Showing papers on "RF power amplifier published in 1978"
TL;DR: In this paper, the Fourier component analysis of the class E tuned power amplifier was used to determine the effects of deviations from the ideal. Butler et al. showed that with proper output filtering, the amplifier can be operated over nearly an octave bandwidth with less than a 5 percent reduction in efficiency.
Abstract: The operation of the class E tuned power amplifier may be described by a set of equations based on Fourier component analysis. Previous publications have derived an optimum operating mode in which the collector efficiency of an idealized circuit is 100 percent. Since real amplifiers are made from nonideal components and are subject to nonideal loads, it is necessary to determine the effects of deviations from the ideal. The effects of variations in component values and duty cycle are determined from the basic equations. Numerical results of variations in load reactance, shunt capacitance, load resistance, frequency, and duty cycle are presented. The amplifier was found to be quite tolerant of reasonable circuit variations. With proper output filtering, the amplifier can be operated over nearly an octave bandwidth with less than a 5 percent reduction in efficiency.
316 citations
TL;DR: An accurate estimation of the dissipated power is presented, giving more accurate circuit and thermal designs of the class E switching-mode tuned power amplifier.
Abstract: The class E switching-mode tuned power amplifier offers efficiency approaching 100 percent. It is especially applicable at high frequencies because it minimizes the power dissipated during the switching transitions, even if the switching time is an appreciable fraction of the signal period. When the amplifier is properly loaded and tuned, power losses are caused primarily by active-device saturation voltage and resistance, nonzero switching time, and lead inductance. An accurate estimation of the dissipated power is presented giving more accurate circuit and thermal designs.
159 citations
Patent•
06 Jan 1978
TL;DR: In this article, an RF amplifier stage of an AM broadcast tuner is disclosed where, depending upon the power level of the received input signal, said input signal is amplified by a high gain radio frequency amplifier, or by a low gain RF amplifier, and by a combination of both the high and low-gain radio frequency amplifiers at intermediate levels.
Abstract: An RF amplifier stage of an AM broadcast tuner is disclosed wherein, depending upon the power level of the received input signal, said input signal is amplified by a high gain radio frequency amplifier, or by a low gain radio frequency amplifier, or by a combination of both the high and low gain radio frequency amplifiers at intermediate levels. This system provides wide dynamic range and low distortion in that it prevents amplifier saturation and reduces intermodulation product signal levels.
59 citations
01 Jan 1978
TL;DR: A power combining technique for GaAs FET amplifiers using a 12-way divider-combiner has demonstrated a 31% 1dB bandwidth with an insertion loss of 0.25dB and a CW output power of 4.4W at 8.5GHz.
Abstract: A power combining technique for GaAs FET amplifiers will be presented. The approach, using a 12-way divider-combiner, has demonstrated a 31% 1dB bandwidth with an insertion loss of 0.25dB and a CW output power of 4.4W at 8.5GHz.
53 citations
Patent•
17 Apr 1978TL;DR: In this article, an amplifier incorporating various devices for detecting parameters such as average power, peak power and signal voltage is used to provide the feedback signals for automatic level control of an RF amplifier whose output signal is passed through an antenna coupler to an antenna.
Abstract: This disclosure relates to an amplifier incorporating various devices for detecting parameters such as average power, peak power and signal voltage to be used to provide the feedback signals for automatic level control of an RF amplifier whose output signal is passed through an antenna coupler to an antenna. These detection devices allow normal operational level setting as well as minimizing the chance of overloads resulting in amplifier circuit failure during tuning conditions.
53 citations
TL;DR: In this article, large-signal S-parameters are reviewed and transistors of Class-C are employed, and the predicted and measured output power are compared, and suitable conclusions are duly recorded.
Abstract: In this paper, large-signal S-parameters are reviewed, and transistors of Class-C are employed. Problems are encountered in obtaining large-signal parameters S/sub 12/ and S/sub 21/. A novel method is concisely developed based on theory presented herein. The acquired S-parameters are applied to amplifier design accordingly. The predicted and measured output power are compared, and suitable conclusions are duly recorded.
51 citations
TL;DR: In this paper, a Class "G" audio power amplifier has achieved a rated continuous output power of 200 watts and peak power of 400 watts using Power MOS FETs in its output stage.
