Showing papers on "RF power amplifier published in 1968"

A large signal analysis of IMPATT diodes

Abstract: This paper presents results on RF power output and efficiency of IMPATT oscillators obtained from a large-signal model of these devices. The results are obtained from a closed-form solution of the nonlinear equations describing a Read-type IMPATT diode. The closed-form solution is obtained by assuming a short transit time through the drift region compared to the RF period. The solution is used to obtain the large-signal diode impedance. The analysis shows that the power output of an IMPATT diode depends strongly on the series load resistance presented to the active part of the diode and that the change in diode reactance with increasing bias current also depends on the series resistance. Plots of power output as a function of frequency, bias current, and load resistance are presented. Frequency tuning of the oscillator through current variation is also discussed. Experimental results are presented and compared with the theoretical ones wherever possible. The results lead to an improved understanding of such oscillators and are extremely useful in optimizing their performance and determining their limitations.

IF Amplifier using C/SUB c/ compensated transistors

Abstract: An integrated bridge network of four transistors is used as a self-neutralized active element in tuned RLC amplifier designs. The bridge network compensates for the transistor collector-base junction capacitance (C/SUB c/), yielding a 95-percent reduction in the common-emitter reverse transmission admittance. IF amplifier stages that achieve the maximum unilateral power gain of a common-emitter transistor while maintaining excellent alignability are realized using the C/SUB c/ compensated transistor structure. Variations of the relative bias current levels of the transistors in the bridge network provides gain control by way of signal cancellation. This technique produces minimal frequency response variations of the amplifier stage being controlled. A noise analysis shows output signal to noise ratio at maximum attenuation can be a performance limitation.

A high-performance monolithic IF amplifier incorporating electronic gain control

Abstract: A direct-coupled monolithic IF amplifier that incorporates an active gain control stage and exhibits a power gain of 50 dB and an AGC range of 60 dB at 50 MHz is described. This circuit has negligible change in either input or output admittance, and has excellent signal linearity over the full range of gain control. Experimental and theoretical analyses are made of the large signal response, stability, available gain, and noise behavior of the circuit. An application to color television is discussed in which the functions of the 45-MHz IF amplifier and the dc-AGC circuitry are fabricated on a single die.

GaAs laser amplifiers

Abstract: Experimental results are presented on the operational characteristics of GaAs laser amplifiers very closely coupled to a laser oscillator. The separation between the oscillator and the amplifier was varied from 0.2 to 2.0 microns. The amplifiers were made by lapping one end at an angle of 10 to 15 degrees. This angle is several times larger than the critical angle for confinement of radiation in GaAs lasers that is estimated from experimental data to be between 2 and 3 degrees. The measured signal gain is a decaying function of input power and approaches a value of 2 to 4 for large input signals. A maximum amplifier gain of about 150 was obtained for an input signal of 2 mW/mil junction width (corresponding to an optical flux-density of about 8 kW/cm2incident on the input side of the amplifier). At this input power level, the output fluoresence is reduced by about 50 percent and the internal oscillatory modes of the amplifier are almost completely quenched. The ratio of the oscillator output actually coupled into the amplifier to the measured output from the oscillator was estimated from gain saturation measurements. It was found to be inversely proportional to the cleaved separation between the oscillator and the amplifier and was estimated as 0.5 and 0.07 for separations of 0.2 and 2 microns, respectively. The output quantum efficiency of the laser amplifier was demonstrated to be comparable to the output quantum efficiency of a single oscillator. Tests of a new structure for a low-noise, constant-gain laser amplifier are described.

Automatic gain control rf-if amplifier

Abstract: Disclosed is a differential amplifier circuit featuring electronic gain control, and this circuit may be constructed in monolithic integrated form. In one embodiment of the invention, first and second pairs of differentially coupled transistors are connected respectively to first and second differentially coupled input transistors, and the input transistors are connectable to a source of differential input signals. Differential output signals are derived at the outputs of transistors in each of the pairs of transistors, and by applying an automatic gain control (AGC) signal at a node which is common to the transistor pairs, electronic gain control is obtained without a differential signal arising therefrom. In another embodiment of the invention, an output differential amplifier stage is directly coupled to transistors in the first and second pairs of transistors so that any common mode signal present there is rejected in said output stage.

Overload compensation circuit for antenna tuning system

Abstract: A radio receiver is supplied with signals from a high impedance capacitive antenna coupled in series with a low impedance resistive load in the form of the emitter-base circuit of a common-base RF transistor amplifier through a series-tuned circuit, including a varactor diode connected in series with an inductor. A source of DC biasing potential is provided to vary the biasing voltage on the diode in order to change its capacitance to tune the circuit over a predetermined band of frequencies. Overload compensation for the varactor diode is provided by utilizing the automatic gain control (AGC) voltage of the receiver, with the AGC voltage being applied to the base of the RF amplifier transistor to vary the biasing potential thereon. This in turn causes a corresponding variation in the impedance of the emitter-base path of the transistor with an increasing impedance being caused by increased signal levels. As a result, increasing amounts of the signal supplied by the antenna are dropped across the emitter-base path of the transistor at high signal levels, thereby limiting the RF signal level across the varactor diode to prevent rectification of high level signals thereby.

