Showing papers on "RF power amplifier published in 2000"

High-Linearity RF Amplifier Design

Abstract: From the Publisher: Based on the author's real-world design experience in this key emerging area, this is the first single comprehensive guide to examine and directly compare all major RF power amplifier linearization techniques in detail. Packed with practical tips, more than 250 illustrations, and over 600 verified equations, the book saves you valuable design time while helping you avoid costly design errors. It covers the modeling and measurement of amplifier non-linearity, and describes the main methods for overcoming non-linearity in a wide range of applications, including: > base stations using feedforward and predistortion > mobile communications systems and handsets using RF or digital predistortion, cartesian loop, LINC and envelope elimination and restoration (EE&R ) > satellite systems using any of these techniques

Electric and surgical signal generator

Abstract: PROBLEM TO BE SOLVED: To attain safe usage by reducing or stopping radio frequency power to be added on a generator output from a power source in accordance with the prescribed condition of the signal of a monitor which indicates the change of reflection power caused by means of the change of a tissue state under a medical treatment. SOLUTION: The generator 10 is provided with a radio frequency source having a frequency generating source 12 and a power amplifier 14 and an oscillation frequency in the generation source 12 is controlled by a control system 16. Power for electric surgery is supplied to an electrode assembly 24 having a medical electrode by a UHF band with an impedance isolator 18 such as a circulator in accordance with the output of the amplifier 14, an opposite direction power output 23A is derived from a directional coupler 23 and the output 23A is inputted to a detection and signal adjusting stage 29. Then the point of time when change occurs in tissue is decided so that the power output of the generator is reduced or stopped by the control system 16 by the decision result.

High efficiency CDMA RF power amplifier using dynamic envelope tracking technique

Abstract: This work describes a 2-W peak-envelope linear power amplifier based upon the envelope tracking (ET) technique with application to CDMA cellular radio handsets. Both drain voltages of a two stage monolithic GaAs IC are varied with respect to the long term rms value of the modulated signal using a high efficiency Class-S modulator. The modulator is implemented as a single chip silicon IC to supply currents in excess of 1 A. The RF amplifier IC utilizes two AlGaAs/InGaAs heterostructure insulated-gate FET structures which allows single voltage supply operation with state-of-the-art linearity and efficiency performance. When driven by a CDMA O-QPSK signal, the ET amplifier exhibits desired spectral linearity while achieving a remarkable 5/spl times/ improvement in overall efficiency, compared to fixed supply bias, when measured in a reverse link urban based mobile transmitter power profile.

High-gain wide-band gyrotron traveling wave amplifier with a helically corrugated waveguide

Abstract: First bandwidth measurements of a novel gyrotron amplifier are presented The coupling between the second harmonic cyclotron mode of a gyrating electron beam and the radiation field occurred in the region of near infinite phase velocity over a broad bandwidth by using a cylindrical waveguide with a helical corrugation on its internal surface With a beam energy of 185 keV, the amplifier achieved a maximum output power of 11 MW, saturated gain of 37 dB, linear gain of 47 dB, saturated bandwidth of 84 to 104 GHz ( $21%$ relative bandwidth), and an efficiency of $29%$, in good agreement with theory

Integrated superconducting receivers

Abstract: The concept of a fully superconducting integrated receiver is developed and experimentally tested. This single-chip sub-mm wave receiver includes a planar antenna integrated with a SIS mixer and an internal superconducting Josephson-type local oscillator (flux-flow oscillator, FFO). The receiver is tested with a DSB noise temperature below 100 K around 500 GHz being pumped by its internal local oscillator (LO). The instantaneous bandwidth of 15-20% is estimated via FTS and heterodyne measurements that meet the requirements of most practical applications. The far field antenna beam is measured as ≈f/10 with sidelobes below -16 dB that is suitable for coupling to a real telescope antenna. A nine-pixel imaging array receiver with each pixel containing an internally pumped receiver chip is developed and tested. A linewidth of the phase locked FFO as low as 1 Hz is measured relative to a reference oscillator in the frequency range 270-440 GHz. An rf amplifier on the base of a dc SQUID is developed and tested showing a noise figure below 10 K at 4 GHz and a bandwidth of about 300 MHz. This amplifier can be included as a part of an integrated receiver that is valuable for array applications.

