Showing papers on "RF power amplifier published in 1981"

Maximum power control for a solar array connected to a load

Abstract: An analog and a digital control is provided which causes a dc to ac inverter operated in the constant power mode to supply sinusoidal current to a utility while drawing maximum power from a solar array. The current drawn from the array is forced to be proportional to the array voltage by a variable gain amplifier so that the inverter presents a resistive load to the array which remains statically stable under rapid changes of insolation while using a perturb-and-observe method of maximum power tracking. The perturb-and-observe method adjusts the gain of the variable gain amplifier to achieve maximum power output from the solar array.

Class E high-efficiency tuned power oscillator

Abstract: The class E high-efficiency transistor tuned power oscillator, based on the class E power amplifier, is presented. Theoretical conditions for optimum operation of the oscillator are formulated. A new feedback-loop circuit is proposed and a corresponding oscillator design procedure is given. Experimental results show that the collector-voltage and collector-current waveforms and the collector efficiency of the oscillator are the same as in the class E amplifier with the same transistor and operating at the same frequency. The measured collector efficiency was over 95 percent with 3 W output at 2 MHz. The proposed oscillator is especially applicable at high frequencies because it minimizes the power dissipated during the transistor off-to-on transition, even if the switching time is an appreciable fraction of the signal period.

Gain, frequency bandwidth, and saturation output power of AlGaAs DH laser amplifiers

Abstract: Signal gain, frequency bandwidth, and saturation output power, which are important parameters in determining preamplifier and linear repeater system performance, are studied theoretically and experimentally for AlGaAs Fabry-Perot cavity type laser amplifiers. Multimode rate equations with an input signal term are solved for the exponential bandtail model with no k -selection rule. Experimental results are in reasonable agreement with theoretical predictions. The maximum signal gain, frequency bandwidth, and the tolerance of the optical center frequency control are determined by facet mirror reflectivity and cavity length. The unsaturated signal gain increases with the pumping rate and the maximum signal gain as high as 21-28 dB is obtained near oscillation threshold for various cavity structures. The frequency bandwidth, at which signal gain is decreased by 3 dB from the low frequency value, is 1 GHz at 21 dB signal gain for a 900μm cavity length amplifier. The saturation output power, at which the signal gain is decreased by 3 dB from the unsaturated value, is -10 to -5 dBm. The saturation output power will be improved by 18 dB in a traveling wave type amplifier.

Class E tuned power amplifier with shunt inductor

Abstract: The `class E tuned power amplifier with a shunt inductor' is presented It offers a DC-to-RF power conversion efficiency approaching 100 percent The proposed circuit of the amplifier uses a shunt inductor instead of a shunt capacitor The conditions for optimum operation are formulated and discussed The following are determined: the waveforms, the fundamental-frequency components, the peak values of the collector current and voltage, the output power, and the values of the load network elements Experimental results are also presented The proposed amplifier circuit minimizes the power dissipated during the on-to-off transition, even if the switching time is an appreciable fraction of the signal period

Variable power amplifier

Abstract: A plurality of FET or other amplifiers are connected between respective outputs of an N output port power divider network and respective inputs of an N input power combining network in a variable power amplifier system. A gate bias is selectively supplied to each of the amplifiers which is either at a first value to cause the amplifier to amplify or at a second value to cause the amplifier to be cut off and therefore to not dissipate any DC power. The number of amplifiers receiving the first potential is determinative of the amount of power amplification of the variable power amplifier.

