Showing papers on "RF power amplifier published in 2003"

An electrosurgical generator

Abstract: An electrosurgical generator for supplying RF power to an electrosurgical instrument for cutting or vaporising tissue has an RF output stage (42) with an RF power bridge (Q1, Q2, Q3, Q4), a pair of output lines (74) and a series-resonant output network (48). The output impedance of the output stage (42) at the output lines (74) is less than 200/√P ohms, where P is the maximum continuous RF output power of the generator. The generator offers improved cutting and vaporising performance, especially in relation to the reliability with which an arc can be struck when presented with an initial low impedance load. Overloading of the output stage is prevented by rapidly operating protection circuitry responsive to a predetermined electrical condition such as a substantial short-circuit across the output lines. In the preferred embodiment, the output stage is capable of maintaining output pulses at least 1kW peak by supplying the power bridge from a large reservoir capacitor (60). Pulsing is dynamically variable in response to load conditions by controlling the maximum energy per pulse in response to the reservoir capacitor voltage.

Behavioral modeling of nonlinear RF power amplifiers considering memory effects

Abstract: This paper proposes a new behavioral model to treat memory effects in nonlinear power amplifiers (PAs) Phenomena such as asymmetries in lower and upper intermodulation terms, and variation of AM/AM and AM/PM, depending on signal history, are often observed in high-power PAs To treat these phenomena, this paper presents a model based on the previously developed memory polynomial model The contribution made in this paper is to augment the memory polynomial model to include a sparse delay tap structure that reduces the parameter space required for accurate model identification A figure-of-merit, called the memory effect ratio, is defined to quantify the relative level of distortion due to memory effects, as compared to the memoryless portion Another figure-of-merit is defined as the memory effect modeling ratio, which quantifies the degree to which the PA memory effects have been accounted for in the model This new technique is validated using a variety of RF PAs, including an 880-MHz and a 21-GHz high-power laterally diffused metal-oxide semiconductor PA and various signals such as two-tone, eight-tone, and IS-95B signals

Distortion in RF power amplifiers

Abstract: Introduction Some Circuit Theory and Terminology Memory Effects in RF Power Amplifiers The Volterra Model Simulating and Measuring Memory Effects Cancellation of Memory Effects Characterization of the Volterra Model Appendix A: Volterra Analysis in More Detail Appendix B: IM3 Equations for Cascaded 2nd-Order Distortion Mechanisms Appendix C: The Truncation Error

Low-power, high-modulation-index amplifier for use in battery-powered device

Abstract: An external transmitter circuit drives an implantable neural stimulator having an implanted coil from a primary coil driven by a power amplifier. For efficient power consumption, the transmitter output circuit (which includes the primary coil driven by the power amplifier inductively coupled with the implanted coil) operates as a tuned resonant circuit. When operating as a tuned resonant circuit, it is difficult to modulate the carrier signal with data having sharp rise and fall times without using a high power modulation amplifier. Sharp rise and fall times are needed in order to ensure reliable data transmission. To overcome this difficulty, the present invention includes an output switch that selectively inserts a resistor in the transmitter output coil circuit in order to de-tune the resonant circuit only during those times when data modulation is needed. Such de-tuning allows sharp rise and fall times in the data modulation without the need for using a high power modulation amplifier. Because data modulation is typically needed for only a small percent of the time that a carrier signal is present, it is thus possible using the present invention to achieve reliable data modulation, transmission and reception without having to use a high power modulation amplifier in the transmitter.