RF transmitter with extended efficient power control range

Abstract: A highly efficient radio frequency (RF) transmitter provides both wide bandwidth and an extended power control range. The RF transmitter includes stage switching, bias adjustment, and drain supply modulation. These components are used to provide fine and coarse power control and EER envelope fluctuations. The RF transmitter is useful in wireless communications to increase both handset talk time and battery life.

A new linearization technique for MOSFET RF amplifier using multiple gated transistors

Abstract: A simple linearization technique using multiple gated common source transistors is proposed where gate width and gate drive (V/sub gs/-V/sub th/) of each transistor are chosen to compensate for the nonlinear characteristics of the main transistor. To demonstrate the feasibility of this approach, a prototype double-gated RF amplifier using two MOSFETs is implemented and its RF characteristics are compared with those of a single one. The results show that, compared with a conventional single-gate transistor amplifier, the third order intermodulation (IMD/sub 3/) is improved by 6 dB with similar gain, fundamental output power, and DC power consumption. Because the auxiliary transistor is smaller than the main one and biased at subthreshold, adding this does not affect amplifier characteristics appreciably other than the nonlinearity. With further optimization using multiple gated transistors, much better nonlinear performance per power consumption would be expected.

Electronically tuned power amplifier

Abstract: A circuit and method for electronically tuning an RF power amplifier. The output filter includes at least one electronically variable reactance. The electronically tuned power amplifier may be tuned rapidly to a selected frequency, to a selected impedance, or to produce a selected output amplitude. An optional controller translates frequency, impedance, or modulation inputs into tuning signals. High-efficiency, wideband amplitude modulation is produced by varying the amplifier load impedance along preferred loci.

Buck or boost power converter

Abstract: A buck or boost (BOB) power converter circuit. A buck converter is cascaded with a boost converter to form a buck or boost circuit ( 20 ). The BOB converter is controlled by a controller ( 26 ) such that only the buck or boost converter is operating at any given time. A reference signal V ref can be applied to the controller ( 26 ) such that the output voltage from the converter closely tracks the reference signal. Positive and negative ramp signals are generated and an error feedback signal is compared with the ramp signals to control the output in accord with V ref . This is useful in application of the output voltage as the power supply to an RF Power Amplifier ( 16 ) so that the reference signal can represent the envelope of a signal to be transmitted and the RF PA ( 16 ) can operate at high efficiency.

LINC power amplifier combiner method efficiency optimization

Abstract: Linear amplification using nonlinear components (LINC) is a method of vector summing two constant amplitude phase-modulated signals to achieve power amplification. The theoretical efficiency of the LINC power amplifier has been reported as 100% since highly efficient nonlinear constant amplitude amplifiers can be used. However, the 100% efficiency performance is only possible at one or two loads along the power output curve. The bulk of the papers regarding LINC has focused on clever implementations of the signal vector decomposition as well as methods to achieve highly linear signal separation. There has been little regard in the literature to the signal combiner implementation necessary to achieve the high power-added efficiency (PAE) of the LINC radio frequency (RF) power amplifier. Efficiency is not an intrinsic property of the combiner implementations, however, the combiner method is the single biggest contributor to efficient performance of a LINC RF power amplifier. This paper develops an analysis method that determines the efficiency of the LINC power amplifier as a function of the amplitude modulation statistics. This can be employed to design the RF communication system amplitude modulation characteristics and to tradeoff and optimize the RF transmitter PAE.

Analog predistortion linearizer for high-power RF amplifiers

Abstract: We have developed an analog predistortion linearizer for a high-power amplifier of a code-division multiple-access (CDMA) base station. To effectively suppress the spectral regrowth in the adjacent channels, the odd-order intermodulation distortions (IMDs) should be cancelled. To accomplish this purpose, we employed a predistorter, which can cancel the third and fifth IMDs independently. The implemented predistorter linearized the RF amplifier with an average power of 45 dBm at 2.37-2.4-GHz band. A 9-dB suppression of spectral regrowth, from 33 to 42 dBc, was achieved for the CDMA signal with an 8.192-Mc/s chip rate over a 30-MHz bandwidth.

