Showing papers on "RF power amplifier published in 2006"

A Generalized Memory Polynomial Model for Digital Predistortion of RF Power Amplifiers

Abstract: Conventional radio-frequency (RF) power amplifiers operating with wideband signals, such as wideband code-division multiple access (WCDMA) in the Universal Mobile Telecommunications System (UMTS) must be backed off considerably from their peak power level in order to control out-of-band spurious emissions, also known as "spectral regrowth." Adapting these amplifiers to wideband operation therefore entails larger size and higher cost than would otherwise be required for the same power output. An alternative solution, which is gaining widespread popularity, is to employ digital baseband predistortion ahead of the amplifier to compensate for the nonlinearity effects, hence allowing it to run closer to its maximum output power while maintaining low spectral regrowth. Recent improvements to the technique have included memory effects in the predistortion model, which are essential as the bandwidth increases. In this paper, we relate the general Volterra representation to the classical Wiener, Hammerstein, Wiener-Hammerstein, and parallel Wiener structures, and go on to describe some state-of-the-art predistortion models based on memory polynomials. We then propose a new generalized memory polynomial that achieves the best performance to date, as demonstrated herein with experimental results obtained from a testbed using an actual 30-W, 2-GHz power amplifier

RF Power Amplifiers for Wireless Communications, Second Edition (Artech House Microwave Library (Hardcover))

Abstract: This extensively revised edition of the bestselling Artech House book, RF Power Amplifiers for Wireless Communications, offers you a comprehensive, practical, and up-to-date understanding of how to tackle a power amplifier design with confidence and quickly determine the cause of malfunctioning hardware. Among the numerous updates, the Second Edition includes five new chapters on class AB PAs at GHz frequencies; switching PA modes at GHz frequencies; signals, modulation systems, and PA nonlinearities; power amplifier bias circuit design; and load-pull techniques. Chapters on efficiency enhancement methods and Class F design have been substantially extended, and many more practical examples and design tools are included on the accompanying CD-ROM. Supported with nearly 200 illustrations, the book contains the most complete survey of RF PA efficiency enhancement and linearization techniques in a single volume. It helps you design suitable matching networks which provide correct fundamental harmonic terminations for conventional (AB, B) high efficiency PA modes, understand the Class D, E, and F modes and their feasibility at microwave frequencies, and use envelope simulation techniques to analyze the effects of distortion in overdriven PAs. You learn how to maintain high efficiency operation at low points in an amplitude modulated signal envelope, including detailed coverage of the Doherty, Chireix, and Kahn techniques. Moreover, this authoritative resource helps you understand the possibilities and limitations of linearization methods, and offers guidance in objectively analyzing PA stability and oscillation problems.

A 950-MHz rectifier circuit for sensor network tags with 10-m distance

Abstract: This paper presents a 950-MHz wireless power transmission system and a high-sensitivity rectifier circuit for ubiquitous sensor network tags. The wireless power transmission offers a battery-life-free sensor tag by recharging the output power of a base station into a secondary battery implemented with the tag. For realizing the system, a high-sensitivity rectifier with dynamic gate-drain biasing has been developed in a 0.3-/spl mu/m CMOS process. The measurement results show that the proposed rectifier can recharge a 1.2-V secondary battery over -14-dBm input RF power at a power conversion efficiency of 1.2%. In the proposed wireless system, this sensitivity corresponds to 10-m distance communication at 4-W output power from a base station.