Downhole digital power amplifier for a measurements-while-drilling telemetry system

Abstract: A downhole digital power amplifier comprises a device which, through digital means, provides a sinusoidal, variable frequency, variable power and variably phase-shift modulated output for the transmission of data from a downhole sensor arrangement to an uphole receiver. Selection and variation of frequency, power and modulation are made through digital inputs. The device provides these functions at extra low frequencies (ELF) low-to-high power output, and varying phase-shift keying. The downhole digital power amplifier (68) comprises, in a preferred embodiment, an input shift register (81) for receiving a digital bit stream, a programmable frequency divider (82), a dead man timer circuit (84), a counter (86), a sync circuit (88), a PROM (90) (programmable read-only memory) for generating a digital sinusoidal output, a DAC (92) (digital-to-analog converter) for converting the digital sinusoidal output to an analog sinusoidal output, a power supply control circuit (94), an analog divider (96), and a conventional power amplifier (98). The dead man timer circuit detects normal operation and a fault condition, and controls the power supply control circuit to "power down" the amplifier when reception of a digital bit stream is not imminent during normal operation, and controls the power supply control circuit to periodically generate a "failure informant" message during a fault condition.

A 4-terminal wide-band monolithic amplifier

Abstract: A bipolar monolithic amplifier is described which achieves 18 dB gain, 725 MHz-3 dB bandwidth and 44 dB noise figure The circuit is housed in a 4-lead TO-46 package, consumes 180 mW of DC power and requires no external components Input and output impedances are matched to 50 /spl Omega/ with VSWR less than 15 across the band A high-power version of the circuit consumes 1 W of DC power and gives 152 mW output power at 200 MHz

Class E high-efficiency switching-mode tuned power amplifier with only one inductor and one capacitor in load network-approximate analysis

Abstract: A class E high-efficiency switching-mode tuned power amplifier can be realized with only one inductor and one capacitor in the load network; previously published class E circuits contained at least two inductors and two capacitors. Switch conduction duty ratio and network loaded Q cannot be chosen independently as they can in the circuits published previously. This simplified circuit is appropriate for applications in which the harmonic content and the phase-modulation noise of the output are not important criteria, e.g. in providing RF energy for heating, for generation of sparks, arcs, or plasmas, for communications jamming, or for input drive to a higher power stage; or to a rectifier so that the entire circuit functions as a high-efficiency DC/DC converter. Experimental results and an approximate analysis are given; the two are in good-to-fair agreement.

Circuit means for efficiently driving an electrodeless discharge lamp

Abstract: In an electrodeless discharge lamp of the type including an ionizable medium within a sealed envelope capable of emitting radiant energy when subjected to a radio frequency field, an oscillator for generating an output signal at a given radio frequency of 13.56 MHz, an RF amplifier responsive to the oscillator output signal, and an induction coil and a capacitor connected in series and responsive to the output of the amplifier, the coil being positioned in close physical proximity to the medium in the envelope for coupling to the medium an electric field having a magnitude sufficient to initiate ionization of the medium and a magnetic field for maintaining ionization, there is disclosed an improvement wherein a Class D amplifier drives the series connected coil and capacitor without a separate load circuit connected in the output circuit of the amplifier. A specially selected filter and matching network coupled between the Class D amplifier and the series connected coil and capacitor reduces CV 2 f losses, filters the output of the Class D amplifier to minimize harmonics, and matches the output impedance of the amplifier to the input impedance of the discharge to set the desired light level. The filter and matching network include specially designed induction coils for reducing radio frequency interference. Elements of the filter and matching network are variable to adjust the light level output of the lamp.

Operational amplifier employing complementary field-effect transistors

Abstract: An operational amplifier employing complementary MOSFET transistors includes first and second differential amplifiers respectively employing complementary conductivity type transistors. The input connections of the first and second differential amplifiers connect in parallel to receive the same input signal, the common-mode voltage of which may vary to and include first and second supply potentials. First and second current mirror amplifiers, respectively employing complementary conductivity type transistors, have input connections to which first and second output connections of the first differential amplifier respectively connect, and have output connections connected to an output terminal. Third and fourth current mirror amplifiers, respectively employing complementary conductivity type transistors, have input connections to which first and second output connections of the second differential amplifier respectively connect, and have output connections connected to the output terminal.

