Showing papers on "RF power amplifier published in 2002"

Power amplifiers and transmitters for RF and microwave

Abstract: The generation of RF/microwave power is required not only in wireless communications, but also in applications such as jamming, imaging, RF heating, and miniature dc/dc converters. Each application has its own unique requirements for frequency, bandwidth, load, power, efficiency, linearity, and cost. RF power is generated by a wide variety of techniques, implementations, and active devices. Power amplifiers are incorporated into transmitters in a similarly wide variety of architectures, including linear, Kalm, envelope tracking, outphasing, and Doherty. Linearity can be improved through techniques such as feedback, feedforward, and predistortion.

RF power amplifiers for wireless communications

Abstract: A wide variety of semiconductor devices are used in wireless power amplifiers. The RF performance and other attributes of cellphone RF power amplifiers using Si and GaAs based technologies are reviewed and compared.

Advanced Techniques in RF Power Amplifier Design

Abstract: RF power amplifier modes Doherty and Chireix - themes and variations topics in PA non-linearity envelope feedback predistortion feedforward microwave-power amplifier design.

Fully integrated CMOS power amplifier design using the distributed active-transformer architecture

Abstract: A novel on-chip impedance matching and power-combining method, the distributed active transformer is presented. It combines several low-voltage push-pull amplifiers efficiently with their outputs in series to produce a larger output power while maintaining a 50-/spl Omega/ match. It also uses virtual ac grounds and magnetic couplings extensively to eliminate the need for any off-chip component, such as tuned bonding wires or external inductors. Furthermore, it desensitizes the operation of the amplifier to the inductance of bonding wires making the design more reproducible. To demonstrate the feasibility of this concept, a 2.4-GHz 2-W 2-V truly fully integrated power amplifier with 50-/spl Omega/ input and output matching has been fabricated using 0.35-/spl mu/m CMOS transistors. It achieves a power added efficiency (PAE) of 41 % at this power level. It can also produce 450 mW using a 1-V supply. Harmonic suppression is 64 dBc or better. This new topology makes possible a truly fully integrated watt-level gigahertz range low-voltage CMOS power amplifier for the first time.

High-power femtosecond Yb-doped fiber amplifier.

Abstract: We report on the generation of linearly chirped parabolic pulses with 17-W average power at 75 MHz repetition rate and diffraction-limited beam quality in a large-mode-area ytterbium-doped fiber amplifier. Highly efficient transmission gratings in fused silica are applied to recompress these pulses down to 80-fs with an efficiency of 60%, resulting in a peak power of 1.7 MW. Power scaling limitations given by the amplifier bandwidth are discussed.

Quantifying memory effects in RF power amplifiers

Abstract: This paper proposes a system-level behavioral model for RF power amplifiers (PAs), which exhibit memory effects, that is based on the parallel Wiener system. The model extraction is performed using two-tone intermodulation distortion (IMD) measurements with different tone frequency spacings and power levels. It is found that by using such a model, more accurate adjacent-channel power-ratio levels may be predicted for high PAS close to the carrier frequency. This is validated using IS-95B CDMA signals on a low-power (0.5 W) class-AB PA, and on a high-power (45 W) class-B PA. The model also provides a means to quantify memory effects in terms of a figure-of-merit that calculates the relative contribution to the IMD of the memoryless and memory portion of the PA nonlinearity. This figure-of-merit is useful in providing an estimate of the amount of correction that a memoryless predistortion system may have on PAS that exhibit memory effects.

Method and apparatus for VHF plasma processing with load mismatch reliability and stability

Abstract: A radio frequency (RF) generator apparatus for a plasma processing system that is resistant to nonlinear load mismatch conditions is provided. The apparatus includes an RF oscillator configured to generate an RF signal, an RF amplifier responsive to the RF signal to produce a VHF RF signal having sufficient power to drive a plasma chamber load, and a VHF-band circulator coupled to the amplifier and configured to isolate nonlinearities of the plasma chamber load from the amplifier.

PCS/W-CDMA dual-band MMIC power amplifier with a newly proposed linearizing bias circuit