Analysis and design of power efficient class D amplifier output stages

Abstract: A Class D amplifier comprises a pulse width modulator and an output stage. In this paper we analyze the power dissipation mechanisms and derive the overall power efficiency of the output stage realized using the finger and waffle layouts. We compare the relative merits of these layouts; we propose two design methodologies to determine the aspect ratios of the transistors in the output stage for optimum power efficiency (optimum for a given fabrication process, supply voltage and load resistance): (1) optimization to a single modulation index point and (2) optimization to a range of modulation indexes. For the design of an output stage with optimum power efficiency (and small IC area), we recommend optimization to a range of modulation indexes and a layout realized by the waffle structure. The theoretical analysis and derivations are verified on the basis of computer simulations and measurements on fabricated prototype ICs.

Use of antiphase signals for predistortion training within an amplifier system

Abstract: A LINC amplifier of a radio frequency transmitter provides substantially linear amplification from two nonlinear amplifiers by decomposing the original signal into two constant amplitude envelope, phase varying signals, which, when combined, constructively and destructively interfere to re-form the original signal. The output of the LINC amplifier, which is to be transmitted via an antenna, is an amplified form of the original signal. The LINC amplifier uses a digital control mechanism to control and adapt a digital compensation network that directly compensates for the imperfections of the analog RF environment, including the amplifiers. The mechanism monitors the combined amplifier output and adjusts the signal components in order to precisely compensate for any differences in the characteristics of the separate signal paths which would cause the combination not to accurately represent the original signal. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

Circuit design technique for high efficiency Class F amplifiers

Abstract: In this paper, lead network circuit technique to design high efficiency Class F amplifiers using new types of loading circuits was demonstrated. The loading circuits were realized using both lumped elements and transmission lines. The derived values of each circuit element are given. The simulation procedure and experimental verification were performed on the example of high-voltage LDMOSFET power amplifier. The test measurements show that, for this power amplifier, 76% drain efficiency can be achieved for 20 W output power at 500 MHz operating frequency.

Apparatus and method for geostatistical analysis of wireless signal propagation

Abstract: A method utilizing statistical interpolation techniques to analyze and simulate the spatial variability and continuity of radio frequency data collected from a wireless cellular system. The method is used for cellular system planning and management. After installation and setup of cellular base stations, further analysis and refinement of RF data is implemented to determine signal coverage of the tower, locations of RF holes in system, reuse of frequencies, and overlapping RF signals between two or more towers causing interference. The method analyzes raw RF power data that is collected by drive testing a sample of roads in a cellular system. A geostatistical model of the RF propagation at a cellular system is determined through kriging. The RF path loss trend estimation is extracted from each the raw data and modeled to describe data variability across the entire cellular system area. An estimated path loss signal map is then prepared for any area of interest within a cellular system.

Wide bandgap semiconductor transistors for microwave power amplifiers

Abstract: Explores the RF power performance of microwave amplifiers fabricated from wide bandgap semiconductor transistors and demonstrates that microwave power amplifiers fabricated from 4H-SiC and AlGaN/GaN transistors offer superior RF power performance, particularly at elevated temperatures. Theoretical models predict room temperature RF output power on the order of 4-6 W/mm and 10-12 W/mm, with power-added efficiency (PAE) approaching the ideal values for class A and B operation, available from 4H-SiC MESFETs and AlGaN/GaN HFETs, respectively. All calculations were thoroughly calibrated against dc and RF experimental data. The simulations indicate operation at elevated temperature at least up to 5000/spl deg/C is possible. The RF output power capability of these devices compares very favorably with the 1 W/mm available from GaAs MESFETs. The wide bandgap semiconductor devices will find application in power amplifiers for base station transmitters for wireless telephone systems, HDTV transmitters, power modules for phased-array radars, and other applications. The devices are particularly attractive for applications that require operation at elevated temperature.

Analog predistortion linearizer for high power rf amplifier

Abstract: Analog predistortion linearizer for the high power amplifier of CDMA base station has been developed. To suppress the spectral regrowth in the adjacent channel effectively, the odd order intermodulation distortions should be cancelled. For the purpose, the predistorter, which can cancel the 3rd and 5th intermodulation distortions independently, has been employed. The implemented pre-distorter linearized the RF amplifier with average power 45 dBm at 2.37-2.4 GHz band. 9 dB suppression of spectral regrowth was achieved for CDMA signal over 30 MHz bandwidth.