A 2.4-GHz 0.18-/spl mu/m CMOS self-biased cascode power amplifier

Abstract: A two-stage self-biased cascode power amplifier in 0.18-/spl mu/m CMOS process for Class-1 Bluetooth application is presented. The power amplifier provides 23-dBm output power with a power-added efficiency (PAE) of 42% at 2.4 GHz. It has a small signal gain of 38 dB and a large signal gain of 31 dB at saturation. This is the highest gain reported for a two-stage design in CMOS at the 0.8-2.4-GHz frequency range. A novel self-biasing and bootstrapping technique is presented that relaxes the restriction due to hot carrier degradation in power amplifiers and alleviates the need to use thick-oxide transistors that have poor RF performance compared with the standard transistors available in the same process. The power amplifier shows no performance degradation after ten days of continuous operation under maximum output power at 2.4-V supply. It is demonstrated that a sliding bias technique can be used to both significantly improve the PAE at mid-power range and linearize the power amplifier. By using the sliding bias technique, the PAE at 16 dBm is increased from 6% to 19%, and the gain variation over the entire power range is reduced from 7 to 0.6 dB.

An integrated 200-W class-D audio amplifier

Abstract: An integrated stereo class-D audio power amplifier realized in a silicon-on-insulator (SOI)-based BCD technology is presented. The amplifier is capable of delivering 2/spl times/100 W in two 4-/spl Omega/ loads at a supply voltage of 60 V. A second-order feedback loop is used to suppress supply ripple and pulse-shape errors in the switching power stage. The limiting factor in the performance of any class-D amplifiers is the quality of the switching power stage. A high-speed low-current levelshifter and a robust deadtime control arrangement are proposed that enable the realization of a robust high-quality switching power stage. Some practical issues with respect to robustness and electromagnetic compatibility are discussed.

Plasma processing system

Abstract: A processing system (100) includes a processing chamber (120) having a substrate holder (130) and an electrode (125). The processing system includes a compression control system, a gas supplying system, and a monitor device (160). The electrode (125) is connected to a multi-frequency RF power supply (110) via a matching circuit (115) having a single variable element. The multi-frequency RF power supply is set to a first frequency so as to ignite plasma or set to a second frequency so as to sustain the plasma.

Method of correcting distortion in a power amplifier

Abstract: The invention is a method of correcting distortion in a power amplifier in a transmitter. The method includes applying an input time varying modulated data signal to the power amplifier which outputs an amplified time varying modulated data signal which is an amplification of the input time varying modulated data signal; storing samples of the input time varying modulated data signal; storing samples of the output amplified time varying data signal; using the stored input and output time varying modulated samples to provide a processor implemented model with parameters representing a non-linear characteristic of the power amplifier without the use of any polynomials; and producing predistortion coefficients.

Thermal memory effects modeling and compensation in RF power amplifiers and predistortion linearizers

Abstract: Memory effects, which influence the performance of RF power amplifiers (PAs) and predistortion-based linearizers, become more significant and critical in designing these circuits as the modulation signal bandwidth and operation power increase. This paper reports on an attempt to investigate, model, and quantify the contributions of the electrical nonlinearity effects and the thermal memory effects to a PA's distortion generation, as well as how to compensate for these effects in designing baseband predistortion schemes. The first part of this paper reports on the development of an accurate dynamic expression of the instantaneous junction temperature as a function of the instantaneous dissipated power. This expression has been used in the construction of an electrothermal model for the PA. Parameters for the new proposed behavior model were determined from the PA measurements obtained under different excitation conditions (e.g., small-signal and pulsed RF tests). This study led us to conclude that the effects of the transistor self-heating phenomenon are more important under narrow-band signal (e.g., enhanced data for global evolution of global system for mobile communications) than for signals with wide modulation bandwidth (CDMA2000, Universal Mobile Telecommunications System). In the second part of this paper, the newly developed model has also been used to design a temperature-compensated predistortion function to compensate for these effects. The linearized PA output spectrum and error vector magnitude show a significant performance improvement in the temperature-compensated predistortion function over a memoryless predistortion. The results of these measurements that have been conducted on a 90-W peak lateral double-diffused metal-oxide-semiconductor PA are in agreement with those obtained from simulations using the developed PA and the predistorter models implemented in an ADS environment.