Abstract: A personal communications service/wide-band code division multiple access (PCS/W-CDMA) dual-band monolithic microwave integrated circuit (MMIC) power amplifier with a single-chip MMIC and a single-path output matching network is demonstrated by adopting a newly proposed on-chip linearizer. The linearizer is composed of the base-emitter diode of an active bias transistor and a capacitor to provide an RF short at the base node of the active bias transistor. The linearizer enhances the linearity of the power amplifier effectively for both PCS and W-CDMA bands with no additional DC power consumption, and has negligible insertion power loss with almost no increase in die area. It improves the input 1-dB gain compression point by 18.5 (20) dB and phase distortion by 6.1/spl deg/ (12.42/spl deg/) at an output power of 28 (28) dBm for the PCS (W-CDMA) band while keeping the base bias voltage of the power amplifier as designed. A PCS and W-CDMA dual-band InGaP heterojunction bipolar transistor MMIC power amplifier with single input and output and no switch for band selection is embodied by implementing the linearizer and by designing the amplifier to have broad-band characteristics. The dual-band power amplifier exhibits an output power of 30 (28.5) dBm, power-added efficiency of 39.5 % (36 %), and adjacent channel power ratio of -46 (-50) dBc at the output power of 28 (28) dBm under 3.4-V operation voltage for PCS (W-CDMA) applications.

Digital signal processor enhanced pulse width modulation amplifier

Abstract: A pulse width modulator (PWM) audio power amplifier (10) with a switch mode power converter (206) is provided that may adjust the duty of the switch mode power converter (206) based on output current. The PWM audio power amplifier (10) may include a digital signal processor (18) to process an input signal and control the switch mode power converter (206) to minimize distortion in an amplified output signal. The control within the PWM audio power amplifier (10) may include digital feed forward open loop control or may combine digital feed forward open loop control with analog negative feedback closed loop control to minimize distortion in the output signal.

Class E with parallel circuit - a new challenge for high-efficiency RF and microwave power amplifiers

Abstract: In this paper, a new circuit configuration of switched-mode tuned Class E power amplifiers with load network consisting of a parallel capacitance, a parallel inductance and a series resonant circuit tuned on the fundamental is defined using a detailed analytical description with a complete set of the design equations. The ideal collector voltage and current waveforms demonstrate a possibility of 100-percent efficiency. The circuit schematic of a parallel-circuit Class E power amplifier can be realized with lumped or transmission-line elements. Two examples of high power LDMOSFET and low-voltage HBT power amplifiers, utilizing a parallel-circuit Class E circuit configuration, are presented.

Apparatus and method for radio frequency de-coupling and bias voltage control in a plasma reactor

Abstract: Provided is a method and apparatus for controlling a bias voltage over a wide range and for de-coupling dual radio frequency (RF) currents to allow for independent control of plasma density and ion energy of a plasma for processing a substrate. An exemplary apparatus provides a plasma processing chamber which includes a bottom electrode configured to hold a substrate and first and second RF power supplies being connected to the bottom electrode. Also included is a top electrode which is electrically isolated from a top ground extension. A filter array defining a set of filter settings is included. A switch is coupled to the top electrode and the switch is configured to interconnect the top electrode to one of the filter settings. The filter settings are configured to enable or disable RF current generated from one or both of the RF power supplies from passing through the top electrode.

A 700-MHz 1-W fully differential CMOS class-E power amplifier

Abstract: A 700-MHz fully differential class-E CMOS power amplifier for wireless applications has been built toward maximum efficiency The prototype can deliver 1 W of output power in a 50-/spl Omega/ output impedance The maximum power-added efficiency (PAE) is measured to be 62% The obtained efficiency and output power is compared with the class-E amplifiers theory

Multi-wavelength light amplifier

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second-stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Composite power amplifier

Abstract: A PAMELA-type of composite power amplifier is configured in such a way that a single power amplifier is operated at low output voltage amplitudes by prohibiting a pair of outphasing power amplifiers to produce any current. Preferably, at output voltage amplitudes above the maximum voltage of the single power amplifier is to be reached, the pair of outphasing power amplifiers is taken into operation providing currents phase shifted by substantially 180 degrees. When also the outphasing power amplifiers reach their maximum voltages, an outphasing operation is performed.

Analysis of power recycling techniques for RF and microwave outphasing power amplifiers

Abstract: A power recycling technique has been analyzed for efficiency-enhanced radio-frequency (RF) and microwave outphasing power amplifiers for mobile wireless communications. By use of a simple power recycling network, a considerable portion of the wasted power can be recovered back to the power supply, and the enhancement of the overall power efficiency can be achieved without sacrificing the high-linearity performance of the amplifier system. An analysis and calculations have been conducted to optimize the recycling network for maximum power efficiency. The results predict a significant improvement on the overall power efficiency of the amplifier system for various modulations.