Dynamic Deviation Reduction-Based Volterra Behavioral Modeling of RF Power Amplifiers

Abstract: A new representation of the Volterra series is proposed, which is derived from a previously introduced modified Volterra series, but adapted to the discrete time domain and reformulated in a novel way. Based on this representation, an efficient model-pruning approach, called dynamic deviation reduction, is introduced to simplify the structure of Volterra-series-based RF power amplifier behavioral models aimed at significantly reducing the complexity of the model, but without incurring loss of model fidelity. Both static nonlinearities and different orders of dynamic behavior can be separately identified and the proposed representation retains the important property of linearity with respect to series coefficients. This model can, therefore, be easily extracted directly from the measured time domain of input and output samples of an amplifier by employing simple linear system identification algorithms. A systematic mathematical derivation is presented, together with validation of the proposed method using both computer simulation and experiment

An Improved Power-Added Efficiency 19-dBm Hybrid Envelope Elimination and Restoration Power Amplifier for 802.11g WLAN Applications

Abstract: A comparison of envelope elimination and restoration (EER) and envelope tracking (ET) is discussed and a "hybrid" wideband EER power amplifier (PA) for the WLAN 802.11g system is proposed. A 60% efficiency (the output envelope signal power/input dc power) DC-20-MHz wideband envelope amplifier is designed for wideband EER and wideband ET (WBET) applications. A design method is developed to optimize the efficiency of the envelope amplifier for a given peak-to-average ratio and average slew rate of the envelope signal. An experimental "hybrid" Class-E EER system shows an overall efficiency (modulated RF output power/envelope amplifier dc input power) of 36% and power-added efficiency (the modulated RF output power/envelope amplifier dc input power plus RF input power) of 28% for a WLAN 802.11g signal at 19-dBm (80 mW) output power at 2.4 GHz. Digital predistortion, time alignment, and memory effect mitigation are implemented. The measured 3% error vector magnitude exceeds the 802.11g specification for 5% for a 54-Mb/s modulation signal

High-Efficiency Envelope-Tracking W-CDMA Base-Station Amplifier Using GaN HFETs

Abstract: A high-efficiency wideband code-division multiple-access (W-CDMA) base-station amplifier is presented using high-performance GaN heterostructure field-effect transistors to achieve high gain and efficiency with good linearity For high efficiency, class J/E operation was employed, which can attain up to 80% efficiency over a wide range of input powers and power supply voltages For nonconstant envelope input, the average efficiency is further increased by employing the envelope-tracking architecture using a wide-bandwidth high-efficiency envelope amplifier The linearity of overall system is enhanced by digital pre-distortion The measured average power-added efficiency of the amplifier is as high as 507% for a W-CDMA modulated signal with peak-to-average power ratio of 767 dB at an average output power of 372 W and gain of 100 dB We believe that this corresponds to the best efficiency performance among reported base-station power amplifiers for W-CDMA The measured error vector magnitude is as low as 174% with adjacent channel leakage ratio of -510 dBc at an offset frequency of 5 MHz

Method, apparatus and system for power transmission

Abstract: A transmitter for transmitting power to a receiver to power a load, where the receiver does not have a DC-DC converter. The transmitter comprises a pulse generator for producing pulses of power. The transmitter comprises an antenna in communication with the pulse generator through which the pulses are transmitted from the transmitter. A system for power transmission which transmits only pulses of power without any data. A method for transmitting power to a receiver to power a load. An apparatus for transmitting power to a receiver to power a load comprises a plurality of transmitters, each of which produce pulses of power which are received by the receiver to power the load. A system for power transmission which receives pulses of power transmitted by the power transmitter to power a load but does not use the pulses as a clock signal.

The Doherty power amplifier

Abstract: In this article, we show that the Doherty amplifier is capable of delivering the stringent requirements of the base station power amplifiers. We explain the operation principles, including both linearity and efficiency improvements, and the basic circuit configuration of the amplifier. Advanced design methods to operate across wide bandwidth and improve the linearity are also described. For verification, the Doherty amplifier is implemented using laterally diffused metal oxide semiconductor (LDMOS) transistors and measured using a WCDMA 4FA signal. These results show that the Doherty amplifier is a promising candidate for base station power amplifiers with wide bandwidth, high efficiency, and linearity