Ultra-wide-band tellurite-based fiber Raman amplifier

Abstract: We describe the first wide-band tellurite-based fiber Raman amplifier (T-FRA) for application to seamless ultra-large-capacity dense wavelength-division multiplexing (WDM) systems. First, we confirmed that the Raman scattering characteristics of the tellurite-based fiber has so large a gain coefficient and Stokes shift that we can achieve a wide-band tellurite-based fiber Raman amplifier with a shorter fiber length than when using silica-based fiber. Second, we investigated the small signal gain and the signal transmission characteristics for a high gain and high output power operation with a single-stage amplifier. Focusing on double Rayleigh scattering, we compared the high gain limit of tellurite- and silica-based fibers. We then studied the impact of nonlinear effects by measuring the bit error rate (BER) when using a two-stage amplifier with a high output power of 18.8 dBm in which we simultaneously amplified eight channel signals in the L-band located on the ITU 100-GHz grid. Finally, we designed a wide-band tellurite-based fiber Raman amplifier with a multiwavelength band pumping scheme. We constructed this amplifier with a tellurite-based fiber only 250 m in length pumped by four-wavelength-channel laser diodes, and it provided a 160-nm bandwidth with a gain of over 10 dB and a noise figure below 10 dB from 1490 to 1650 nm. We also measured the BER to confirm the transmission characteristics of the amplifier for single channel operation over the whole signal wavelength range of 160 nm. We thus confirmed that the amplifier could be employed in ultra-high-capacity WDM systems.

System and method for antenna diversity using equal power joint maximal ratio combining

Abstract: An equal gain composite beamforming technique which constrains that the power of the signal output by each antenna is the same, and is equal to the total power of the transmit signal divided by the number N of transmit antennas from which the signal is to be transmitted. By reducing output power requirements for each power amplifier, the silicon area of the power amplifiers are reduced by as much as N times (where N is equal to the number of transmit antennas) relative to a non-equal gain CBF.

A microwave Doherty amplifier employing envelope tracking technique for high efficiency and linearity

Abstract: In this letter, we demonstrate a microwave Doherty amplifier employing an input signal envelope tracking technique. In the amplifier, the gate bias of the peaking amplifier is controlled according to the magnitude of the envelope. A 2.14-GHz Doherty amplifier is implemented using 4-W PEP LDMOSFETs, and an adaptive controlled gate bias circuit is constructed and the control shape is optimized experimentally. The performance of the microwave Doherty amplifier is compared with that of a class AB amplifier using one-tone, two-tone, and forward-link wideband code-division multiple access (WCDMA) signals. For a forward-link WCDMA signal, the measured power added efficiency (PAE) of the microwave Doherty amplifier is 39.4% at -30 dBc adjacent channel leakage ratio (ACLR), while that of the comparable class AB amplifier is 24.2% at the same ACLR level.

An efficient Volterra-based behavioral model for wideband RF power amplifiers

Abstract: Efficient and accurate behavioral modeling of RF power amplifiers with memory effects becomes of critical importance in the system-level analysis and design of wide band digital communication systems. In this paper, we present a novel Volterra-based behavioral model implemented through a bank of parallel FIR filters, the coefficients of which may be readily extracted from time-domain measurement or circuit envelope simulation. This model can reproduce the nonlinear distortion of power amplifiers with memory effects excited by wideband modulated signals with better accuracy compared to conventional quasi-memoryless models.

High linearity Doherty communication amplifier with bias control

Abstract: The present invention relates to bias control of a power amplification circuit of a mobile device for improving the efficiency and the linearity properties of the power amplifier. In one embodiment, the power amplifier improves these properties by receiving a voltage control signal to bias a supplemental amplifier so that the power amplifier operates in a Doherty mode in a low output power range and in a non-Doherty mode in a high output power range. In the non-Doherty mode, the supplemental amplifier is biased as a class AB amplifier via the received voltage control signal to satisfy the non-linear operational requirements of the power amplifier in the high output power range. The power amplifier generates the voltage control signal based upon power levels of signals received from a remote base station.

Method for tuning an envelope tracking amplification system

Abstract: An optimal operating point of an envelope tracking amplification system (100) that includes a radio frequency (RF) power amplifier (110) having an RF amplifying element (114) is determined based on an application to the RF power amplifier of a supply voltage (211) that is less than the rated voltage of the RF amplifying element.

