Showing papers on "RF power amplifier published in 1986"

Binary Peak Power Multiplier and its Application to Linear Accelerator Design

Abstract: This paper describes a new method of pulse compression, the binary power multiplier (BPM), a device which multiplies RF power in binary steps. It comprises one or more stages, each of which doubles the input power and halves the input pulse length. Practical designs are described and expressions for their compression efficiency are derived. The usefulness of pulse compression for accelerator design is illustrated and compared with the pulse compression system currently in use at the Stanford Linear Accelerator Center.

Class E tuned power amplifier with nonsinusoidal output voltage

Abstract: An analysis is presented of the amplifier for a limiting case when the load network does not contain a series-resonant output circuit and the output voltage is non-sinusoidal. For optimum operation with any switch-duty ratio, the author has determined the current and voltage waveforms, the collector current and collector-emitter peak values, the output power, the power-output capability, and the load-network component values. The spectrum of the output voltage is given for a switch-duty ratio of 0.25, 0.5, and 0.75. Close-approximation equations are given for transistor power losses and collector efficiency. The experimental and theoretical results are in very good agreement. The measured collector efficiency is 95%. The circuit has practical applications, e.g., in high-efficiency switching-mode DC-to-DC converters used in DC power supplies for microcomputers or communication equipment.

Automatic output control circuitry for RF power amplifiers with wide dynamic range

Abstract: Automatic power output control circuitry is disclosed in which the magnitude of a radio frequency signal is maintained at one of a plurality of magnitudes selected in response to control signals The radio frequency signal output from a variable output amplifier is sampled and the sample is further amplified and the dynamic range compressed prior to being rectified The rectified power magnitude signal, which is nonlinearly related to the radio frequency signal magnitude, is adjusted by an adjustment factor selected by the control signals and employed in varying the output of the variable output amplifier to produce a corresponding radio frequency signal output magnitude

High efficiency RF power amplifier

Abstract: A high efficiency RF power amplifier is disclosed in which a field effect transistor is operated in a class F mode. A third harmonic quarterwave open circuit transmission line stub having a Z O adjusted to provide capacitance series resonant with transistor inductance at the second harmonic is coupled to the transistor output lead to produce a low impedance at the channel drain of the transistor. Parallel resonance of the transistor die capacitance and interconnect inductance coupled to ground by the transmission line produces a third harmonic high impedance at the channel drain. Further lowpass output matching circuitry provides a constantly increasing impedance magnitude from the transistor die to the load and provides load mismatch isolation to the second and third harmonic impedances at the channel drain.

RF power amplifier with load mismatch compensation

Abstract: An RF power amplifier for delivering power to a load including a first quadrature hybrid coupler driving two class C amplifiers operating with high input compression, a second quadrature hybrid coupler coupled to the outputs of the amplifiers, an attenuator, and a phase shifter. An impedance mismatch by the load causes phase-pulling of the amplifiers which reduces output to the load. This is compensated for by feeding an error signal, indicating the magnitude and phase of the phase-pulling of the two amplifiers, from the second quadrature hybrid coupler through the attenuator and the phase shifter back to the first quadrature hybrid coupler. The attenuated and phase shifted error signal adds to or is subtracted from the input signals to the two amplifiers. Therefore, one of the two amplifiers is driven with more signal and the other amplifier is driven with less signal to phase-push the two amplifiers to compensate for the phase-pulling to thereby increase the output to the load.