Dual-channel data processing system for railroad safety purposes

Abstract: A respective microcomputer is provided for each processing channel in a data processing system constructed according to safety principles. The information to be output to the process are determined by both microcomputers and are supplied in pairs to two non-fail-safe comparators which drive respective AND gates. Each of the AND gates drives a respective amplifier. The power supply of one amplifier occurs from a battery or the like and the power supply of the other amplifier occurs by transformer-coupled output signals of the first amplifier, which signals are then rectified. The information required for the process are coupled via at least one further amplifier whose power supply is provided by a transformer-coupled and rectified output signal of the second amplifier. Given a signal discrepancy between the two microcomputers, information is not permitted to the process which could lead to a dangerous situation.

Cmos operational amplifier with reduced power dissipation

Abstract: Operational amplifier (10) comprised of MOSFET elements which provides for a variable drive for an output stage (18) that results in lower power dissipation and increased gain factor over comparable circuits using constant bias drive for the output stage. A bias section (14) comprised of complementary MOS elements (24, 26) is connected to a single MOSFET (40) that furnishes constant current to the signal input section of a differential amplifier section (20). The output of this differential amplifier is furnished by one path directly to one complementary MOSFET element (72) of a high impedance output stage and by another path to a level shift section (16) which provides an output to a second complementary MOSFET element (80) of the output stage. Thus, the circuit functions under class A-B operation at low power dissipation and provides high open loop gain. Additional embodiments of the invention utilize three MOSFET elements (104, 106, 108) in the level shift section or an additional output stage having an NPN transistor (120) in combination with an N channel MOSFET (122).

Solid state autotune power amplifier

Abstract: A solid state, band-pass filtered, RF power amplifier for equalizing the response of an amplified RF signal across the entire tuning range of a multi channel transmitter is disclosed. An RF signal is applied to the input of a low noise FET amplifier with a portion of the signal coupled off into a frequency counter which in conjunction with a digital switching logic selects a path through a band-pass filter having characteristics that reduce the broadband noise of the RF signal passed therethrough. Additionally, a dual directional coupler samples the output of the power amplifier with the forward sampled signal being used to control the amplifier output to a preselected level and the reverse sampled signal being used to reduce the amplifier output signal in proportion to an increase in the voltage standing wave ratio load between the amplifier and the transmit/receive switch.

A GaAs monolithic low-noise broad-band amplifier

Abstract: Describes the design, fabrication, and performance of GaAs monolithic low-noise broad-band amplifiers intended for broadcast receiver antenna amplifier, IF amplifier, and instrumentation applications. The process technology includes the use of Czochralski-grown semiinsulating substrates, localized implantation of ohmic and FET channel regions, and silicon nitride for passivation and MIM capacitors. The amplifiers employ shunt feedback to obtain input matching and flat broad-band response. One amplifier provides a gain of 24 dB, bandwidth of 930 Mhz, and noise figure of 5.0 dB. A second amplifier provides a gain of 17 dB, bandwidth of 1400 MHz, and noise figure of 5.6 dB. Input and output VSWR's are typically less than 2:1 and the third-order intercept points are 28 and 32 dB, respectively. Improved noise figure and intercept point can be achieved by the use of external RF chokes.

RF Characterization of Microwave Power Fet's

Abstract: The large-signal S-parameter S/sub 22/ and the optimum load for maximum output power are two parameters commonly used in the RF characterization of microwave power FET's. Using a nonlinear circuit model of the device, the dependence on RF power of each of these parameters is investigated. A method is given for computing the optimum load from the Iarge-signal S/sub 22/. Equivalent load-pull data can thus be obtained without the need for load-pull measurements. The gain compression characteristics of the transistor for arbitrary load can be computed from large-signal S/sub 21/, and S/sub 22/ data.