A system and method for contact free transfer of power

Abstract: A system and method is provided for the inductive transfer of electric power between a substantially flat primary surface and a multitude of secondary devices in such a way that the power transfer is localized to the vicinities of individual device coils. The contact free power transfer does not require precise physical alignment between the primary surface and the secondary device and can allow the secondary device or devices to be placed anywhere and in arbitrary orientation with respect to the primary surface. Such power transfer is realized without the need of complex high frequency power switching network to turn the individual primary coils on or off and is completely scalable to almost arbitrary size. The local anti-resonance architecture of the primary device will block primary current from flowing when no secondary device or devices are in proximity to the local RF power network. The presence of a tuned secondary device detunes the local anti-resonance on the primary surface; thereby enable the RF power to be transferred from the local primary coils to the secondary device. The uniformity of the inductive coupling between the active primary surface and the secondary devices is improved with a novel multi-pole driving technique which produces an apparent traveling wave pattern across the primary surface.

Adaptive Multi-Band Multi-Mode Power Amplifier Using Integrated Varactor-Based Tunable Matching Networks

Abstract: This paper presents a multi-band multi-mode class-AB power amplifier, which utilizes continuously tunable input and output matching networks integrated in a low-loss silicon-on-glass technology. The tunable matching networks make use of very high Q varactor diodes (Q>100 @ 2 GHz) in a low distortion anti-series configuration to achieve the desired source and load impedance tunability. A QUBIC4G (SiGe, ft=50 GHz) high voltage breakdown transistor (VCBO=14 V, VCEO>3.6 V) is used as active device. The realized adaptive amplifier provides 13 dB gain, 27-28 dBm output power at the 900, 1800, 1900 and 2100 MHz bands. For the communication bands above 1 GHz optimum load adaptation is facilitated resulting in efficiencies between 30%-55% over a 10 dB output power control range. The total chip area (including matching networks) of the amplifier is 8 mm2

Apparatus and method for using ambient RF power in a portable terminal

Abstract: An apparatus and method for using ambient RF power in a portable terminal are provided. In the charging apparatus, an antenna array receives RF signals left derelict in the air, a rectifier rectifies the RF signals to DC voltages, and a power storage stores the DC voltages as power.

Power transmission system, apparatus and method with communication

Abstract: A power transmission system with communication having a base station having a wireless power transmitter a wireless data transmission component and a wireless data reception component. The system includes a remote station having a power harvester for converting the power from the power transmitter into direct current and a power storage component in communication with the power harvester for storing the direct current. Alternatively, the system includes a base station having a wireless power transmitter which transmits power at a frequency at which any sidebands are at or below a desired level, and a wireless data communication component.

Class-d amplifier

Abstract: A class D amplifier includes: an amplifier that generates a digital signal for driving a load based on an input signal; an attenuator that attenuates the input signal according to an attenuation command signal; and a clip prevention controller that outputs the attenuation command signal to intermittently attenuate the input signal when the digital signal is brought into a clip state or a near-clip state.

Pulsed plasma etching method and apparatus

Abstract: A plasma etching method includes preparing in a reaction chamber a semiconductor substrate on which a material layer to be etched is provided; and injecting an etching gas into the reaction chamber, the etching gas being ionized through an RF (Radio Frequency) power source to generate a plasma, wherein the RF power source outputs RF power in a pulse output mode. The plasma etching apparatus includes a reaction chamber adapted to contain an etching gas; and an RF power source adapted to output RF power for excitation of the etching gas to generate plasma, wherein the apparatus further include a pulse control circuit adapted to control the RF power source to output RF power in a pulse output mode. With the invention, the plasma for etching can be generated in a pulse output mode, thus improving a precision of an endpoint where the etching can be disabled.