Development of internal-antenna-driven large-area RF plasma sources using multiple low-inductance antenna units

Abstract: Large-area and high-density radio frequency (RF) plasmas at 13.56 MHz have been produced by inductive coupling of internal-type low-inductance antenna units. The present study has been carried out to develop the basic discharge techniques which can be applied to production of meter-scale large-area and/or large-volume plasma sources with high density for a variety of plasma processes. The plasma source could be operated stably to attain plasma density as high as 1×1012 cm−3 at argon pressures of approximately 1 Pa. It has been demonstrated that high plasma density can be obtained efficiently using the low-inductance internal antenna configuration with effectively suppressed electrostatic coupling. Discharge experiments in a meter-scale chamber demonstrated uniform plasma production with densities as high as 6×1011 cm−3 at an argon pressure of 1.3 Pa and a RF power of 4 kW.

Method and system for providing power management in a radio frequency power amplifier using adaptive envelope tracking

Abstract: A method for providing power management in a radio frequency power amplifier using adaptive envelope tracking is provided that includes receiving an input voltage. A power control signal is received. A feedback signal is received. An amplifier input signal is received. From the input voltage, a regulated power supply signal is generated based on the power control signal, the feedback signal, and the amplifier input signal.

Power amplifier circuit and method using bandlimited signal component estimates

Abstract: A power amplifier circuit for receiving a variable envelope input signal and for producing an amplified output signal is provided. The power amplifier circuit includes an envelope approximation circuit, an envelope amplifier circuit, a phasor approximation circuit, a quadrature modulation circuit, and a power amplifier. The envelope approximation circuit receives the variable envelope input signal and produces a bandlimited estimated envelope signal, corresponding to the amplitude of the variable envelope input signal. The bandlimited estimated envelope signal is then amplified by an envelope amplifier circuit. The amplified envelope signal is then coupled to the supply input of the power amplifer. The phasor approximation circuit receives the variable envelope input signal and produces a bandlimited estimated phasor signal. The quadrature modulation circuit receives the estimated phase signal and produces a modulated phase signal. The modulated phase signal is then coupled to the signal input of the power amplifier. The power amplifier then produces an amplified output signal.

Optimization of error loops in distributed power amplifiers

Abstract: Several feed-forward RF power amplifiers configured for use in a distributed array, each having a main amplifier within a carrier null loop and an error amplifier within an error loop. Each carrier null loop includes a switch configured to selectively disable the carrier null loop, thereby disabling the carrier null loop, and injecting an actual RF signal into the error loop allowing the error loop to be optimized using the actual RF signal.

Broad-band high-power amplifier using spatial power-combining technique

Abstract: High power, broad bandwidth, high linearity, and low noise are among the most important features in amplifier design. The broad-band spatial power-combining technique addresses all these issues by combining the output power of a large quantity of microwave monolithic integrated circuit (MMIC) amplifiers in a broad-band coaxial waveguide environment, while maintaining good linearity and improving phase noise of the MMIC amplifiers. A coaxial waveguide was used as the host of the combining circuits for broader bandwidth and better uniformity by equally distributing the input power to each element. A new compact coaxial combiner with much smaller size is investigated. Broad-band slotline to microstrip-line transition is integrated for better compatibility with commercial MMIC amplifiers. Thermal simulations are performed and an improved thermal management scheme over previous designs is employed to improve the heat sinking in high-power application. A high-power amplifier using the compact combiner design is built and demonstrated to have a bandwidth from 6 to 17 GHz with 44-W maximum output power. Linearity measurement has shown a high third-order intercept point of 52 dBm. Analysis shows the amplifier has the ability to extend spurious-free dynamic range by N/sup 2/3/ times. The amplifier also has shown a residual phase floor close to -140 dBc at 10-kHz offset from the carrier with 5-6-dB reductions compared to a single MMIC amplifier it integrates.