Low-noise power-efficient oscillators: theory and design

Abstract: The paper proposes a new linear theory with experimental verification which shows how the spectrum of a high-efficiency oscillator varies with the amplifier noise figure (F), the voltage gain of the amplifier (G), the unloaded quality factor of the resonator (Qo), the loaded quality factor (QL) and the total RF power in the oscillating system (PFED). By defining the parameters, F, G, PFED, QL and hence QL/Qo fundamentally and precisely, the theory shows that F, G and QL/Qo are interdependent. The noise equation is therefore expressed in only a few variables, F, Qo, QL/Qo and PFED. Optimum operating conditions occur when the differential of sideband noise with respect to QL/Qo = O, so that if F is assumed to be constant, minimum sideband noise occurs when QL/Qo = 2/3. Many LC oscillators therefore operate far from the point at which minimum sideband noise occurs. By defining the oscillator power as the total power in the system, the variation of sideband noise power with DC input power can be described, permitting the optimum design of oscillators with minimum sideband noise for any given DC input power. Based on this theory a new highly efficient oscillator configuration has been designed satisfying this criterion. This configuration also reduces the pulling effect of the load sufficiently to permit its use directly as a transmitter. Experimental verification of the theory has been obtained at 1 MHz between the limits 0.09 < QL/Qo < 0.93. A 150 MHz low-noise oscillator, designed using the same approach, has been successfully demonstrated.

Influence of RF power on properties of a-Si1−xGex:H prepared by RF glow discharge decomposition

Abstract: The electrical and structural properties of hydrogenated amorphous silicon germanium alloys prepared by the rf glow discharge method have been measured as a function of the rf power and the gas flow rate. The photoconductivity of a-Si1-xGex:H films increases by a factor of 103 at x=0.45 with increasing rf power density, and the microstructure of the films changes from heterogeneous to homogeneous. This paper discusses the deposition mechanism inducing these results.

Transmit/receive module for phased array antenna system

Abstract: A phased array antenna system includes a plurality of active radiating antenna elements each of which is driven by and each of which drives a transceiver module located closely adjacent thereto. Each transceiver module includes a high-power pulse signal-transmitting amplifier powered by a high-capacitance, low current dc rectifier system to minimize charging currents and provide very high pulse currents, and a low-noise amplifier for amplifying the received signal. The modules further include a transmit/receive switch, phase adjusting circuits in the input to the high-power signal-transmitting amplifier and in the output to the low-noise signal-receiving amplifier for normalizing the signal phase, and amplitude limiting means in the input of the low-noise signal receiving amplifier for protecting the low-noise amplifier during the transmit mode. The transceiver module utilizes microstrip line technology to provide tuned circuit elements, is compact in size and low in cost, and permits an improvement in noise, gain, and radiated power characteristics to be realized in phased array radar systems.

A Power Distributed Amplifier Using Constant-R Networks

Abstract: This paper describes the design, implemental ion and performance of a power distributed amplifier with a minimum gain of 5dB , input and output VSWR less than 1.5:1, and greater than 22dBm of 1dB compressed power over the 2 to 18GHz band. This amplifier makes use of several circuit design advances to improve both bandwidth and power capability and measures 1.0mm by 1.4mm (1.4 sq. mm).

Apparatus for controlling output power of transmitter

Abstract: An apparatus for controlling the output power of a transmitter that is installed in a vehicle or used in a mobile radio communication equipment has a power amplifier, a coupler for delivering an output corresponding to the output power from the power amplifier, a detector disposed after the coupler, a comparator for delivering an output proportional to the difference between the output voltage from the demodulator and a reference voltage, and a voltage control circuit for controlling the output power of the power amplifier in response to the output from the comparator. An RF variable attenuator is disposed before the comparator to compress the dynamic range of the signal applied to the voltage control circuit.

ICRF fusion reactivity enhancement in tokamaks

Abstract: A systematic study of ICRF fusion reactivity enhancement has been conducted, using a new bounce-averaged two-dimensional Fokker-Planck code. Second-harmonic heating of deuterium in a 50–50 DT plasma is assumed, and the results are obtained as a function of background plasma density and temperature. An enhancement factor of ten is achieved at low Q (= fusion power/RF power), which is important for ion-tail diagnostics, but at Q = 0.5 the enhancement is 2. Significant poloidal variations in ion density (up to 14%) and in fusion reactivity (by a factor up to 2.5) are found.