RF Class-D Amplification With Bandpass Sigma–Delta Modulator Drive Signals

Abstract: The power efficiency of a RF Class-D amplifier with a bandpass sigma-delta (SigmaDeltaM) modulator is analyzed for a complementary voltage-switched configuration. The modulator broadens the application of the amplifier to include signals with time varying envelopes such as W-CDMA. The addition of a modulator introduces new design variables which affect amplifier power efficiency including coding efficiency and the average transition frequency of the pulse train. Design equations are derived for the optimum load impedance, output power, conduction losses, capacitive switching losses, and drain efficiency. The general design equations are consistent with both periodic and aperiodic drive signals. Analytic and simulated results are compared for an example design with pseudomorphic high-electron mobility transistor and metal-semiconductor field-effect transistor switches with a fourth-order bandpass SigmaDeltaM. The results show a drain efficiency of 52% with a 10-dB peak-to-average power ratio W-CDMA source signal at a frequency of 500 MHz

Band Separation and Efficiency Optimization in Linear-Assisted Switching Power Amplifiers

Abstract: Linear-assisted switching power amplifiers are based on combinations of switching converters (for high efficiency) and linear amplifiers (for high-speed, wide bandwidth responses) in applications such as envelope tracking for RF power amplifiers in polar modulation architectures, or audio amplifiers. This paper describes an approach to band separation and filter design to maximize the system efficiency and achieve near-ideal, wide-bandwidth responses. An experimental prototype is described, including a synchronous buck converter in combination with a class-AB linear amplifier. Experimental results for square wave and rectified sinusoid input signals demonstrate high bandwidth and high efficiency of the linear-assisted switching power amplifiers with optimized band separation.

A Low-Power RF Direct-Conversion Receiver/Transmitter for 2.4-GHz-Band IEEE 802.15.4 Standard in 0.18- $\mu{\hbox {m}}$ CMOS Technology

Abstract: This paper presents a low-power RF receiver/transmitter front-end for 2.4-GHz-band IEEE 802.15.4 standard in 0.18-mum CMOS technology. An RF receiver comprises a single-ended low-noise amplifier, a quadrature passive mixer, and a transimpedance amplifier. A current-mode passive mixer showing a very good 1/f noise performance is adopted to convert an RF signal directly to a baseband signal. Moreover, this type of passive mixer shows high-linearity performance, leading to overall RF receiver linearity improvement. A low-power, high-linearity transmitter front-end is implemented by using a passive mixer and two-stage driver amplifier in which the first stage is a conventional cascode amplifier and the second stage uses a folded cascode one. The receiver front-end achieves 30-dB voltage conversion gain, 7.3-dB noise figure with 1/f noise corner frequency of 70 kHz, -8-dBm input third-order intercept point, and +40-dBm input second-order intercept point. The transmitter front-end shows 12-dB power conversion gain, 0-dBm output power with 10-dBm output third-order intercept point, and -30-dB local-oscillator suppression. The receiver and transmitter front-end dissipate 3.5 and 3 mA from a 1.8-V supply, respectively

A capacitive RF power sensor based on MEMS technology

Abstract: Wideband 100 kHz–4 GHz power sensors are presented, which are based on sensing the electrostatic force between an RF signal line and a suspended membrane. The electrostatic force, which is proportional to the square of the rms signal voltage and thus to the signal power, results in a displacement of the suspended membrane. This displacement is detected capacitively, allowing the sensing of the signal power with extremely low dissipative losses; therefore the sensor can be placed in a transmission line with negligible disturbance of the signal. Devices have been designed and fabricated successfully by aluminum surface micromachining using photoresist as the sacrificial layer. Optimization of the design with SONNET has resulted in measured return and insertion losses (S11 and S21) better than -30 dB and -0.15 dB, respectively, up to 4 GHz, and a sensitivity of 90 aF mW-1.

A GaN HEMT Class F Amplifier at 2 GHz with > 80 % PAE

Abstract: A Class F amplifier has been designed, fabricated, and tested using a GaN HEMT transistor and hybrid printed circuit board (PCB) packaging. The amplifier has a peak power-added efficiency (PAE) of 85% with an output power of 16.5 W. A gate-connected field-plated and a source-connected field-plated device of the same size and layout were measured in this topology. An output power and drain efficiency tradeoff, dependant on the drain impedance at the fundamental frequency due to the on-state resistance, is explored. A comparison between Class F and Inverse F, given particular operating conditions for this device, is made.

