Showing papers on "Linear amplifier published in 1991"
01 Jan 1991
TL;DR: In this paper, the influence of the nonlinear distortions introduced by the high power amplifier (HPA) of the transmitter is examined, and the degradation in power efficiency due to intermodulation effects and backoff operating, as well as spectral degradations are investigated.
Abstract: Orthogonal Frequency Division Multiplexing (OFDM) in conjunction with a 4-DPSK modulation format has been proposed for the future digital audio broadcasting system (DAB), that should provide compact disk sound quality in portable, vehicular and fixed receivers. With properly chosen parameters, this system should be appropriate for both terrestrial and satellite transmission. In this paper the influence of the nonlinear distortions introduced by the high power amplifier (HPA) of the transmitter is examined. In particular, the degradation in power efficiency due to intermodulation effects and backoff operating, as well as spectral degradations are investigated.It is shown for three different kinds of limiting amplifier models, that even with an output backoff (OBO) in the region of 5-6 dB, the degradation of, e.g., a 512-carrier 4-DPSK/OFDM system relative to the linear case is below 1.7 dB, while the regenerated sidelobes of the transmitted spectrum are kept below -20 dB.
712 citations
TL;DR: A multichannel instrumentation amplifier, developed to be used in a miniature universal eight-channel amplifier module, is described and the results of this study are applied to miniature, universal, eight- channel amplifier modules, manufactured with thick-film production techniques.
Abstract: A multichannel instrumentation amplifier, developed to be used in a miniature universal eight-channel amplifier module, is described. After discussing the specific properties of a bioelectric recording, the difficulties of meeting the demanded specifications with a design based on operational amplifiers are reviewed. Because it proved impossible to achieve the demanded combination of low noise and low power consumption using commercially available operational amplifiers, an amplifier equipped with an input stage with discrete transistors was developed. A new design concept was used to expand the design to a multichannel version with an equivalent input noise voltage of 0·35 μV RMS in a bandwidth of 0·1–100 Hz and a power consumption of 0·6 mW per channel. The results of this study are applied to miniature, universal, eight-channel amplifier modules, manufactured with thick-film production techniques. The modules can be coupled to satisfy the demand for a multiple of eight channels. The low power consumption enables the modules to be used in all kinds of portable and telemetry measurement systems and simplifies the power supply in stationary measurement systems.
281 citations
TL;DR: In this article, a clamped bit-line current-mode sense amplifier that maintains a low-impedance fixed potential on the bit lines is introduced, which is achieved by relocating the large bitline capacitance to a node within the sense amplifier, with only a minimal effect on the speed of the circuit.
Abstract: A clamped bit-line current-mode sense amplifier that maintains a low-impedance fixed potential on the bit lines is introduced. Using a general model for active-drive memory cells that include the two-transistor (2T) and three-transistor (3T) dynamic cells and the four-transistor/two-resistor (4T-2R) and six-transistor (6T) static cells, the new sense amplifier is shown to have a response speed that is insensitive to bit-line capacitance. This is achieved by relocating the large bit-line capacitance to a node within the sense amplifier that has only a minimal effect on the speed of the circuit. Bit-line clamping also minimizes inter-bit-line voltage noise coupling. >
199 citations
[...]
TL;DR: In this paper, a 50-MESFET grid unit cell with a gain of 11 dB at 3.3 GHz was proposed, where the grid isolates the input from the output by using vertical polarization for input beam and horizontal polarization for the transmitted output beam.
Abstract: A 50-MESFET grid amplifier is reported that has a gain of 11 dB at 3.3 GHz. The grid isolates the input from the output by using vertical polarization for the input beam and horizontal polarization for the transmitted output beam. The grid unit cell is a two-MESFET differential amplifier. A simple calibration procedure allows the gain to be calculated from a relative power measurement. This grid is a hybrid circuit, but the structure is suitable for fabrication as a monolithic wafer-scale integrated circuit, particularly at millimeter wavelengths. >
148 citations
Patent•
AT&T1
TL;DR: In this article, a multi-stage optical fiber amplifier for gain equalization is proposed, where the amplifier gain can be equalized dynamically to compensate for random variations in the relative optical power of wavelength-multiplexed signals.