A 19-Way Isolated Power Divider Via the TE/sub 01/ Circular Waveguide Mode Transition

Abstract: A 19-way waveguide isolated power divider has been developed with broad bandwidth, low insertion loss and high isolation. Its design allows a flexible number of output ports and uneven power distribution. It can be used as a feed network for an antenna array and, due to this power divider's high isolation characteristics, it can be used as a power combiner for a high power amplifier.

Adaptively stabilized RF amplifier

Abstract: An output transistor of an RF power amplifier remains stable so that it does not generate subharmonic spurious outputs. An adaptive stabilization network maintains the stability of the output by decreasing the impedance presented to the output transistor when voltage levels at the output transistor exceed a predetermined level. A combination consisting of a peak detector coupled to a Zener diode senses the predetermined level. A PIN diode couples to the Zener diode and to the output transistor so that the PIN diode becomes forward biased when the predetermined level is exceeded.

A Design and Packaging Technique for a High-Gain, Gigahertz-Band Single-Chip Amplifier

Abstract: Equalizing amplifiers for gigabit optical fiber transmission systems requires a 65-dB gain (S21) with a gigahertz bandwidth. However, this gain has the potential to cause significant parasitic oscillation. Consequently, developing a useful stabilization design technique is a very important factor in attaining practical design. In this paper, stabilization design techniques are described for circuit configurations, packaging, and stability assessment. In addition, fabrication results of amplifier IC based on bipolar super self-aligned process technology (SST) and new wide-band high isolation package with coaxial-like 50-/spl Omega/ signal lines are also shown. A 65-dB gain, 1.3-GHz bandwidth single-chip amplifier has been successfully fabricated.

Wideband 1.5μm optical receiver using travelling-wave laser amplifier

Abstract: A high-sensitivity, wideband optical receiver using a travelling-wave laser amplifier in conjunction with a PIN photodiode and commercial 50Ω amplifier is described. A sensitivity of -37 dBm at 1 Gbit/s has been achieved, with a 17dB net amplifier gain.

Drive circuit with limited signal transition rate for RFI reduction

Abstract: An amplifier applies turn-on bias to the gate electrode of an output field-effect transistor in response to a first level of an input signal applied to the amplifier. A switched power source supplies operating current to the amplifier for developing the turn-on bias when the amplifier input signal is at the first level. A feedback-controlled bypass circuit diverts a portion of the operating current from the amplifier during an initial turn-on period and gradually reduces the magnitude of the diverted operating current as the output transistor turns on thereby producing a "soft" turn-on of the output transistor so as to minimize a potential for creating radio frequency interference in nearby RFI sensitive devices such as the tuner in a television or radio receiver. Complementary circuits include dual current supply and diversion circuits providing controlled rise and fall times for complementary field-effect output transistors.

Quasi auto-zero circuit for sampling amplifiers

Abstract: A sampling amplifier (22) consisting of a series combination of a signal input terminal (12), a first capacitor (C1), a first amplifier (A1), a second capacitor (C2), a second amplifier (A2), and a signal output terminal (VOUT2) is able to sample at a higher frequency by providing a low impedance path between the signal output terminal (VOUT2) and a junction (VOUT1) between the first amplifier (A1) and the second capacitor (C2) to quasi auto-zero the amplifier between samples.

Pulse width modulator for AM-RF transmitter

Abstract: An RF-AM transmitter of the type including a power pulse amplifier driving an RF amplifier with a modulating voltage via a low pass filter includes a pulse width modulator for deriving variable frequency pulses having a frequency that is a direct function of an RMS like function of the amplitude and frequency of an information source; the width of the pulses is determined by the instantaneous amplitude of the information signal source. The pulse width modulator includes a constant amplitude, variable frequency triangular wave voltage controlled oscillator responsive to a DC signal representing the frequency and amplitude of the information source. In response to amplitude crossovers between the variable frequency triangular wave and the information source, transitions in the pulse width modulated wave are derived.