Abstract: A Class "G" audio power amplifier has achieved a rated continuous output power of 200 watts and peak power of 400 watts. This power amplifier produced no more than 0.01 per cent total harmonic distortion at 20 kHz and 200 watts by using Power MOS FETs in its output stage.
38 citations
TL;DR: A pulsed nuclear magnetic resonance spectrometer suitable for measurements in solids is described in this paper, which uses a versatile pulse programmer and a gated broadband rf power amplifier which delivers 1.6 kW at 60 MHz with a 3db bandwidth of 5 to 90 MHz.
30 citations
Patent•
22 May 1978TL;DR: In this paper, a complementary or quasi-complementary Class B transistor amplifier stage, the output circuits serially connected between relatively negative and relatively positive operating supply voltages to receive direct current and are operated in push-pull with each other for signal to supply a common load from the interconnection of their output circuits, has driver circuitry including a pair of field effect transistors operated in pushing-pull to supply respective halves of the amplifier.
Abstract: A complementary or quasi-complementary Class B transistor amplifier stage, the halves of which have their output circuits serially connected between relatively negative and relatively positive operating supply voltages to receive direct current and are operated in push-pull with each other for signal to supply a common load from the interconnection of their output circuits, has driver circuitry including a pair of field effect transistors operated in push-pull to supply respective halves of the Class B transistor amplifier. A p-channel field effect transistor with source electrode connected to the relatively positive operating supply voltage drives one half of the Class B transistor amplifier stage from its drain electrode, and an n-channel field effect transistor with source electrode connected to the relatively negative operating supply voltage drives the other half of the Class B transistor amplifier stage. The field effect transistors in the driver circuitry are enhancement-mode types permitting their gate electrodes to be connected together to receive input signal potential, avoiding the need for voltage translating circuitry to secure their push-pull operation.
23 citations
Patent•
18 Jan 1978
TL;DR: In this paper, two voltage comparators are activated by a relay operated by the carrier wave of the transmitter so that the comparators function only when the transmitter is operating, and the output signals from the two comparators, together with any other signals indicating a faulty condition, are transmitted to a NAND gate which outputs an alarm signal whenever at least one fault signal is received.
Abstract: A device for monitoring operating conditions of an RF transmitter, including the RF power output thereof, and the reflected voltage wave on a transmission line therefor, and for promptly switching the transmitter off whenever a faulty condition is detected. The device includes two voltage comparators that receive voltage signals representative of transmitter power output and the magnitude of the reflected voltage wave on an associated transmission line, and which generate an output signal whenever a respective voltage signal varies a predetermined amount from a preset reference voltage level. The two voltage comparators are activated by a relay operated by the carrier wave of the transmitter so that the comparators function only when the transmitter is operating. The output signals from the two comparators are transmitted together with any other signals indicating a faulty condition, to a NAND gate which outputs an alarm signal whenever at least one fault signal is received. The alarm signal is then processed to switch off the transmitter and, if desired, to simultaneously switch on an alternate backup transmitter. A third comparator associated with the amplifier circuit for the meter that indicates the transmitter power output is used to provide a transmitter-on condition indication once the transmitter reaches a power level of 2% of its output power after being switched on.
22 citations
01 Feb 1978
TL;DR: In this article, a 3-phase to single-phase power convertor using power transistors in a switching mode as the main power elements has been introduced, which is capable of converting from a fixed 3phase source to variable frequency, controlled output current, such that the operating frequency range is not limited by the supply frequency.
Abstract: A new power convertor, using power transistors in a switching mode as the main power elements, has been introduced. This convertor is capable of conversion from a fixed 3-phase source to variable frequency, controlled output current, such that the operating frequency range is not limited by the supply frequency. The power transformers, inductors and capacitors normally associated with many existing forms of such a convertor are no longer needed. Further advantages of the new convertor are that it is capable of accepting regenerative power, operates without the need for a d.c. link and the input displacement factor is unity, regardless of the output condition.A new mode of operation, that of class ABD, has been introduced, which allows the switching rate of the power transistors to be considerably reduced for a given output. Such a technique reduces switching losses and results in a much less severe operational environment for the power transistors. It also helps to improve the power factor to a value close to unity.The present paper describes a 3-phase to single-phase convertor but the method can be used to provide a fully-regenerative 3-phase to 3-phase static converter, using only 18 power elements and producing a variable frequency, 3-phase controlled output current whose waveform is a very close approximation to a sinusoid.