Abstract: In this invention there is disclosed a multi-stage optical fiber amplifier for providing a new functon, that of gain equalization. The disclosed multi-stage optical fiber amplifier comprises at least two stages of amplification where each stage comprises an amplifying fiber having a different gain spectrum. In one embodiment the two stages, which can be pumped separately, have different dopant compositions to provide each stage with a different gain spectrum. The disclosed multi-stage optical fiber amplifier provides overall gain spectrum equalization of the amplified channels of long haul transmission lines. Typically, gain equalization can adjust the gain of one channel while maintaining the gain of a second channel constant. When used in combination with automatic gain control, the amplifier gain can be equalized dynamically to compensate for random variations in the relative optical power of wavelength-multiplexed signals to prevent system impairment caused by low-power channels.
123 citations
Patent•
NEC1
TL;DR: In this article, an output level control circuit for a high frequency power amplifier for amplifying high frequency signals having the "on" and "off" periods of transmit signals in a fixed recurrent cycle such as in a TDMA radio communication system or a GSM system is presented.
Abstract: An output level control circuit for a high frequency power amplifier for amplifying high frequency signals having the "on" and "off" periods of transmit signals in a fixed recurrent cycle such as in a TDMA radio communication system or a GSM system. The high frequency detecting circuit for the output level control circuit is responsive to part of the output of the high frequency power amplifier and a control signal corresponding to said "on" and "off" periods of transmission power for generating an output level control signal for the high frequency power amplifier. The high frequency detecting circuit has detecting means for detecting the wave height of the high frequency signals and differential voltage generating means for generating, for each of said recurrent cycles, a differential voltage between the detection output during the "on" period and the detection output during the "off" period immediately preceding it. This differential voltage is used as the temperature-compensated output level control signal for the high frequency power amplifier.
119 citations
Patent•
20 Mar 1991TL;DR: In this paper, a power amplifying apparatus according to the present invention can provide a stable electric power output with wide range by controlling both of the output amplifier for amplifying the electric power and the pre-amplifier disposed at the front of output amplifier, and a stabilizing power source circuit is provided to stabilize the voltage between the power amplifier and the power source for supplying the voltage.
Abstract: A power amplifying apparatus according to the present invention can provide a stable electric power output with wide range by controlling both of the output amplifier for amplifying the electric power and the pre-amplifier disposed at the front of the output amplifier. Furthermore, in order to avoid the disadvantage that a transmission spectrum is expanded because of no supply of a stable voltage to be supplied to the electric power amplifier, thereby producing a cross-talk, a stabilizing power source circuit is provided to stabilize the voltage between the power amplifier and the power source for supplying the voltage.
114 citations
Patent•
22 Apr 1991
TL;DR: In this article, the output power level of a power amplifier is compared with a reference signal (227) to produce a power level control signal (275), which is maintained at the level it had just prior to the transition from an on to an off state.
Abstract: A controlled power amplifier system (211) wherein a sample (225) of the output power level of an on/off switched power amplifier (215) is compared with a reference signal (227) to produce a power level control signal (275) that controls the output power level of the power amplifier (215). When the power amplifier (215) is switched off, the control signal (275) is maintained at the level it had just prior to the transition from an on to an off state. The switching is performed offset from the ends of each switched power amplifier pulse envelope to allow the pulse amplitude to be leveled in the center of the pulse and yet allow the pulse rise and fall times of the pulse envelope to follow the power amplifier input.
88 citations
Patent•
21 Jun 1991TL;DR: In this article, a power amplifier device includes m power amplifier units provided in parallel where m is an integer, a distributor for distributing an input signal to the m power amplifiers, and a combining device for combining m amplified input signals output by the power amplifier to generate an amplified output signal.
Abstract: A power amplifier device includes m power amplifier units provided in parallel where m is an integer, a distributor for distributing an input signal to the m power amplifier units, and a combining device for combining m amplified input signals output by the m power amplifier to generate an amplified output signal. The power amplifier device includes a group of switches for gradually disconnecting the m power amplifier units from the distributor and the combining device and for gradually connecting the m power amplifier units to the distributor and the combining device.
87 citations
Patent•
06 Aug 1991
TL;DR: In this paper, the authors proposed a hybrid matrix power amplifier system, which consists of a series of single-ended low-power amplifiers terminating in an output high-power module, and the output stages are hybrid coupled, and isolators before and after these hybrid coupled output stages isolate the driver from the final amplifiers.