Apparatus for detecting object movement

Abstract: An apparatus for detecting a moving object in a monitored area includes an amplifier, preferably tuned to an ultrasonic frequency and having electromechanical transducers of either resonant or nonresonant type connected to its input and an output and mechanically coupled through the monitored area to form a feedback loop which causes the amplifier to oscillate at its tuned frequency. The amplifier signal level depends upon the state of the monitored area, and any movement therein varies the amplifier signal level as a cosine squared function pulse train. The amplifier output after demodulation is AC coupled to a pulse amplifier, shaper and limited, and then AC coupled to an RC integrating network to produce a DC signal whose level is proportional to the duration of the motionally caused pulse train, and is applied to control a solid state alarm switch. A plurality of pairs of transducers may be connected to each amplifier, and the demodulator and alarm network may be remote from the amplifier and transducers and coupled thereto by radio signals, the electric power line, acoustic coupling through transducers, or by direct wire connection. A plurality of amplifiers of different frequencies may be employed, and corresponding filters may be provided in the demodulating and control networks. Also, a plurality of amplifiers, each modulating an oscillator, may be employed, and coupled to a common demodulator and control network.

Signal path series step-biased multidevice high-efficiency amplifier

Abstract: A high-efficiency transformerless amplitude modulation system with an audio frequency power amplifier having at least two amplifier segments with at least one amplifier device in each, a different level voltage power supply for each amplifier segment, and a bias step between adjacent amplifier segments, and with a modulation output direct DC connection from the AFPA to the RF power amplifier of the system.

Solid state power supply

Abstract: 1300611 Transistor oscillator circuits; modulators UTI 1 Jan 1970 100/70 Headings H3R and H3T A solid state RF power supply for a quadrupole spectrometer comprises an oscillator operating with a series tuned tank circuit coupled to the quadrupole rods, an amplifier being provided in the feedback path from the tank circuit. Coupling between the tank circuit and the quadrupole rods may be by way of a parallel tuned circuit, Fig. 1, or may be direct Fig. 2 not shown. In Fig. 1 the oscillator has a push-pull stage 11, 12, operating into first and second tuned circuits comprised of transformer primary windings 36, 40, and capacitors 35, 38. Quadrupole rods 13 are coupled by parallel tuned circuits comprised of transformer secondary windings 50, 51 and capacitors 52 and 53. Capacitors 41, 43 take feedback from the tank circuits to emitter followers 14, 15 cross-coupled to stage 11, 12. Hot filament bulb 24 in the base circuit has a resistance which increases with feedback and biases the transistors to class C operation. The RF envelope developed in the tank circuit is modulated by transistor 58 in accordance with the difference between a controlling program signal and a signal from RF detector 18, such difference being taken and presented by an integrated circuit operational amplifier 17. Capacitors 63, 64 coupled to the transformer secondary windings 50, 51 provide D.C. voltage output to the quadruple rods in proportion to the RF output. If the transformer windings 36, 40, in the tank circuit are connected directly to the quadruple rods, Fig. 2, not shown, the D.C. rod voltages are obtained from these windings by way of RF chokes and feedback from the tank circuit is obtained from feedback windings on the transformer.

Linearization of a digital phase control power amplifier for dynamo electric machine

Abstract: A digital motor control system compensates for the nonlinearity due to operation from a sinusoidal AC power source. A digital error signal is fed through a variable gain digital amplifier whose characteristics are such that the gain varies so as to correct for the nonlinearities which normally result. The output of the variable gain digital amplifier is used to directly control the transfer of power as, for example, by initiating the conduction of controllable rectifiers. The variable gain digital amplifier acts to vary the gain at two different rates, the second rate being less than the first by some factor of two.

A Linear SCR Control Amplifier

Abstract: A linear general-purpose SCR control amplifier is presented in this paper. This control amplifier is composed of a fire-control circuit and a "bridge" power output circuit. The input signal is used to control the firing angle of the two inverse parallel pairs of SCRs in the full-wave power bridge. The relation between the input signal and the firing angle is designed to be the inverse of the non-linearity introduced by the power circuit. Therefore, the amplifier has an overall linear gain characteristic, it is bidirectional, has a high bandwidth, and exhibits no deadband. The power bridge balancing action is used to absorb the major portion of the negative power pulse caused by an inductive load and therefore improves the efficiency of the amplifier. The linear SCR control amplifier has been built and successfully tested with resistive-inductive loads as well as in a closed-loop positioning servo system. The testing results and the simplicity of instrumentation qualify this control amplifier for industrial applications.