Patent•
30 May 1978TL;DR: In this article, a system for compensating image contour by modulating a scanning velocity in accordance with a video signal is disclosed, in which a mean current dissipated in a driving power amplifier is detected to control a gain of an amplifier in a preceding stage for suppressing the increase of power dissipation in the power amplifier when the video signal having many noises is received.
Abstract: A system for compensating image contour by modulating a scanning velocity in accordance with a video signal is disclosed, in which a mean current dissipated in a driving power amplifier is detected to control a gain of an amplifier in a preceding stage for suppressing the increase of power dissipation in the power amplifier when a video signal having many noises is received. The preceding stage amplifier is provided with a saturation characteristic to enhance the effect of contour compensation at a small amplitude signal and eliminate over compensation of image contour at a large amplitude signal. The combination of the saturation characteristic and the gain control further enhances the effect of suppression of power dissipation.
Patent•
12 Jun 1978TL;DR: In this article, the authors propose an easy and economical apparatus for protecting the transistors in an H configuration power amplifier by grounding the base input terminals of the power transistors during all times when transistors are switched "off".
Abstract: This invention relates to the protection of power transistors in an H configuration power amplifier which drives a D.C. motor. When the amplifier is switched off, it may be possible for the base terminals of the transistors to be turned "on" which results in the transistors conducting. If two series transistors conduct, the resulting short circuit may damage or destroy the transistors. This invention provides an easy and economical apparatus for protecting the transistors in the power amplifier by grounding the base input terminals of the power transistors during all times when the transistors are switched "off."
TL;DR: In this article, a negative feedback circuit for a moving-coil loudspeaker and a host amplifier is presented. But the feedback signal from the output of the host amplifier in such a way that the velocity of the voice coil of the speaker more closely follows the signal voltage input to the host amplifiers is not considered.
Abstract: A negative-feedback circuit for use with a moving-coil loudspeaker and a host amplifier modifies the feedback signal from the output of the host amplifier in such a way that the velocity of the voice coil of the speaker more closely follows the signal voltage input to the host amplifier. The power output of the power amplifier is delivered to the voice coil through a low resistance, and a high resistance feedback path is provided from each side of this low resistance to the input of the host amplifier. Other reactive and resistive elements may also be used with the high resistance feedback paths for improved operation.
Patent•
23 Oct 1978
TL;DR: In this article, a voltage controlled attenuator is used to attenuate input signals responsive to excessive output levels, but is relatively slow to reduce the attenuation when the output level is subsequently lowered.
Abstract: A circuit for limiting the output power of a power amplifier to a preselected value in order to prevent the amplifier from either clipping the input signal or applying potentially damaging signal levels to a loudspeaker connected to the output of the amplifier. The limiting and clipping circuit includes a voltage controlled attenuator through which the input signal passes before entering the amplifier. The amplifier output is compared to an output reference by a control circuit which supplies an attenuation command to the attenuator whenever the output level reaches the reference level. The value of the output reference can be easily adjusted from a fairly low percentage of the amplifier power capacity to the amplifier's maximum power capacity in which condition the circuit prevents amplifier clipping. The circuit is relatively quick to attenuate input signals responsive to excessive output levels, but is relatively slow to reduce the attenuation when the output level is subsequently lowered. Consequently, the circuitry quickly limits the output to safe and distortion free limits without itself introducing waveform distortion of signals in the audio range. Various embodiments of the invention may be employed depending upon specific circumstances.
Patent•
16 Mar 1978
TL;DR: In this paper, a portable radio receiver powered by battery includes an RF amplifier, an IF amplifier and an audio amplifier powered by a first regulated, switched, DC power converter that derives a first DC voltage.
Abstract: A portable radio receiver powered by a battery includes an RF amplifier, an IF amplifier and an audio amplifier powered by a first regulated, switched, DC power converter that derives a first DC voltage. A frequency synthesizer, including varactor diodes, is powered by a second regulated, switched DC power converter that derives a second DC voltage. Digital circuitry included in the synthesizer is powered by opposite polarity, third and fourth power converters. A synchronizing source for switching all of the power converters simultaneously has a fundamental and harmonics outside of the bandpasses of the audio and IF amplifiers to minimize the injection of spurious signals by the power converters into the amplifiers. The synchronizing source is FM modulated by an audio source so that harmonics of the synchronizing source are spread over a predetermined spectrum and the harmonics have noise-like characteristics spread over relatively wide frequency ranges.