Dual-Gate MESFET Variable-Gain Constant-Output Power Amplifier

Abstract: The use of a dual-gate GaAs FET as a broad-band variable gain and constant output power amplifier is described. A five-stage variable gain-constant output power amplifier has been realized which provides a constant output power of 3 dBm (/spl plusmn/2 dB) for a large dynamic range of input power of -45 dBm to 0 dBm over the 4-8-GHz band. The amplifier uses a feed-forward AGC circuit for preadjusting the gain of the amplifier stages depending upon the strength of the signal at the output of preceding stages. The amplifier has the capability of detecting two or more simultaneous RF pulses having different amplitudes and separated by more than 15-ns time intervals. Also it preserves any amplitude modulation of the individual pulse.

Transformer for driving Class D amplifier

Abstract: In an electrodeless discharge lamp of the type including an ionizable medium within a sealed envelope capable of emitting radiant energy when subjected to a radio frequency field, an oscillator for generating an output signal at a given radio frequency, a Class D RF amplifier including first and second transistors responsive to the oscillator output signal, and an induction coil responsive to the output of the amplifier, the coil being positioned in close physical proximity to the medium in the envelope for coupling to the medium an electric field having a magnitude sufficient to initiate ionization of the medium and a magnetic field for maintaining the ionization, there is disclosed an improved transformer for driving the Class D amplifier which results in a significant decrease in power consumption. The oscillator output signal is connected to the primary winding of a transformer which includes a toroidal, magnetic core. The transistors of the RF amplifier are connected to secondary windings wound on the core. The core is split between the secondary windings to form a high reluctance path which isolates the secondary windings from each other and critically couples the primary winding and the secondary windings.

Prospects for Very High Gradient Linac-Colliders

Abstract: The energy realistically attainable by an electron-positron storage ring is limited by the RF voltage and power requirements imposed by synchrotron radiation to about 100 GeV. To reach energies of 300 × 300 GeV and higher in a colliding beam machine of reasonable dimensions, we must look to the linac-collider operating at an energy gradient on the order of 100 MV/m. Proper choice of an RF structure for such a collider can minimize the total RF power requirement and the effects of longitudinal and transverse single-bunch beam loading. For an operating frequency in the range 4-6 GHz, the total RF power requirement for a 300 × 300 GeV collider with a luminosity of 1032 cm-2s-1 accelerating 1011 particles per bunch is on the order of 50 MW. To drive this collider, RF power sources are needed having a peak output power in the range 1-2 GW. Possibilities for attaining these peak power levels by direct generation and by energy storage and fast switching are discussed.

Performance of Optically Microwave Switching Devices Coupled

Abstract: The performance of optically coupled microwave switching devices for pulse generation or other applications is detailed The bias dependence of the RF power transfer is presented for a range of operating frequencies, thereby establishing the bias conditions required for a given ON/OFF ratio and insertion loss Limits on peak RF power level and pulse repetition rate, as well as limitations arising from harmonic distortion and shot noise, are also examined

Switching power driving circuit arrangement

Abstract: This dual operating mode switching power driving circuit arrangement comprises an amplifying circuit of conventional form which is operated substantially as a Class A feedback amplifier in a servosystem "following" mode and is switched to operate as a Class D amplifier in the "seeking" mode under program control calling for the latter mode and reswitched to the "following" mode only at the succeeding transition of the Class D waveform whereby transients are avoided. For operating in Class D mode, the Class A feedback loop is opened and the amplifier circuit is arranged so that the input wave now overdrives the input circuit and drives the output circuit between ± values of the energy potential, whereby the efficiency is very high. A single electronic switch and logical circuitry connected thereto are arranged to deliver selectively a driving control signal from such input terminals to the input circuit of a conventional amplifier for operating it in the Class A linear second order negative feedback loop arrangement and to deliver an overdriving feedback signal from the output terminal of the amplifier, the duty cycle of which responds to load device current passing a sensing device for operating the amplifier in the Class D mode. Preferably, the application of control signals is under program control along with such control over the operation of the load device.