Low bias current/temperature compensation current mirror for linear power amplifier

Abstract: A power amplifier circuit whose performance is optimized by operating its stages in substantially close to a Class B mode by reducing quiescent current during low driver signal levels As the driver signal amplitude increases, the operation of the amplifier is configured to dynamically adjust to be in a Class AB mode, thereby increasing the power efficiency of the overall circuit at kiw drive levels A further enhancement to the power amplifier circuit includes a temperature compensation circuit to adjust the bias of the amplifier so as to stabilize the performance in a wide temperature range

Resonant frequency tracking system and method for use in a radio frequency (RF) power supply

Abstract: An RF power supply that is capable of tracking rapid changes in the resonant frequency of a load and capable of quickly responding to varying load conditions so as to deliver the desired amount of power. The present invention also provides an RF power supply capable of delivering a wide range of power over a broad frequency range to a load that is remotely located from the power supply. According to one embodiment, the RF power supply includes a direct current (DC) voltage source that provides a DC voltage within a predetermined voltage range; an amplifier, coupled to the DC voltage source, that provides an alternating voltage to a tank circuit connected to an output of the RF power supply; a frequency controller, coupled to the amplifier, to set the frequency of the alternating voltage produced by the amplifier; and a sensor, coupled to the load, to provide a signal to the frequency controller, where the frequency controller sets the frequency of the alternating voltage based on the signal received from the sensor.

A method and system for broadband predistortion linearizaion

Abstract: The invention relates to a method and system for broadband digital predistortion linearizaion, which used to overcome the influence of memory effect in the radio frequency power amplifier, to expand the digital predistortion linearizaion bandwidth, and to improve the digital predistortion linearizaion performance. The method and system, according to characteristic parameter of amplifier, can get the in band and out of band predistortion signal, and then the combined signals be inputted to power amplifier as input signal; A part of the output signal from the power amplifier can be the feedback signal, compare it to the original input signal, and according to the comparative result, characteristic parameter of amplifier of in band and out of band pedistortion signal be generated by adaptive adjustment, so that the waveforms or frequency spectrum of feedback signal and input original signal could be nearest.

Rf power amplifier circuit

Abstract: A RF power amplifier circuit has at least one power transistor and a protection circuit protecting the power transistor against high voltages that lead to a destructive breakdown of the transistor. The circuit comprises a power transistor (2), a biasing circuit (6) biasing the power transistor; a peak detector (8) measuring the output voltage of the power transistor; and a comparator circuit (12) connected to the peak detector (8) and designed to reduce the base current of the power transistor (2) when controlled by the peak detector (8).

Continuous radio–frequency tuning of an optoelectronic oscillator with dispersive feedback

Abstract: We describe and demonstrate a novel technique for continuously tuning the frequency of a dual-loop-configuration optoelectronic rf oscillator. The rf tunability is obtained from a tunable diode laser and dispersive optical fibers. Results are presented for three ranges of frequency, centered at 550 MHz, 3 GHz, and 9 GHz. The frequency can be tuned electrically with constant rf power within a range of 0.1-1.9 MHz, depending on the center oscillation frequency. The tuning range can be increased eightfold through the use of highly dispersive fibers.

Measurement and Simulation of the Energy Consumption of a WLAN Interface

Abstract: The energy efficiency of a wireless network interface is a major design issue since mobile devices are often constrained by the battery. The work presented here follows the question which parameter of a WLAN interface can be adjusted to improve energy efficiency.We measured the power consumption of a WLAN interface for various operational modes and parameter settings for a non-impaired Radio Frequency (RF) channel and derived the energy consumed to transmit one bit of payload. The power consumption values were used to parameterize a simulation model of the WLAN interface which was in turn used to investigate the influence of parameters like RF power level, packet size, and data rate on the energy efficiency in case the radio channel becomes worse. Additionally, an analytical energy consumption model for a simple case is presented. Our results indicate, that control of the RF power level and data rate adaption have the highest impact on the energy efficiency.

Waveforms for envelope tracking transmitter

Abstract: A method and device for improving the efficiency of an envelope tracking transmitter in which a power amplifier for coupling modulated signals in a carrier frequency to an antenna for transmission. The transmitter comprises a power supply for providing a supply voltage to the power amplifier, and a computation means for providing a waveform indicative of the envelope of the modulated signal to the power supply in order to modify the supply voltage. A lower limit is imposed to the waveform so that the supply voltage to the power supply is always greater than a predetermined value. Moreover, when information is transmitted in times slots which are started and ended by ramp periods, a constant signal, based on the root-mean-square value of the waveform, is used to modify the waveform so that the supply voltage to the power amplifier includes a constant voltage level in the ramp periods.

Lumped and distributed lattice-type LC-baluns

Abstract: This paper presents two balun circuits derived from the lumped Lattice-type LC-balun. First the lumped LC-balun bridge elements are substituted by microstrip lines. This results in an improved performance at the 2nd and 3rd harmonic frequency for RF power amplifier output baluns. Secondly, the lumped Lattice-type LC-balun is extended to a dual band balun. Independent impedance transformation and balun conversion can be done at two different frequencies. The design equations are derived.