Variable bandwidth envelope modulator for use with envelope elimination and restoration transmitter architecture and method

Abstract: A RF transmitter has at least one amplifier having an input terminal for receiving a phase modulated signal to be transmitted on an RF carrier and an input node for receiving a modulation signal for amplitude modulating the RF carrier. The RF transmitter further includes an amplitude modulator having an output coupled to the input node of the power amplifier through a low-pass filter. The low-pass filter includes at least one variable filter component for varying a bandwidth of the low-pass filter. In a preferred embodiment an envelope elimination and restoration (EER) RF transmitter includes at least one power RF amplifier having the input terminal for receiving the phase modulated signal to be transmitted on the RF carrier, and further including an input power node for receiving a modulated voltage for amplitude modulating the RF `carrier. The EER RF transmitter further includes a class-S modulator having a variable bandwidth low-pass filter having an output coupled to the input power node and including at least one first variable capacitance.

High frequency power amplifier circuit and radio communication system

Abstract: There is provided a high frequency power amplifier circuit capable of enhancing detection accuracy of an output level, necessary for feedback control of the high frequency power amplifier circuit, and capable of executing output power control with higher precision, With the high frequency power amplifier circuit, the detection of the output level, necessary for feedback control of the high frequency power amplifier circuit is executed by use of a current detection method, and in an electronic device comprising a differential amplifier for comparing an output power detection signal with an output level designation signal and for generating a signal for controlling a gain of the high frequency power amplifier circuit according to a potential difference between the two signals, a power source voltage with variation less than that for the power source voltage of the high frequency power amplifier circuit is used as the operational power source voltage of the output power detection circuit. Further, there is provided a capacitor across which an AC component is taken out from the output side of a power amplification transistor in the final amplification stage of the high frequency power amplifier circuit to be thereby impressed to the interior of the output power detection circuit.

Method and system for transmitter envelope delay calibration

Abstract: A test signal comprising periodic waveform, such as a triangular waveform and sawtooth waveform, is used for propagation delay matching in a transceiver front-end. The test signal is separately fed to the envelope path and the RF path. At the power amplifier stage, a phase modulator is used to obtain the envelope signal and the phase modulated RF signal for demodulation by an IQ demodulator. At the output end of the IQ demodulator, the I-signal is measured while the delay block is adjusted in order to vary the propagation delay. When the propagation delay matching is correct, the peak-to-peak value of the I-signal is a minimum. Preferably, during calibration using the test signal, the transmitter RF power amplifier is disabled so that no spurious signals will be sent. The transmitter can be an EDGE polar transmitter, a non-EDGE transmitter or a EER polar transmitter.

Arc detection and handling in radio frequency power applications

Abstract: A radio frequency power delivery system comprises an RF power generator, arc detection circuitry, and control logic responsive to the arc detection circuitry. A dynamic boundary is computed about the measured value of a parameter representative of or related to the power transferred from the power generator to a load. A subsequently measured value of the parameter that exceeds the computed dynamic boundary of the parameter indicates detection of an arc. Upon detection of an arc, power delivery from the generator is interrupted or adjusted, or other action is taken, until the arc is extinguished. By employing dynamic computation of arc detection boundaries, the invention allows for arc handling in RF power deliver systems regardless of whether the system has reached a stable power delivery condition.

High efficiency class-F RF/microwave power amplifiers

Abstract: This article provides a tutorial and review of recent developments in high-efficiency class F RF/ microwave PAs. The principles of class-F RF PAs are explained first. Recent progress in their theory and in design techniques is then presented. Different approaches of class-F PA designs are explained, and some examples of practical designs are illustrated. Finally, an attempt is made to discuss the future developments of class-F RF/microwave PAs.