Abstract: RF power is sampled and measured at the input and output of a solid state power amplifier using directional couplers and matched square law detectors. Outputs from the detectors are applied to differential inputs of a DC operational amplifier. Outputs from the detectors are compared and filtered in the operational amplifier and the resulting difference signal is applied to a control input on a switching type power supply. The power supply converts a DC input voltage to the various positive and negative voltages required to operate the RF devices in the solid state power amplifier. When the control loop is closed, the supply voltage varies to maintain a constant operating point resulting in constant gain, efficiency, and linearity for the overall solid state power amplifier despite variations in signal levels and signal composition. In another embodiment, the solid state power amplifier has a series of single-ended low power amplifiers terminating in an output high power module. In the output module, one medium power device acts as a driver stage for four high power devices connected in parallel. The output stages are hybrid coupled, and isolators before and after these hybrid coupled output stages isolate the driver from the final amplifiers and protect the output devices from reflected signals. A dynamically controlled PIN diode variable attenuator at the amplifier input allows the operating point of the amplifier to be selected and adjusted while the closed loop function is in operation. A hybrid matrix power amplifier system is also disclosed.
78 citations
Patent•
06 Feb 1991TL;DR: In this paper, a wave combining circuit for combining the first and second constant-amplitude waves and for generating an output wave was proposed for a wave combination type amplifier with a first amplifier outputting a first amplified output and a second amplifier producing a second amplified output.
Abstract: A constant-amplitude wave combination type amplifier includes a first amplifier outputting a first amplified output, and a second amplifier outputting a second amplified output. The constant-amplitude wave combination type amplifier also includes a first constant-amplitude wave generating circuit for combining an input wave and the second amplified output from the second amplifier and for generating a first constant-amplitude wave which is input to the first amplifier, and a second constant-amplitude wave generating circuit for combining the input wave and the first amplified output from the first amplifier and for generating a second constant-amplitude wave. Further, the constant-amplitude wave combination type amplifier includes a wave combining circuit for combining the first and second constant-amplitude waves and for generating an output wave.
Patent•
28 May 1991TL;DR: In this article, a dual-mode power amplifier is defined, which can be operated in either the linear mode or the saturation mode, depending on the modulation type of the signal.
Abstract: A dual mode power amplifier operable in etiher the linear mode or the saturation mode. The power amplifier, when comprising a portion of a radio transmitter, permits efficient amplification of either a frequency modulated or a composite modulated signal by operation of the amplifier in the saturation mode or the linear mode, respectively. A processor determines the modulation-type of the signal and generates a signal to cause operation of the amplifier in either the saturation mode or the linear mode.
Patent•
01 May 1991TL;DR: In this article, an octave band decade watt power amplifier is disclosed using compact and efficient MMIC fabrication techniques, in which the driver transistor has two cells and the power transistor has four cells, with each power cell double the size of the driver cells.
Abstract: An octave band decade watt power amplifier is disclosed using compact and efficient MMIC fabrication techniques. The power amplifier is a two stage amplifier in which the driver transistor has two cells, and the power transistor has four cells, with each power cell double the size of the driver cells. Both transistors are of an optimized topology facilitating efficient broad band operation at matchable impedance levels. They are interconnected by three four section impedance matching networks of which the input network is coupled to a 50 ohm signal input terminal. The input and the interstage network are both formed on the same substrate as the transistors. The output network is formed on a separate substrate having a high dielectric constant (i.e. 37) which facilitates efficient and compact matching of four power transistor cells to a single output terminal for connection to a load at the conventional (50 ohm) impedance.
Patent•
12 Apr 1991TL;DR: In this article, an Erbium-doped fiber amplifier with multiple stages of amplification for providing enhanced performance is described. But the optical means is located intermediate first and second stages of doped optical amplifying fibers adapted to receive a pump signal at a pump wavelength where the optical medium is adapted to modify the net gain characteristics of the multi-stage amplifier.
Abstract: This invention relates to an Erbium-doped fiber amplifier having multiple stages of amplification for providing enhanced performance. More specifically, optical means is located intermediate first and second stages of doped optical amplifying fibers adapted to receive a pump signal at a pump wavelength where the optical means is adapted to modify the net gain characteristics of the multi-stage amplifier. Presently, all known Erbium-doped fiber amplifiers utilize relatively simple single stage amplifiers which support required ancillary optically passive components such as isolators, filters, pump multiplexers, power monitors and the like at either end of the amplifier. This requirement of having the passive optical element at an end of thhe optical amplifier not only lends to relatively stringent design and fabrication tolerances for a high performance optical amplifier, but it restricts the design of the Erbium-doped fiber amplifier to an embodiment which prevents exploitation of the various unique properties of the Erbium-doped fiber amplifier.