TL;DR: In this paper, two medium-power 12-18 GHz GaAs FET amplifiers, one single-ended and one balanced, have been developed, and a minimum output power across the Ku-band of 200 mW with an associated gain of 4.0 dB was achieved with the balanced module.
Abstract: Two medium-power 12-18 GHz GaAs FET amplifiers, one single-ended and one balanced, have been developed. A minimum output power across the Ku-band of 200 mW with an associated gain of 4.0 dB was achieved with the balanced module. The transistor used in this study has gate dimensions of 300/spl times/1/spl mu/m. The technology, RF performance, and characterization of the transistor are discussed in detail, as are the design and performance of both single-ended and balanced amplifier modules.
Patent•
16 Jan 1978
Abstract: A high fidelity audio amplifier having a pair of cooperating active amplifying devices includes two diodes, each of which is connected in a distinct signal pathway directly associated with an active amplifying device so that the amplifier achieves true Class A operation over the full range of normal input signals. The amplifier can achieve true Class A operation using bipolar transistors, field effect transistors, or vacuum tubes as the active amplifying devices.
01 Jul 1978
TL;DR: An important mode of operation of a general power amplifier using power transistors is described, whose output is a variable-frequency 3-phase current.
Abstract: An important mode of operation of a general power amplifier using power transistors is described, whose output is a variable-frequency 3-phase current. The convertor operates from a fixed 3-phase source without a d.c. link, utilises only 18 power transistors and provides a regenerative output.
Patent•
27 Oct 1978
TL;DR: In this paper, an approach for controlling pulse width in pulsed, step-wise frequency modulated transmitters employing relatively long pulse widths and receiving pulse compression is presented, where individual solid-state, RF power amplifier modules are paralleled, all spares included, and the full parallel group is operated at a power level such that individual units operate substantially below maximum power rating.
Abstract: Apparatus is shown for controlling pulse width in pulsed, step-wise frequency modulated transmitters employing relatively long pulse widths and receiving pulse compression. Also disclosed is a pulsed pseudo-random coded radar system having fixed code word duration. Individual solid-state, RF power amplifier modules are paralleled, all spares included, and the full parallel group is operated at a power level such that individual units operate substantially below maximum power rating. RF solid-state device life is thereby increased. Failures of individual solid-state modules are recognized by a power monitor which operates to lengthen the pulse width in the FM staircase embodiment and to increase power supply input and, therefore, peak pulse power in the pseudo-random coded embodiment, thereby restoring average nominal transmitter power, notwithstanding one or more failed solid-state RF amplifiers.
TL;DR: In this paper, a silicon power transistor for use at X-band has been developed utilizing e-beam lithography and ion implantation, the transistor has a bar size of 0.5 × 1 mm2 and consists of four 27.5× 75µm2 active cells.
Abstract: A silicon power transistor for use at X -band has been developed utilizing e-beam lithography and ion implantation. The transistor has a bar size of 0.5 × 1 mm2and consists of four 27.5 × 75-µm2active cells. With a specially designed package, the combined output power of four cells operating at common base Class C mode is nearly 2 W CW at 8 GHz and almost 1.5 W CW at 10 GHz.
Patent•
06 Mar 1978TL;DR: In this article, a radio frequency burst signal memory system is described, which includes a feedback loop for recirculation of the received RF burst signal when a proper burst signal is detected.
Abstract: A radio frequency burst signal memory system is described which includes a feedback loop for recirculation of the received RF burst signal when a proper burst signal is detected. The output from an RF amplifier is split into separate frequency bands by a diplexer. When one of these bands is sensed at the input, only signals of the sensed frequency band are recirculated.
TL;DR: It is demonstrated that the operation cycle in this type of circuit differs from the one commonly assumed, due to the fact that base widening dominates the feedback effect of the transistor.
Abstract: Comparisons between experiments and simulations on a widely used output stage in mobile transmitters are made. It is demonstrated that the operation cycle in this type of circuit differs from the one commonly assumed. The reason is that base widening dominates the feedback effect of the transistor.
Patent•
10 Oct 1978
TL;DR: In this article, a coaxial switch capable of operating in a vacuum with high RF power in the 1.2 GHz range without "multipactor" breakdown, and without relying on pressurization with an inert gas, which requires a hermetic seal, is achieved by completely surrounding the RF carrying conductors of the switch with a high grade solid dielectric, thus eliminating any gaps in which electrons can accelerate.