Efficient master-oscillator-amplifier system utilizing copper vapor laser active elements

Abstract: An investigation was made of the temporal, spatial, and energy characteristics of a system consisting of a master oscillator, a spatial filter, and a power amplifier constructed on the basis of GL-201 and UL-102 sealed commercial laser active elements. The questions of raising the operating efficiency of such a system and obtaining high-power radiation with the diffraction-limited divergence were considered. When GL-201 active elements were used in the oscillator and amplifier, the radiation output power in a beam having a divergence close to the diffraction limit was 30-35 W. This was 3-4 times higher than the output power of the oscillator alone.

Principles of a resonant cavity optical modulator.

Abstract: We describe the principles of a resonant cavity optical modulator capable of modulation frequencies in the 10-GHz range. The dispersive properties of waveguides are used to achieve phase matching of the optical and rf waves, which differ in velocity by a factor of 3 in bulk electrooptic materials. The difference in propagation velocities also allows us to form a rectangular cavity with two opposite sides open through which the optical beam may be easily passed. A modulator employing this design is thus both efficient in its use of rf power and is easily optically aligned.

Development of radio frequency induction plasma generators for neutral beams

Abstract: The techniques, operational aspects, and experimental results of a radio frequency induction plasma generator, with an internal rf power coupler, intended for intense neutral beam applications are described. One of the development sources suitable for 10×10‐cm2 extraction optics was operated to a deuterium ion current density of 250 mA/cm2, uniform to 5%, over a circular extraction area 15 cm in diameter with a coupled rf power of 20 kW. Temporal fluctuation levels in the extracted ion current were measured to be typically 1% of the dc level. A second developmental source suitable for 10×40‐cm2 grid sets was operated to 200 mA/cm2, uniform to ±8% over a 10×40 cm2 area, with 40‐kW coupled rf power.

Lightweight, high power audio amplifier and power supply

Abstract: An audio amplifier and power supply having a power transformer with power supply and control means to provide pulses of electrical energy at a substantially constant supply voltage, with the duration of the pulses being dependent upon a value that is related to the demands of the amplifier The transformer charges a power capacitor to a substantially constant voltage to supply power for the amplifier The frequency range of the pulses is between about 400 to 2,000 cycles per second, with a frequency being at about 1,100 cycles per second in a preferred embodiment

Two stage push-pull MOSFET power amplifier

Abstract: A power amplifier includes an output stage comprising a pair of complementary MOSFET power transistors connected in push-pull fashion between the positive and negative poles of a split DC power supply, with the sources of the transistors connected together to ground. The input stage includes another pair of complementary MOSFET driver transistors having their gates connected together to the input signal. The drain signal of each of the driver transistors is resistor coupled to the gate of one of the power transistors, and biased so that the driver turns off as the power transistors turns on. The amplifier output signal is taken between the common point of the split DC power supply and ground.

The cell enhancer

Abstract: A cell enhancer or (reradiation system) has been in service along a six mile section of the Schuylkill Expressway near Philadelphia since October, 1984. Its 20 db improvement in radio signal levels has changed the service quality from one of noise, interference and dropped calls to that of good quality communications. Since its initial installation, the performance of this system has been monitored closely with signal levels recorded on numerous occasions. A cell enhancer consists of a broadband class A RF amplifier preceded by two 10 MHZ wide filters. The single amplifier is used to retransmit mobile signals to the cell site and cell site signals to mobiles. A directional antenna is aimed at the serving cell and another antenna is aimed at the coverage problem area. The intent of this paper is to share the experiences of a cellular service provider who has utilized this new technology and concluded that cell enhancers can improve system performance in a cost effective manner.

Polarisation-dependent gain spectrum of a 1.5 μm travelling-wave optical amplifier

Abstract: We present high-resolution gain spectra measurements of a 1.5 μm near-travelling-wave amplifier for both TE and TM polarisation. We use 49km of single-mode fibre at the amplifier input to demonstrate a reduction in the effective bandwidth of the amplifier caused by a combination of dichroism in the amplifier and the polarisation dispersion present in long lengths of fibre.