Class-E switching-mode high-efficiency tuned RF/microwave power amplifier: improved design equations

Abstract: Improved accuracy design equations for Class-E switching-mode high-efficiency tuned RF/microwave power amplifiers are presented.

Plasma processing apparatus

Abstract: In a plasma etching apparatus, a process gas is supplied into a process chamber and converted into plasma by means of RF discharge, and a semiconductor wafer placed on a lower electrode is etched by the plasma. An RF power supply mechanism is connected to the lower electrode for applying thereto a superposed RF power for forming an RF electric field in the process chamber. The RF power supply mechanism has first and second RF power supplies for respectively oscillating a low frequency RF component and a high frequency RF component having a higher frequency than the low frequency RF component. The high frequency RF component from the second frequency RF component supply has its wave form modulated by a modulator on the basis of the wave form of the low frequency RF component from the first frequency RF power supply. Thereafter, the modulated high frequency RF component and the low frequency RF component are superposed upon each other. The high frequency RF component has a larger amplitude at a negative side peak of the low frequency RF component than at a positive side peak of the low frequency RF component.

Two-tone IMD asymmetry in microwave power amplifiers

Abstract: This paper presents the first study of the relation between the IMD asymmetries, often observed in almost all power amplifiers subject to a two-tone test, and the nonlinear characteristics of their active devices. First, the reasons for the different amplitudes of the two adjacent tones are investigated using a general circuit with frequency dependent embedding impedances, and resistive and reactive nonlinearities. Those theoretical conclusions are then extrapolated for real circuits, and validated by comparing results obtained from nonlinear simulation to laboratory measurements of a microwave power amplifier.

Distortion detection apparatus for controlling predistortion, carrier cancellation and feed-forward cancellation in linear rf power amplifiers

Abstract: RF power amplifier distortion can be accurately measured in the presence of multi-carrier input signals, by using a common swept local oscillator to tune RF input and output receivers, whose outputs are monitored for distortion correction purposes. In carrier cancellation and feedforward cancellation mode, when the power detected by the input receiver exceeds a power threshold, the processor accumulates a digital representation of uncancelled carrier energy detected by the output receiver when sampling the signal at the output of the carrier cancellation combiner. It otherwise accumulates uncancelled IMD sampled at the output of the amplifier downstream of the feedforward cancellation coupler. In predistortion mode, the output receiver monitors only the output of the carrier cancellation combiner. When the power detected by the input receiver does not exceed the carrier power threshold, any energy measured by the output receiver corresponds to residual distortion energy from the predistorted main amplifier. This allows predistortion to be adaptively controlled by minimizing accumulated energy detected by the output receiver when it monitors the output of the carrier cancellation combiner during the entire sweep.

Bandpass delta-sigma class-S amplifier

Abstract: A class-S amplifier with a bandpass delta-sigma modulated input is demonstrated using CMOS devices at 10 MHz. With a two-tone modulated input, third-order intermodulation products below –40 dBc were measured, with an output power of 26 dBm and a drain efficiency of 33%. This new amplifier topology demonstrates promising performance for simultaneously achieving high linearity and efficiency.

Tuning analysis for the high-Q class-E power amplifier

Abstract: The effects of component variations on a high-Q class-E amplifier are simulated and measured. Design equations are provided for the case of a 50% duty cycle with B at its optimum value for a given R. Six distinct operating points are analyzed for the output network. The problem of tuning a high-Q class-E amplifier is addressed. Normally, it cannot be tuned for maximum output power without degrading efficiency. An auxiliary circuit is added to the design so that it can be tuned for maximum output power in order to achieve optimum efficiency. Measured data are obtained at low frequencies for an amplifier with a loaded Q of 340.

A 3.2-V operation single-chip dual-band AlGaAs/GaAs HBT MMIC power amplifier with active feedback circuit technique