Icrh antenna design and coupling optimization studies

Abstract: A complete analysis of an ICRH antenna system is given yielding practical criteria for design optimisation relevant to large machines. After having analyzed the screening effect of an electrostatic shield, a solution is presented for the field distribution around an electrostatically shielded antenna from which the effect of the plasma on the loading and the reactance of the antenna can be obtained. A general procedure for the application of these results to multiple antennae system is outlined and practical rules are derived for optimizing the rf power per unit antenna surface coupled to the plasma.

Design, fabrication, and characterization of monolithic microwave GaAs power FET amplifiers

Abstract: The design, fabrication, and characterization of three- and four-stage monolithic GaAs power FET amplifiers are described. Each of the amplifier chips measures 1 mm × 4 mm. Procedures for characterizing these monolithic amplifiers are outlined. Output powers of up to 1 W with 27-dB gain were achieved with a four-stage design near 9 GHz. The circuit topologies used were flexible enough to allow external bondwires to be used as shunt inductors for amplifier operation at C- or S-bands. An output power of 2 W with 28-dB gain and 36.6-percent power-added efficiency was achieved at 3.5 GHz, using a modified four-stage amplifier.

High power, low frequency, electronically adjustable attenuator

Abstract: An attenuator for high-power, low frequency RF signals including two π-section low-pass filters is well matched to the transmission line characteristic impedance. Each of the four loss branches of the attenuator includes a power resistor and a PIN diode. The attenuator is made electronically variable by controlling the dc bias across the PIN diodes, which respond to increased voltage by exhibiting lowered resistance. At any setting of the dc bias, only a fraction of the attenuated RF power is dissipated by the diodes. When the bias voltage is tuned for high attenuation, virtually all of the power is dissipated by the power resistors.

K-Band High-Power GaAs FET Amplifiers

Abstract: Lumped-element internal matching techniques were successfully adopted for K-band power GaAs FET amplifiers. The developed 18-GHz band two-stage amplifier provides 1.05-W power output at 1-dB gain compression and 1.26-W saturated power output with 8.1-dB small-signal gain. The 20-GHz band single-stage amplifier has 1.04-W power output with 3-dB associated gain. Lumped-element internal matching circuit design as well as amplifier fabrication are described. Intermodulation distortion and AM-to-PM conversion characteristics are also presented.

Instantaneous broadband radar signal pulse detector

Abstract: A pulse detection radar signal receiver is disclosed which includes at least one pulse detection channel that has an RF amplifier and a feedback signal path coupling the output to the input thereof for recirculation of signals therethrough. The feedback path includes a signal-to-noise (S/N) enhancer circuit and an inhibiting means, preferably disposed in series therewith. The S/N enhancer circuit is operative to adaptively focus a narrow enhancement bandwidth about the frequency of an input signal, which has a power level greater than a predetermined threshold level, for enhancing signals which have frequencies within said enhancement bandwidth and for attenuating signals which have frequencies outside said enhancement bandwidth. The enhanced and attenuated signals are provided to the input of the RF amplifier for recirculation therethrough. Thus, after one or more recirculations through the loop, an RF pulse signal, which is substantially at one carrier frequency, may be amplified and the RF noise signals, which are broadband in nature, may be attenuated. Accordingly, a weak RF pulse signal, after a number of recirculations, may become distinguishable from the broadband RF noise signals. When the RF pulse signal is detected, the inhibiting means is operated to squelch the circulated signals, momentarily, from passing through the feedback path.

Integrated amplifier arrangement

Abstract: An integrated amplifier arrangement in which the d.c. voltage gain is suppressed, which includes two transistors arranged as a differential pair with an output between the collectors of these transistors. In order to improve the high-frequency properties of the amplifier arrangement, the collector circuit of the transistors includes two load transistors in cascade with the two transistors arranged as a differential pair, each load transistor including an impedance in its base circuit in order to obtain an inductive input impedance on the emitter side of the transistor. In order to obtain direct-current and low-frequency negative feedback for eliminating the d.c. gain, the base electrodes are cross-coupled to the collector electrodes of the load transistors.