A dual-path bandwidth extension amplifier topology with dual-loop parallel compensation

Abstract: A dual-path amplifier topology with dual-loop parallel compensation technique is proposed for low-power three-stage amplifiers. By using two parallel high-speed paths for high-frequency signal propagation, there is no passive capacitive feedback network loaded at the amplifier output. Both the bandwidth and slew rate are thus significantly improved. Implemented in a 0.6-/spl mu/m CMOS process, the proposed three-stage amplifier has over 100-dB gain, 7-MHz gain-bandwidth product, and 3.3-V//spl mu/s average slew rate while only dissipating 330 /spl mu/W at 1.5 V, when driving a 25-k/spl Omega///120-pF load. The proposed amplifier achieves at least two times improvement in bandwidth-to-power and slew-rate-to-power efficiencies than all other reported multistage amplifiers using different compensation topologies.

Monolithic supply modulated RF power amplifier and DC-DC power converter IC

Abstract: Mobile communication systems require highly efficient, linear, and integrated power amplifiers. This paper reports the results of a monolithic envelope following system implemented in a 0.18 /spl mu/m SiGe BiCMOS process technology. The monolithic envelope following system consists of a synchronous buck DC-DC converter, which is integrated with and provides the power supply for a 900 MHz power amplifier while tracking the envelope of the RF input signal.

Radio frequency power detecting circuit and method therefor

Abstract: A circuit for detecting the amount of radio frequency power provided by an amplifier. The circuit contains an array of coupled transistors in two power amplifiers, and a log-detector circuit, all resident on a single semiconductor die. The main power amplifier contains the larger array of transistors to amplify the radio frequency signal for feeding to an antenna, and a secondary power amplifier contains a smaller array of transistors to provide a scaled output that is proportional to the amplified radio frequency signal and is used to control the main power amplifier. The log-detector circuit converts the signal from the secondary power amplifier to a full-wave rectified log-linear DC signal that is logarithmically proportional to the controlling signal. The DC signal output from the log-detector circuit is fed to the main power amp to control it.

Development of Backward Wave Oscillators for Terahertz Applications

Abstract: Calabazas Creek Research, Inc. is funded by the National Aeronautics and Space Administration to develop advanced backward wave oscillators that incorporate energy recovery, air cooling and improved performance. An improved coupler transforms the generated RF power to a high-purity, Gaussian output mode. The construction of a 600-700 GHz BWO is currently underway with higher frequency sources in development. Simulations predict 6-8 mW of RF power over a 100 GHz bandwidth.

Signal amplifier using a doherty amplifier

Abstract: A signal amplifier includes a splitter for splitting an input signal into first and second signals, first and second bias control networks for generating a base bias signal for a Doherty amplifier in accordance with a power level of the input signal, a carrier amplifier for amplifying the first input signal, a peaking amplifier for amplifying the second input signal and a Doherty output network for combining the amplified signals. Through a simplified transformation of characteristic impedances in the Doherty output network, minimization of circuitry including the signal amplifier is obtained. Further, by controlling the Doherty amplifier in accordance with the power level of the input signal, both high efficiency and high linearity of the signal amplifier are achieved.

Radio transmitters with temperature compensated power control profiles and methods of operating same

Abstract: A radio transmitter includes a power control table, a power amplifier, and a power controller. The power control table includes a plurality of control values. The power amplifier amplifies an RF signal for transmission with an adjustable gain. The power controller adjusts the gain of the power amplifier based on the power control table and a temperature signal that is indicative of a temperature of at least a portion of the radio transmitter.

Integrated antennas on Si with over 100 GHz performance, fabricated using an optimized proton implantation process

Abstract: We have improved the performance of integrated antennas on Si for possible application in wireless communications and wireless interconnects. For practical VLSI integration, we have reduced the antenna size and optimized the proton implantation to a low energy of /spl sim/4 MeV with a depth of /spl sim/175 /spl mu/m. To avoid any possible contamination, the ion implantation is applied after device fabrication. Excellent performance such as very low RF power loss up to 50 GHz, record high 103 GHz antenna resonance, and sharp 5 GHz bandwidth have been achieved.