to the pulse modulator for control purposes. Accordingly, the correct power amplitude is maintained regardless of the loading on the particular heads. An oscilloscope is connected to the capacitive divider for the purpose of monitoring the operation of the apparatus.

Rf sputtering apparatus and method

Abstract: An RF bias sputtering apparatus is provided having simple on-off operation in which there is no detuning of the apparatus to an RF power source when sputtering conditions within the ionization chamber change. The capacitive reactances within the chamber and without the chamber are divided into a reactance bridge network, a capacitive reactance means being disposed across an arm of the bridge for balancing the reactances of the bridge network. Critical tuning requirements are reduced by the use of an RF power source with wide bandwidth tuning capabilities.

rf augmentation in CO2 closed‐cycle dc electric‐discharge convection lasers

Abstract: dc electrical power deposition in CO2 closed‐cycle electric‐discharge convection lasers (EDCL) can be increased to levels characteristic of open‐cycle performance by the application of rf (13.7‐MHz) auxiliary power. Experiments have been conducted with the radio frequency capacitively coupled into the discharge zone transverse to the dc field through the top and bottom walls of a rectangular laser channel. The effect of rf power on the dc power level and on the small‐signal gain coefficient is described.

High power bridge audio amplifier

Abstract: A high power audio amplifier includes four power amplifier sections connected in a bridge, with the power supply connected to one opposite pair of nodes and the load terminals connected to a second opposite pair of nodes One of the load terminals may be connected to a ground reference potential and the power supply is floating with reference to ground First and second drive amplifiers are provided, with each of the drive amplifiers being connected to the two power amplifier sections connected to one load terminal The input signal to be amplified is applied to one input of the first drive amplifier and a feedback signal from the load terminal which is not connected to ground is connected to the second input thereof The second drive amplifier receives either the input signal or the signal from the load terminal, and compares the same with the supply potential to balance the bridge To protect the transistors of the power amplifier sections, the currents in the transistors of the amplifier sections driven by the second drive amplifier are sensed and used to control the first drive amplifier, to thereby protect the transistors in all of the power amplifier sections Auxiliary protection circuits are provided for the transistors in the power amplifier sections coupled to each drive amplifier

The Wide‐Band Driven RF System for the Berkeley 88‐Inch Cyclotron

Abstract: The wide‐band driven RF system, recently commissioned at the Berkeley 88‐Inch Cyclotron, offers a much needed lever on dee voltage stability at no sacrifice in rapid tuning flexibility, hopefully at a substantial reduction in tube replacement costs comparative to the original oscillator RF power source.

A 15-W monolithic power operational amplifier

Abstract: The design of a new general-purpose monolithic power amplifier functional block is described and the flexibility of the block in various applications is discussed. The effects of thermal coupling on the die between components in high-gain dc power amplifiers are examined and a technique is presented for the analytical evaluation of dc circuit performance in the presence of these thermal interactions. Experimental results from the 15-W amplifier are presented. A new integrated power transistor structure is described that includes emitter degeneration resistors as part of the emitter structure. Circuit performance is summarized.

An ENDOR Spectrometer Using a Slow Wave Resonance System

Abstract: An ENDOR spectrometer is described that uses a microwave helix instead of a resonant cavity. With this arrangement, the sample can be irradiated simultaneously with large rf fields (15 G; 10–40 MHz) using a low power rf amplifier (10 W) and a microwave field (X band). Measurements have been performed on organic radicals at room temperature.

Fm heterodyne transmitter

Abstract: An FM heterodyne transmitter is disclosed useful, for example, in a microwave relay link, using all solid-state components throughout. The transmitter includes an RF amplifier which generates locally a signal having the same frequency as the signal carrier and a phase comparator which accepts both the local and the received signals and provides an error signal responsive to a phase difference between them. The error signal is used in a feedback amplifier loop to correct the local oscillator frequency in the direction which tends to negate the error signal.

Emission of coherent microwave radiation from a relativistic electron beam propagating in a spatially modulated field.

Abstract: Intense electromagnetic radiation has been observed from the interaction of an intense relativistic electron beam and a spatially modulated magnetic field. An efficiency of conversion of electron kinetic energy into microwave radiation of the order of 1% has been achieved, with total rf power radiated greater than 30 MW. A parametric study has shown that the device has not reached saturation over the range of parameters tested. The experimental results show that the new device differs from conventional generators in several respects. For example, the frequency and the bandwidth of the rf radiation can be tuned over a wide range and the power at the harmonics of the fundamental frequency (∼ 1010 Hz) is the same order of magnitude as the power in the fundamental. Infrared radiation has also been observed; more than 1 MW has been found even for wavelengths under 10 μm.