CMOS Current sense amplifiers

Abstract: A CMOS current sense amplifier circuit for providing a high speed of operation includes a sense amplifier, a dummy sense amplifier and an operational sense amplifier. A memory array is formed of a plurality of core transistors which are arranged in a plurality of rows of word lines and a plurality of columns of bit-lines. A dummy bit-line is formed of a plurality of core transistors which are arranged in parallel along the rows of word lines. A first pass transistor and a plurality of Y-pass transistors are coupled between the sense amplifier and the memory array. Second and third pass transistors are coupled between the dummy sense amplifier and the dummy bit-line. A plurality of N-channel MOS transistors are used to clamp all of the bit-lines ih the array and dummy bit-line to a ground potential. The operational sense amplifier is responsive to the sense amplifier, dummy sense amplifier and the clamping transistors for generating an output signal which has a fast response time when making a low-to-high transition (that is when selecting an unprogrammed memory cell).

High frequency, wide band, superlinear integrable amplifier and its method of fabrication

Abstract: An integrable, high frequency superlinear amplifier and its fabrication method is disclosed which is related to the basic amplifier fabrication field having negative feedback and signal conversion. The three stage amplifier design involves a first and second stage which have a narrow bandwidth response and a third amplifier stage with a larger or wider bandwidth response. The bandwidth of the wide bandwidth stage is such that when the gain curve for the two narrow bandwidth stages passes through the -6dB point at a first frequency then the peak point of the wide bandwidth stage is located at a second frequency higher than the first frequency. The wide bandwidth stage utilizes a single capacitor so that the resulting curve of the three stages has an approximately flat portion below the zero gain point. The impedance of the network is adjusted to a desired value through a feedback configuration.

Lower hybrid current drive in the presence of a DC electric field

Abstract: A code for numerical modelling of lower hybrid current drive has been developed which takes into account the DC electric field. The model is based on the Fokker-Planck equation, the plasma circuit equation and the power balance equations. The flow of power supplied by the RF waves and the OH coil (transformer) is investigated. Also studied are the current drive efficiency and the ramp-up efficiency, which is the ratio of RF energy to plasma electromagnetic energy. The ramp-up rate of the plasma current is slower and the RF power required for recharging the OH coil is higher when the DC electric field is taken into account than when it is neglected. The simulation results agree well with the results of Alcator C experiments. The RF energy and the time for ramp-up and recharge required for the next-generation tokamak are estimated.

Integrated circuit rf amplifier module

Abstract: A four-terminal integrated circuit high-frequency RF amplifier connects to external circuitry via a ground terminal, an RF input terminal, an RF output terminal and a DC biasing terminal. A two stage amplification architecture is employed - a current gain transistor (common-emitter) is cascoded with a subsequent voltage gain transistor (common-base) while yet maintaining RF signal inversion overall from input to output so as to increase stability. A biasing current-mirror transistor provides biasing current to the current-gain transistor. A fourth transistor connected as a forward-biased collector-base shorted diode between the current mirror biasing transistor and a common external biasing terminal supplies bias current to the current-mirror biasing transistor while simultaneously minimizing voltage swings across the current-gain transistor. The amplifier module has very low input capacitance which does not change appreciably with changes in load impedance, and operates with great stability under a wide range of different input and output conditions and RF frequencies. Because of its relative simplicity and compactness, the amplifier can be used to great advantage as an IC "building block" in a variety of different applications.

High Performance Monolithic Power Amplifier Using a Unique Ion Implantation Process

Abstract: State-of-the-art X-band power FETs and monolithic amplifiers have been fabricated by a high yield planar process using a unique double-peaked implant profile. A 1-mm FET has achieved 40 percent power added efficiency with 720 mW output power and 6.3 dB gain at 10 GHz. A two-stage monolithic amplifier has delivered 2.2 W output power at 9.5 GHz for a record 0.6 W/mm power density. The monolithic amplifier chips have also achieved 20 percent dc-yield and 5 percent uniformity in /sup I/DSS and /sup V/PO.