Electrical signal amplifier

Abstract: 1,028,383. Valve and transistor amplifying and gating circuits. RANK-BUSH-MURPHY Ltd. Oct. 29, 1964 [Oct. 29, 1963], No. 42622/63. Heading H3P, H3T and H3W. In a push-pull amplifier, more especially for feeding a reactive load 7, the cathode of each output valve 1, 2 is returned to ground via an un-bypassed resistor 8, 9, respectively, and negative feedback is applied by means of a tertiary winding 13 on the output transformer 5, which is connected, in series with resistor 12 and D.C. blocking capacitor 14, between the cathodes. The output stage is driven by means of a pair of transistors 21, 22 each of which has an individual un-bypassed emitter resistor 25, 26, respectively, the two emitters being connected together by a resistor and D.C. blocking capacitor in series. The arrangement may be switched off, either by opening the positive supply to the screen-grids of the output valves 1, 2 by means of a switch 39, or alternatively by applying a positive pulse via terminal 36 and capacitor 37 to the base of an auxiliary transistor 30. The collector potential of this transistor then goes negative, biasing the output valves 1, 2 to cut-off. In addition, diode 29 common to the emitter circuits of transistors 21, 22 and which is normally conductive, is biased non- conductive, the biases on the transistors 21, 22 then becoming such that these transistors are also cut off.

Ten Watt Coaxial Calorimeter for rf Power Measurement

Abstract: This paper describes a dry static calorimeter intended for the measurement of rf power in coaxial lines. The calorimeter is calibrated with dc power. Its maximum input level is 10 W and the highest frequency of operation is 8 GHz. A detailed analysis of the sources of error is presented. The total estimated uncertainty increases from ±0.1% at very low frequencies to ±0.5% at 8 GHz.

Combination push-pull amplifier and antenna

Abstract: A dipole antenna connected across the input of a transistorized push-pull amplifier. The output of the amplifier is applied to a conventional small RF receiver. A first embodiment includes a filter network connected to the antenna for supplying bias voltage to the amplifier. A second embodiment includes a DC battery for supplying the bias.

The meteorological usefulness of a maser RF amplifier on a highly sensitive X-band weather radar receiver

Abstract: approved Major professor An evaluation of the meteorological usefulness of a maser RF amplifier on an AN /MPS -34 X -band weather radar indicates that there are both advantages and disadvantages to its use. The problems associated with the maser used in this study included tuning problems, loss of gain through loss of liquid helium and from tilting too high, and instability of the gain of the maser with time. The problems encountered which are potentially common to all masers included logistics problems, loss of gain because of saturation of the maser, and sufficient additional sensitivity to the radar receiver system to allow the detection of thermal noise. The detection of thermal noise, predicted by theory for the system used, is the most significant result of the study. Objects at a temperature of 300 K radiate thermal noise which is easily detected by the maser -equipped AN /MPS -34 while on short pulse (MDS< -100 dbm while the noise power for the MPS -34 on short pulse from objects at 300 K exceeds -108 dbm). The advantages of the maser for the detection of clouds, precipitation, fog, clear air turbulence, insects, and birds are investigated. Little advantage is gained by using the maser on sensitive radars for most forms of precipitation except light snow. For sensitive radars, there are definite advantages to using the maser for clouds and bird detection and to some extent for insect detection. An additional 12 db of gain doubles the maximum range of detection for point targets and increases the maximum range of detection for distributed targets four times. Fog and clear air turbulence both have such small reflectivities that the maser did not provide enough additional gain to make detection of these feasible. Several uses of a maser for weather radar are suggested including the study of first echoes and clouds. The addition of a maser to other wavelength radars and to radars of relatively low sensitivity are also considered. THE METEOROLOGICAL USEFULNESS OF A MASER RF AMPLIFIER ON A HIGHLY SENSITIVE X -BAND WEATHER RADAR RECEIVER

a 10-watt S-band solid-state amplifier

Abstract: This paper describes the design and performance of an all-solid-state amplifier, which provided 29.5 dB of gain and 9.1 watts of CW output power in the 100-MHz band from 2.2 to 2.3 GHz. The technique used to measure optimum source and load impedances of a class-C transistor at microwave frequencies is shown. A comparison is made of the performance of several single-stage coaxial class-C designs. Attempts to combine several stages at a scale frequency of 1.15 GHz, using both direct paralleling and hybrid-combining, are discussed. Finally, the results obtained in hybrid-combining sixteen stages to obtain the 9.1 watts of CW output are shown.

A Monolithic Mos-Bipolar Audio Amplifier

Abstract: A one watt AC MOS-Bipolar Audio Amplifier having a voltage gain exceeding 20 db and the pass-band extending to sub-audio frequencies (-3db point of 0.1 Hz) has been designed and integrated. A unique pre-amp employing MOS transistors and a unity gain n-p-n transistor overcomes the disadvantages of the "Unibi" amplifier. Performance characteristics of the breadboard and the integrated amplifier are presented.

Magnetic amplifier welding power sources

Abstract: A power source for arc welding includes a magnetic amplifier, the control winding of which is connected in a control circuit which compares the arc voltage with a standard reference signal. The amplifier is supplied with an alternating current having a frequency between 200 and 2,000 c.p.s. and the control winding is overdriven which results in a drooping characteristic power source having a transient response typical of a flat characteristic power source.