Computer controlled rf noise and modulation analyzer

Abstract: A computer controlled test set capable of measuring FM and AM noise of an RF signal as well as the index of modulation, RF power level and the linearity of a ramped FM signal output from a microwave signal oscillator included in a unit under test.

1-2 GHz high-power linear transistor amplifier

Abstract: The development of an octave bandwidth, linear 1O-W amplifier using MIC techniques will be described. The amplifier consists of three hybrid-coupled balanced stages using ballasted transistors in special microstrip carriers.

Progress in the Efficiency of Free-Space Microwave Power Transmission*

Abstract: Recent developments in rectenna design and microwave beam launching have increased the ratio of the dc power output from the rectifier at the receiving point to the rf power input to the transmitting antenna from 0.41 to 0.60. The efficiency of microwave beam launching has been improved through the use of the dual-mode horn which has exceptionally low power loss in its side lobes. Improvement in the efficiency at the receiving point has resulted from increased capture efficiency of the rectenna.

Rf amplifier control system

Abstract: Two RF amplifiers may be selectively coupled and decoupled between a single antenna and a single mixer by switching circuits associated with each amplifier. A PIN diode is connected between the antenna and the input of each RF amplifier. A switching arrangement includes a complementary pair of transistors, one connected between a source of DC operating voltage and the amplifier and the other connected between the first transistor and the PIN diode. When the first transistor is biased to conduction by an appropriate control voltage, the associated RF amplifier is activated and DC current flows through both transistors causing the PIN diode to present a low impedance to RF signals from the antenna. When the first transistor is biased to cutoff by an appropriate control voltage, no current flows in the transistors inactivating the RF amplifier and causing the PIN diode to present a high impedance to RF signals from the antenna.

A C-Band All Ferrite Integrated Wideband High Power GaAs Avalanche Diode Amplifier

Abstract: A C-band 4-stage, 20 dB gain, 3-watt 25% bandwidth all ferrite substrate integrated GaAs avalanche diode amplifier is developed. The design procedure, as well as the amplifier performance including amplifier phase characteristics, is described. A power combining circuit which increases the output power capability by a factor of two is included in the output stage.

Integral rf modamp

Abstract: An RF modulator amplifier in a first feedback loop includes a comparator which produces an error signal whenever the audio input differs from a sampled portion of an AM modulated output. The error signal controls the current supply to the last RF amplifier stage. The voltage at the last RF amplifier stage is maintained constant by a second feedback loop which includes a voltage detector which senses this voltage to generate a second error signal which is used to set the drive of first and second RF amplifiers.

Amplifier with protective energy limiter circuit components

Abstract: A direct coupled state high fidelity amplifier incorporates an energy limiting circuit to provide protection against the user accidentally overloading and damaging the amplifier. The energy limiting circuit is designed so that the output transistors of the amplifier cannot be required to carry a specified amount of power for a longer period than would permit their safe operation without damage. This is done by examining and limiting the time integral of the product of voltage and current, i.e., energy, that the output transistors of the amplifier absorb. The result of using the energy limiting circuit is an increase in the efficiency of utilization of the output transistors, which in turn allows for an increase in power supplied by the amplifier to other components of the stereo system, while reducing the number of output transistors required.

Heterodyne amplifier circuits

Abstract: A nonlinear transmitter final RF amplifier is used as a mixer circuit to obtain the difference frequency between the transmitter RF frequency and a received offset frequency. The use of this circuit in radar altimeters is shown.

Stabilization of parallel transistor amplifiers

Abstract: An unstable two-transistor RF amplifier can be stabilized by a single resistive element that dissipates no RF power. Limitations of the technique are given, and the use of a complex stabilizing impedance is discussed for various conditions of instability.

High-power microwave amplifier using IMPATT diodes

Abstract: A single multichip IMPATT diode, operating in the unconditional amplifying mode, has been used as a reflection amplifier in the 6–8 GHz range. C.W. power-output levels of 4.0 W have been achieved with a stable reflection-amplifier circuit, using two multichip diodes in separate cavities coupled to a single circulator through an airstrip hybrid. The gain of the amplifier is 6 dB, with 250 MHz (−1 dB) bandwidth.