Abstract: A coaxial switch capable of operating in a vacuum with high RF power in the 1.2 GHz range without "multipactor" breakdown, and without relying on pressurization with an inert gas, which requires a hermetic seal, is achieved by completely surrounding the RF carrying conductors of the switch with a high grade solid dielectric, thus eliminating any gaps in which electrons can accelerate.
Patent•
03 Nov 1978
TL;DR: In this paper, the output of a power amplifier is connected to its inverting input through a third resistor, and the ratio of the third resistor to the second resistor is selected to be larger than 1 whereby the output impedance of the power amplifier device as seen from the first and second output terminals is made to be negative.
Abstract: A power amplifier device comprising first and second output terminals connected to a loudspeaker, and a power amplifier having a non-inverting input supplied with an audio signal, an output connected to the first output terminal and an inverting input. The second output terminal is grounded through a first resistor and connected to an input of an inverting amplifier having a gain of -1. An output of the inverting amplifier is connected to the inverting input of the power amplifier through a second resistor. The output of the power amplifier is connected to its inverting input through a third resistor. The ratio of the third resistor to the second resistor is selected to be larger than 1 whereby the output impedance of the power amplifier device as seen from the first and second output terminals is made to be negative.
27 Jun 1978
TL;DR: In this paper, it was shown that output powers up to 8W with 1 dB bandwidth of from 1 to 5 GHz can be obtained for GaAs power FET amplifiers at C- and X bands.
Abstract: Lumped-element impedance matching has been used successfully for the design of GaAs power FET amplifiers at C- and X bands. It is shown that output powers up to 8W with 1 dB bandwidth of from 1 to 5 GHz can be obtained.
TL;DR: In this article, the left and right stereo power amplifiers receive power from the 12-volt D.C. automobile supply bypassed by a single capacitor for both amplifiers and energize the speakers in series with the junction of the series connected speakers coupled to ground through a capacitor.
Abstract: Left and right stereo power amplifiers receive power from the 12-volt D.C. automobile supply bypassed by a single capacitor for both amplifiers and energize left and right loudspeakers in series with the junction of the series-connected speakers coupled to ground through a capacitor that allows the left and right speakers to be independently driven by the left and right power amplifiers, respectively, by spectral components above the crossover frequency determined by the speaker impedance and the capacitor impedance. Each power amplifier is driven by an equalizing circuit including a photocell illuminated by an LED that is driven by a feedback signal from the power amplifier.
TL;DR: In this paper, a transistor-distributed amplifier configuration was developed and tested for medium power applications, which achieved a 10 dB gain, 130 ps step response rise time, and a amplitude of 4 V peak to peak across a 50 /spl Omega/ load.
Abstract: In order to build a gigabit/second pulse amplifier for medium power applications a new transistor-distributed amplifier configuration was developed and tested. A five-section amplifier employing 5 GHz f/SUB T/ bipolar transistors has a frequency response from DC to 3.6 GHz. Results achieved were a 10 dB gain, 130 ps step response rise time, and a amplitude of 4 V peak to peak across a 50 /spl Omega/ load.
Patent•
06 Jan 1978
TL;DR: The RF power and video modulation monitoring circuit as mentioned in this paper provides the unique capability of monitoring the performance of a repeater/noise jammer countermeasures system when the system is operating in either the repeater or the noise jamming mode.
Abstract: The RF power and video modulation monitoring circuit of the invention provides the unique capability of monitoring the performance of a repeater/noise jammer countermeasures system when the system is operating in either the repeater or the noise jamming mode In the repeater mode the systems noise level is measured in an unused portion of the countermeasures system frequency band to provide a monitor of system gain and antenna VSWR In the noise mode crystal detection and threshold comparison provides an indication of RF power output In either jamming mode the measurement of AC in the detected output provides a monitor of modulation
Patent•
02 Jun 1978
TL;DR: In this article, an FM trap circuit in an amplifier mounted on a roof top antenna is made operable from inside the home by providing a switch on the amplifier which is responsive to the negative half cycle in an A.C. power signal.
Abstract: An FM trap circuit in an amplifier mounted on a roof top antenna is made operable from inside the home by providing a switch on the amplifier which is responsive to the negative half cycle in an A.C. power signal to disable the trap circuit and a switch in the home for selectively sending a full cycle A.C. power signal or a half-wave rectified signal to the amplifier.