19 May 1991
TL;DR: In this paper, a linearized power amplifier suitable for low power portable radio applications is described, and one narrow-band and one wide-bandwidth application are investigated. But the power amplifier performance was not evaluated.
Abstract: A linearized power amplifier suitable for low-power portable radio applications is described. One narrow-bandwidth and one wide-bandwidth application are investigated. Up to 40% power-added efficiency can be achieved for a 20-dB reduction of the third-order intermodulation products at 1.5 MHz from the carrier frequency in the wide-bandwidth system. Less than -60 dB out-of-band emission and 38% power-added efficiency can be obtained for a narrow-bandwidth system. >
Patent•
15 Nov 1991TL;DR: In this paper, an amplifier (102) which can be dynamically biased is disclosed, where a controller determines when to change the bias level of the amplifier in order to achieve low frequency splatter.
Abstract: An amplifier (102) which can be dynamically biased is disclosed. A controller (118) determines when to change the bias to the amplifier (102), in order to achieve low frequency splatter. This is accomplished by changing the bias level of amplifier (102) between a substantially linear (class A) mode of operation, and a substantially nonlinear (class B) mode of operation. During the critical periods when the amplifier (102) is being turned into and out of operation, the amplifier (102) is placed in a substantially linear mode of operation, thereby reducing the output harmonics which develop. In another aspect of the invention a radio (300) which employs a dynamically biased amplifier (102) is disclosed.
Patent•
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18 Jun 1991
TL;DR: In this article, a low-power crystal-controlled CMOS oscillator with a long and wide additional transistor is provided in the first stage of the output amplifier to prevent it from diverting too much current from the primary amplifier stage during start-up.
Abstract: A low-power crystal-controlled CMOS oscillator wherein a long and wide additional transistor is provided in the first stage of the output amplifier. This prevents the output amplifier from diverting too much current from the primary amplifier stage during start-up.
Patent•
08 Nov 1991TL;DR: In this article, a power control circuit used for both analog/digital dual mode is disclosed, which comprises a switching circuit (17) for applying the feedback signal to the gain control terminal (40) of the power amplifier (2) and applying a fixed bias voltage to the attenuation control terminal(30) of a variable attenuator (10) so that the amplifier operates as a C class amplifier in the case of analog mode, and a voltage control unit (VCU) for controlling the bias voltage.
Abstract: A power control circuit used for both analog/digital dual mode is disclosed which comprises a switching circuit (17) for applying the feedback signal to the gain control terminal (40) of the power amplifier (2) and applying a fixed bias voltage to the attenuation control terminal (30) of the attenuator (10) so that the amplifier operates as a C class amplifier in the case of analog mode, and for applying the feedback signal to the attenuation control terminal (30) of the variable attenuator (10) and applying the predetermined bias voltage to the gain control terminal (40) of the power amplifier (2) so that the amplifier operates as an A class amplifier in the case of digital mode. In the present invention, as a single amplifier operates for both analog mode and digital mode, the configuration is simplified and assembled cheaply.
Patent•
11 Jul 1991TL;DR: In this article, a predistortion filter is connected upstream of the amplifier circuit, and an aggregate signal ##EQU1## is formed in said filter from the input signal s(t).
Abstract: A process for compensating nonlinearities in an amplifier circuit. An input signal s(t) is amplified to form an output signal y(t) using an amplifier circuit subject to nonlinearities. In accordance with the invention, a predistortion filter is connected upstream of the amplifier circuit. An aggregate signal ##EQU1## is formed in said filter from the input signal s(t) and a predistorted signal x(t) fed back from the output of the predistortion filter, and integrated with respect to time. The predistorted signal x(t) is fed to the amplifier circuit subject to nonlinearities. In this case, the prescribed number n+1 of coefficients k0, . . . , Kn is determined in accordance with the model ##EQU2## so that for a given input signal x(t) of the amplifier circuit the output signal determined in accordance with the model is essentially identical with the output signal y(t) of the amplifier circuit.
Patent•
08 Aug 1991TL;DR: In this paper, the authors proposed a transmission output control circuit for a TDMA system radio transmitter and the like and to stably and highly precisely control a transmissionoutput burst wave for a wide range.