Rf transmitter with compensation of differential path delay

Abstract: A transmitter has a power amplifier (40) to amplify an input signal having amplitude modulation, a supply voltage controller (10) to control a supply voltage of the power amplifier (40) according to the envelope, a sensor (R1) for sensing a modulation of a current drawn by the power amplifier (40), a delay detector (20) for detecting a delay of the controlled supply voltage relative to the sensed current, and a delay adjuster (30) for compensating the relative delay according to the detected delay. By sensing a current drawn, the delay detected can include any delay contributed by the power amplifier (40) up to that point, and yet avoid the more complex circuitry needed to derive the delay from an output of the power amplifier. Thus the distortion and out of band emissions caused by differential delays can be reduced more effectively.

A digitally controlled DC/DC converter for an RF power amplifier

Abstract: This paper describes design and implementation of a digitally controlled dc/dc converter that provides a dynamically adjustable supply voltage for a radio frequency power amplifier (RFPA). The techniques employed in the design include a combination of constant-frequency continuous conduction mode (CCM) and a variable-frequency discontinuous conduction mode to achieve very high converter efficiency over a wide range of output power levels. The variable-frequency converter control is accomplished using a current-estimator circuit, which eliminates the need for current sensing. A field-programmable gate array (FPGA)-based digital controller implementation allows programmability of the mode transition and other controller parameters. In the complete experimental system, which consists of the digitally controlled dc/dc converter and a class-E RFPA operating at 10GHz, experimental results show that the overall system efficiency is significantly improved over a wide range of RFPA output power levels.

Communication semiconductor integrated circuit, a wireless communication apparatus, and a loop gain calibration method

Abstract: A polar-loop wireless communication apparatus includes, on a forward path between an amplitude detector and a power amplifier which constitute an amplitude control loop, a variable gain amplifier and a switch to change characteristics of a loop filter to output a frequency bandwidth of the amplitude control loop to an order less than an order for normal operation. The system is operated with the characteristics set to the lower order to measure outputs from the power amplifier to calibrate the output power of the power transmitter, and the register is operated with the characteristics set to the higher order to measure the open loop gain of the amplitude control. According to results of the calculation, data to correct gain characteristics of the variable gain amplifier with respect to an output control signal is stored in a nonvolatile memory of a baseband circuit.

Superimposed training for OFDM: a peak-to-average power ratio analysis

Abstract: Orthogonal frequency division multiplexing (OFDM) transmission with superimposed training is considered in this paper. One major disadvantage of OFDM is the significant amplitude fluctuations, i.e., high peak-to-average power ratios (PARs). High PARs require large backoff of the average operating power of a radio-frequency (RF) power amplifier (PA) in order to linearly amplify the signal, thus reducing the dc to RF power conversion efficiency. The PAR of the OFDM signal is examined with superimposed training, and its complementary cumulative distribution function (CCDF) is derived. Achievable lower and upper bounds on the CCDF are also determined. In addition, the PAR change is linked to the effective signal-to-noise ratio (SNR) and thus the bit-error-rate (BER) performance under the fixed dc power constraint. Simulation results are presented to illustrate the proposed PAR and power analysis for OFDM with superimposed training.

A C-band high-efficiency second-harmonic-tuned hybrid power amplifier in GaN technology

Abstract: In this paper, the design, fabrication, and test of high-efficiency, high-power C-band harmonic-tuned power amplifiers in GaN technology is reported. The amplifier has been designed utilizing second-harmonic tuning for high-efficiency operation, thus exploiting the high-breakdown voltage peculiarity of GaN-based devices. Realized in a hybrid form, the amplifier has been characterized in terms of small-signal, power, and intermodulation (IMD) performance. An operating bandwidth over 20% around 5.5 GHz, with 33-dBm minimum output power, and 60% drain efficiency at center frequency is demonstrated, together with low IMD