Abstract: This paper describes the design and experimental results for a 3.2-V operation single-chip AlGaAs/GaAs heterojunction bipolar transistor (HBT) monolithic microwave integrated circuit (IMMIC) power amplifier for GSM900 and DCS1800 dual-band applications. The following two new circuit techniques are proposed for implementing the power amplifier. One is an on-chip HBT bias switch which in turn switches the amplifier between 900 and 1800 MHz. The proposed switch configuration allows the switch using a high turn-on voltage of 1.3 V of AlGaAs/GaAs HBT's to operate with a 3-V low supply voltage, because the switch circuitry needs no stacked configuration. The other is an active feedback circuit (AFB) to prevent permanent failure of HBT's in the output power stage even under severe conditions of oversupply voltage and strongly mismatching load. Experimental results revealed that the proposed feedback circuit, which works as a voltage limiter, can protect the output stage HBT's from an excessive collector voltage swing even when the amplifier is operated under a condition of a 5-V oversupply voltage and a 10:1 voltage standing-wave ratio (VSWR) mismatching load. Under a normal condition of 3.2 V and a 50-/spl Omega/ matching load, the IC is capable of delivering an output power of 34.5 dBm and a power-added efficiency (PaE) of 52% in a GSM900 mode, and a 32-dBm output power and a 32% PAE in a DCS1800 mode.

Baseband RF voltage-current probe

Abstract: An RF probe for a plasma chamber picks up current and voltage samples of the RF power applied to an RF plasma chamber, and the RF voltage and current waveforms are supplied to respective mixers. A local oscillator supplies both mixers with a local oscillator signal at the RF frequency plus or minus about 15 KHz, so that the mixers provide respective voltage and current baseband signals that are frequency shifted down to the audio range. The phase relation to the applied current and voltage is preserved in the baseband signals. These baseband signals are then applied to a stereo, two-channel A/D converter, which provides a serial digital signal to a digital signal processor or DSP. A local oscillator interface brings a feedback signal from the DSP to the local oscillator. The DSP can be suitably programmed to obtain complex Fast Fourier Transforms of the voltage and current baseband samples. The frequency-domain spectra are analyzed to obtain, with great accuracy, magnitude of voltage and current and phase angle. Other parameters are derived from these three.

High efficiency low-voltage power amplifier design by second-harmonic manipulation

Abstract: The effect of second-harmonic loading on power amplifiers operated with a low-voltage supply is investigated. Closed-form expressions and design formulas are derived, making use of a simplified device model. The correctness of the assumptions and the validity range of the derived expressions is then verified by means of a full nonlinear analysis method and model: sample low-voltage designs for a power stage are performed, demonstrating the potentials of the proposed methodology. ©2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 19–32, 2000.

Analysis and experimental waveform study on inverse class class-F mode of microwave power FETs

Abstract: The new inverse class F operation mode for high-efficiency power amplifiers is analyzed. Unlike regular class F, it requires an open circuit termination at the second harmonic and a small impedance termination at the third harmonic. The inverse class F features higher PAE than class F but requires transistors with higher breakdown voltages. A study performed using the waveform measurement technique in conjunction with the active/passive load-pull system showed PAE=83% for the inverse class F compared to PAE=64% for the class F. The measured results are in good agreement with the analytical prediction.

Amplifier system with a discrete Raman fiber amplifier module

Abstract: An amplifier system includes: (i) a distributed Raman fiber amplifier adapted to amplify C and L -band signals and; (ii) a discrete Raman fiber amplifier module that includes a C-band amplification stage and an L-band amplification stage. The discrete Raman fiber amplifier module is operatively connected to the distributed Raman fiber amplifier and amplifies signals received from the distributed Raman fiber amplifier. In one embodiment the distributed Raman fiber amplifier and the discrete Raman fiber amplifier share optical pump power provided by the shared pump.

Driving circuits for switch mode RF power amplifiers

Abstract: The present invention, generally speaking, provides an RF amplifier circuit architecture that enables high efficiency to be achieved while avoiding complicated matching networks and load networks The active device may be of the bipolar transistor type or the FET (field effect transistor) type A simple driving circuit is provided for each type of active device In accordance with one embodiment of the invention, a single-ended switch mode RF amplifier includes an RF input signal; an active device having a control terminal; and a non-resonant driving circuit for receiving the RF input signal and controlling a signal applied to the control terminal so as to operate the active device in switch mode

Smart amplifier for time division duplex wireless applications

Abstract: A bi-directional antenna-mount amplifier particularly suited to be compatible with a broad range of advanced spread spectrum TDD wireless applications relying on either direct sequence or frequency hopping, at a wide range of frequencies, and which allows the radio device sharing of an associated antenna in different time intervals, where signal distortion is minimized due to operation of the amplifier which is governed by an equation and associated gain control circuits to maintain constant output power and prevent transmit signal saturation.