TRIUMF rf amplifier and resonator system.

Abstract: The TRIUMF RF system consists of a 23.1 MHz fixed frequency driven amplifier with a power capability of 1800 kW. Power is transmitted to the resonator system through a 50Ω water‐cooled line and is coupled to the system by a single coupling loop in one side of the push‐pull resonator system. The resonators are constructed of copper‐surfaced roll‐bond aluminum plates with integral cooling tubes. DC plate power for the four push‐pull 4CW250000A tetrode amplifiers is produced in a single unit rated at 20 kV, 130 A with crowbar protection for the tubes.

Rf microwave amplifier and carrier

Abstract: A power transistor and carrier advantageous for RF power (e.g. microwave) amplifier applications with improved linearity in class AB operation. The carrier comprises a channel-shaped member having a centrally located transistor mounting platform between two parallel rail members. One rail member includes a recessed plated portion for receiving base electrode wire bonds, and the other rail member includes a recessed portion including plating which is integrally contiguous with plating on the bottom surface of the carrier, whereby a resistive member may be mounted thereon with electrical contact to the bottom surface. The resistive member is low ohmage with high current capacity and is interconnected with the transistor emitter thereby insuring linear transistor operation by maintaining base-emitter junction forward bias, yet minimizes gain loss attendant with an emitter resistor.

Parallel transmission line matching network for connecting together a plurality of r.f. amplifier transistors

Abstract: A transmission line matching network for connecting a plurality of RF amplifier transistors together in parallel in a manner to assure substantially symmetrical division of power between the amplifier transistors includes a first plurality of similar transmission line matching networks each connected to one of the amplifier transistors to transform the impedance of each transistor to a predetermined level and a second transmission line matching network connected to each of the first matching networks for matching the impedances of the individual matching networks to that of another transmission line.

Power regulator circuit for a radio transmitter

Abstract: In a battery-powered radio transmitter, the radio frequency (rf) output power of amplifier and/or frequency multiplier stages is maintained more nearly constant, despite changes in battery voltage, by a regulator circuit. A feedback resistor is provided in the emitter-collector path of a transistor in a later stage to develop a direct current feedback voltage for the emittercollector path of the transistor of an earlier stage. This feedback voltage biases the earlier transistor so that as the battery voltage (and hence rf output power) decreases, the gain of the earlier stage is increased to maintain the rf output power more nearly constant.

Rf power transistor secondary breakdown protection circuit

Abstract: A protection circuit for RF power transistors to prevent secondary breakdown includes gate means to monitor both the collector current and collector voltage. A gate pulse generated each time the collector voltage exceeds a preset value is used to gate a wave form derived from the transistor collector current. When the current wave form is in phase with the gate pulse and is of sufficient amplitude, the gate means provides a controlled voltage to bias off the transistor power supply for purposes of reducing the output power to safe operating levels.

Modular solid-state power amplifier

Abstract: A modular solid-state amplifier capable of delivering several kilowatts of audio-frequency power over a frequency range of 0 to approximately 7,500 hertz and which has an output impedance selectively variable from substantially zero to approximately 100,000 ohms. The amplifier modules may readily be combined to obtain either voltage or current gain, or both, by appropriate series and parallel arrangements, or combinations thereof.

A monolithic differential-output operational amplifier

Abstract: A differential output operational amplifier using sealed-junction, beam-lead technology will be described. Innovative use of common-mode feedback facilitates the design of an amplifier with performance characteristics superior to those of its predecessors.

Gridistor: field-effect transistor for an ultra-high-frequency power amplifier

Abstract: The characteristics and performance of a 1 W, 1 GHz gridistor, an original field-effect silicon transistor with an embedded grid, has enabled us to achieve, in class A, a 1 W power output with a gain of 7 dB and a good linearity in output-power variation with input power, with a common-grid configuration.

Relaxing-avalanche-mode reflection amplifier

Abstract: This letter discusses a single-stage relaxing-avalanche-mode silicon p+-n-n+ reflection amplifier operating at 7.4 GHz with a small-signal gain and half-power bandwidth of 31. 5 dB and 20 MHz, respectively. A description of the amplifier and a discussion of its operation are given.