Efficiency improvement techniques at low power levels for linear CDMA and WCDMA power amplifiers

Abstract: Power amplifiers are significant contributors to current consumption within mobile phones resulting in continued focus on design techniques to improve power amplifier efficiency. The techniques presented here use variable bias current and supply voltage, which allow enhanced efficiency at low power levels, and variable load impedance, which provides tradeoffs for optimum linearity and efficiency as a function of power level and battery voltage.

Balanced power amplifier with a bypass structure

Abstract: A balanced power amplifier circuit arrangement comprises a driver amplifier stage (22) adapted to receive and amplify a signal. The amplified signal is input to a first coupler (26). The first coupler (26) produces an in-phase signal and an out-of-phase quadrature signal. A first power amplifier (38) receives and amplifies the in-phase signal. A second power amplifier (40) receives and amplifies the out-of-phase signal. A first switch (28) alternately connects an isolated port of the first coupler to ground (32) or a bypass path (36). A second coupler (42) receives and combines the amplified in-phase signal and the amplified out-of-phase signal to produce a combined signal. A second switch (30) alternately connects an isolated port of the second coupler (42) to either ground (34) or the bypass path (36). When the power amplifiers (38, 40) are powered down, the first coupler (26) splits the RF-signal into an in-phase signal and an out-of-phase signal. The power amplifiers (38, 40) appear as reflective impedances to the signal when they are powered down. Each signal reflects off the first and second power amplifiers (38, 40), respectively. The first coupler (26) combines the reflected signals and routes the combined signal through the bypass path (36) to the second coupler (42). The second coupler (42) splits the signal into an in-phase and out-of-phase signal and routes each to the power amplifiers (38, 40). The power amplifiers (38, 40) reflect each signal back to the second coupler (42). The second coupler (42) combines the signals and routes the combined signal to the RF-output port. The circuit arrangement enables the integration of the balanced amplifier and first and second couplers (26, 42) into a single power amplifier package to provide low power bypassing without the need of an external circulator component.

Realistic power-amplifiers characterization with application to baseband digital predistortion for 3G base stations

Abstract: In this paper, a realistic, accurate, versatile, and thermal-free complex behavior test bed suitable for third-generation power-amplifiers characterization is proposed. Using this approach, a 90-W peak power amplifier based on Motorola-LDMOS class-AB transistors was measured under several signal excitations such as W-CDMA, cdma2000, and eight-tone signals. The results obtained show noticeable discrepancies compared to those measured using a vector network analyzer (HP-8510C) for both AM/AM and AM/PM curves. This test bed was also used for the investigation of the memory effect in RF power amplifiers. In the second part of this paper, the characterization results obtained by the test bed were used to design a digital predistorter for an LDMOS amplifier. A baseband predistortion accurate synthesis algorithm is presented. Indeed, a memoryless baseband digital predistorter lookup table was directly synthesized using the measured AM/AM and AM/PM curves without any need to perform additional analytical derivations and/or numerical optimizations. The predistorter synthesis procedure requires only one iteration, contrary to previous works, which need several iterations to obtain similar performances.

Power amplifier configuration

Abstract: A variable capacitance and control system used in a compensative manner to improve efficiency in power amplifier arrangements arranged to receive a power input which is voltage-modulated responsive to at least one control signal representative of the data signal. Also included are methods and software for controlling said power amplifier arrangements including the variable capacitance and control system. The data input to the power amplifier is pre-distorted and the resulting power amplification is substantially linear. The arrangement may be used in wireless base station transmitters, for example. Improved data transmission services are also provided which make use of such power amplifiers.

Direct digital polar modulator

Abstract: A polar modulator creates an amplitude signal and a frequency signal and digitally adjusts the signals so that the frequency and amplitude signals arrive at the power amplifier at the appropriate times. A digital predistortion filter is applied to the frequency signal. The frequency signal is then provided to a single port of a fractional N divider in a phase locked loop. The output of the phase locked loop drives an input of the power amplifier while the amplitude signal is converted to an analog signal and controls the power supply input of the power amplifier.

RF power handling of capacitive RF MEMS devices

Abstract: RF MEMS switches provide a low-cost, high-performance solution to many RF/microwave applications. In this paper, progress in characterizing capacitive MEMS devices under high RF power is presented. The switches tested demonstrated power handling capabilities of 510 mW for continuous RF power and 4 W for pulsed RF power. In addition, the reliability of these switches was tested at various power levels indicating that under continuous RF power, the lifetime is not affected until the 510 mW power level is reached. Once a power failure is observed, it is completely recoverable by lowering the RF power level below the threshold point. A description of the power failures and their associated operating conditions is presented.