Abstract: PROBLEM TO BE SOLVED: To use the title transmission output control circuit for a TDMA system radio transmitter and the like and to stably and highly precisely control a transmission output burst wave for a wide range SOLUTION: Feedback control for controlling the output of a transmission power amplifier 3 with the error voltage (Vcont) of a comparison error amplifier 9 and feed forward control for previously controlling the output level of a variable output drive amplifier 2 so that the input level of the transmission power amplifier 3 is optimized in such a way that the output control characteristic of the transmission power amplifier part 3 always has almost constant control sensitivity are executed. Then, the ramping waveform of the rise and fall of transmission output is controlled and the transmission output level is controlled.
Patent•
06 Nov 1991TL;DR: In this paper, a system for controlling the power level of RF signals output by a portable radio transmitter having a first voltage supply, a first amplifier stage and a microcomputer coupled to the first amplifier for selecting one of a set of power levels is presented.
Abstract: A system for controlling the power level of RF signals output by a portable radio transmitter having a first voltage supply, a first amplifier stage and a microcomputer coupled to the first amplifier stage for selecting one of a set of power levels. An indicator signals when the radio transmitter is coupled to a vehicular voltage supply and, in response, the microcomputer generates a control signal representative of a desired power level. A second amplifier stage is coupled to the first amplifier stage and receives RF signals at the selected power level. A constant gain control circuit coupled to the second amplifier stage receives the control signal and responds by setting the gain of the second amplifier stage at one of at least two constant gain values so that the output RF signals are provided with the desired power level.
Patent•
15 Jul 1991TL;DR: In this paper, a power amplifier system suitable for a mobile radio receiver/transmitter is described, where a wave form signal to be transmitted is made smooth during its rise and fall times, thereby making it possible to prevent a transmission spectrum from expanding and interfering with the adjacent channels.
Abstract: A power amplifier system suitable for a mobile radio receiver/transmitter is described. A wave form signal to be transmitted is made smooth during its rise and fall times, thereby making it possible to prevent a transmission spectrum from expanding and interfering with the adjacent channels. The power amplifier system compares an envelope signal of an inputted RF signal and that of an RF signal to be outputted, whereby the power amplifier system as a whole provides linear amplification.
Patent•
19 Feb 1991
TL;DR: In this paper, the average or DC component of the digital signal was determined by converting the output of an electrocardiographic amplifier into digital format and generating a digital correction word, which was then converted into analog form and fed back into the input of the amplifier to cancel out the DC offset.
Abstract: Biomedical information is directly digitally telemetered from the patient through a frequency modulated transmitter to a remote receiver and computer station. DC offset on the biopotential leads and signals from the patient is compensated by converting the output of the amplifier, such as an electrocardiographic amplifier, into digital format, determining the average or DC component of the digital signal, and generating a digital correction word which is then converted into analog form and fed back into the input of the electrocardiographic amplifier to cancel out the DC offset. The same circuitry is used to insert a standard test signal instead of a correction signal and the output of the amplifier is then checked not to determine its DC component, but to determine whether or not the gain of the electrocardiographic amplifier is performing at a predetermined calibration point. If not, a digital correction word is generated and provided as a correction signal to the programmable gain amplifier.
Patent•
04 Mar 1991TL;DR: In this article, the authors proposed a method for post-distortion correction of phase modulated RF signals by modifying complex modulating signals I,Q in a way that compensates for the amplifier phase error φ e as a function of amplifier power P.
Abstract: Distortion introduced in phase modulated RF signals by amplifiers and other signal processors is substantially reduced by modifying complex modulating signals I,Q in a way that compensates for the amplifier phase error φ e as a function of amplifier power P. In a preferred embodiment, I, Q are combined to calculate the amplifier power level and scaled by a parameter, e.g., K1=-dφ e /dP, to provide factor B so that compensated signals I"=AQ+BI and Q"=AI-BQ, where A is a constant, can be determined. When an RF carrier modulated by I", Q" is passed through the distorting amplifier the amplifier induced distortion is cancelled. Substantial reduction in bit error probability is obtained. The method can also be used for post-distortion correction.
Patent•
AT&T1
TL;DR: In this article, an optical communication system including a doped optical fiber amplifier such as, for example, an erbium doped amplifier, is provided with an amplifier pump which operates at approximately 1.48µm.
Abstract: In this invention telemetry information is transmitted in an optical fiber communication system by providing an amplifier pump (74) with excess power beyond that necessary to pump the amplifier (51). The excess power is not used to pump the amplifier but is rather used to transmit the telemetry information. In a specific embodiment, an optical communication system including a doped optical fiber amplifier such as, for example, an erbium doped amplifier, is provided with an amplifier pump which operates at approximately 1.48µm. The amplifier pump is provided with excess power so as to transmit telemetry information. In a specific embodiment, the telemetry signal can be detected with a low cost photodetector (54) at a subsequent station.
Patent•
15 Apr 1991TL;DR: In this paper, a feed forward amplifier network employing a frequency swept pilot tone signal is proposed to reduce the distortion generated by the network's power amplifier, which is then detected by a detector, phase locked to the variable frequency oscillator, in order to ascertain the average pilot tone energy remaining within the amplified output signal.
Abstract: Briefly described the present invention is a feed forward amplifier network employing a frequency swept pilot tone signal in order to reduce the distortion generated by the network's power amplifier. A frequency swept pilot tone, generated for example by a variable frequency oscillator, is injected into the input path of the power amplifier's input signal. Thereafter, distortion cancellation employed to generate an amplified output signal, substantially free of both pilot tone and the distortion signals generated by the power amplifier. The amplified output signal is then detected by a detector, phase locked to the variable frequency oscillator, in order to ascertain the average pilot tone energy remaining within the amplified output signal. In response to a detection, various amplifier network characteristics are adjusted in order to reduce the amount of pilot tone at the amplifier network output.
Patent•
08 Aug 1991TL;DR: In this article, a power amplifier is provided for a cellular telephone of the type capable of operating in both analog and digital modes, which can operate efficiently in both the analog and the digital modes of operation.
Abstract: In a cellular telephone of the type capable of operating in both analog and digital modes, a power amplifier is provided which can operate efficiently in both the analog and digital modes of operation. The power amplifier includes a non-linear power amplifier stage and a linear power amplifier stage which are controlled by a switching means. During the analog mode of operation, the switching means causes the non-linear amplifier stage to amplify the RF signals. During the digital mode of operation, the non-linear amplifier amplifies the RF signal when there is a requirement for a relatively low power output. During the digital mode when there is a requirement for a relatively high level output, the switching means causes the non-linear power stage and the linear power stage to amplify the RF signals.
01 Dec 1991
TL;DR: In this paper, a 2-24 GHz distributed matrix amplifier and a 1-20 GHz 2-stage Darlington coupled amplifier based on an advanced HBT MBE profile that increases the bandwidth response of the distributed and Darlington amplifiers by providing lower base-emitter and collector-base capacitances are presented.
Abstract: The designs and performances of a 2-24 GHz distributed matrix amplifier and 1-20 GHz 2-stage Darlington coupled amplifier based on an advanced HBT MBE profile that increases the bandwidth response of the distributed and Darlington amplifiers by providing lower base-emitter and collector-base capacitances are presented. The matrix amplifier has a 9.5 dB nominal gain and a 3-dB bandwidth to 24 GHz. This result benchmarks the highest bandwidth reported for an HBT distributed amplifier. The input and output VSWRs are less than 1.5:1 and 2.0:1, respectively. The total power consumed is less than 60 mW. The chip size measures 2.5*2.6 mm/sup 2/. The 2-stage Darlington amplifier has 7 dB gain and 3-dB bandwidth beyond 20 GHz. The input and output VSWRs are less than 1.5:1 and 2.3:1, respectively. This amplifier consumes 380 mW of power and has a chip size of 1.66*1.05 mm/sup 2/. >
01 Apr 1991
TL;DR: In this paper, a two-stage high-efficiency, high-power 8.76 GHz traveling-wave tube amplifier is presented, with peak power of 410 MW over the complete pulse duration, with a conversion efficiency from the electron beam to microwave energy of 45%.
Abstract: Results are presented on the development of a two stage high‐efficiency, high‐power 8.76‐GHz traveling‐wave tube amplifier. The work presented augments previously reported data on a single stage amplifier and presents new data on the operational characteristics of two identical amplifiers operated in series and separated from each other by a sever. Peak powers of 410 MW have been obtained over the complete pulse duration of the device, with a conversion efficiency from the electron beam to microwave energy of 45%. In all operating conditions the severed amplifier showed a ‘‘sideband’’‐like structure in the frequency spectrum of the microwave radiation. A similar structure was apparent at output powers in excess of 70 MW in the single stage device. The frequencies of the ‘‘sidebands’’ are not symmetric with respect to the center frequency. The maximum, single frequency, average output power was 210 MW corresponding to an amplifier efficiency of 24%. Simulation data is also presented that indicates that the...