High Efficiency Power Amplifier Design Research Articles

High efficiency and high linearity power amplifier design

The optimum high-frequency Class-F loading conditions are inferred, accounting for the effects of actual output device behavior, and deriving useful charts for an effective design. The important ro...

High efficiency and high linearity power amplifier design

The optimum high-frequency Class-F loading conditions are inferred, account- ing for the effects of actual output device behavior, and deriving useful charts for an effective design. The important role of the biasing point selection is stressed, demonstrating that it must be different from the Class-B theoretical one to get the expected improvement. The IMD behavior of the Class-F amplifier is presented and the large-signal sweet-spot origin in the IMD output characteristics is discussed, together with possible strategies to improve inter- modulation distortion performances. The control of the sweet spot position is demonstrated via proper terminating impedances, both at fundamental and harmonic frequencies and low

Accurate simulation models yield high-efficiency power amplifier design

The design of RF and microwave power amplifiers continues to be somewhat of an art yet to be reduced to a systematic repeatable design practice on a wide-scale basis, despite the many excellent treatments of the subject in the literature and a number of courses. The general unavailability of sufficiently accurate and reliable nonlinear models for power transistors has been a major factor in limiting the accuracy of power amplifier (PA) simulation results. Suitable nonlinear models must properly treat the nonlinear and combined dc/ac analysis required for proper power compression and efficiency simulation under varied load and bias conditions. In this article, an accurate nonlinear transistor model is shown to form the basis for a systematic simulation-based design procedure for a microwave PA.

Nonlinear approaches to the design of microwave power amplifiers

Commonly used approaches for the design of power amplifiers (PAs), specifically in the microwave and millimeter-wave frequency range, are reviewed and discussed. Measurement-based techniques are compared with CAD-based approaches, stressing their relative strengths and weaknesses. Simplified techniques are also discussed, particularly addressing the preliminary evaluation of the power capabilities of a given device and to gather physical insight into the power-generating mechanisms. Finally, harmonic tuning for high-efficiency power amplifier design is outlined, together with its basic application rules. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 493–506, 2004.

An Approach to Harmonic Load– and Source–Pull Measurements for High-Efficiency PA Design

High-efficiency power-amplifier design requires numerous efforts to investigate both input and output harmonic terminations effects. A simplified theoretical approach to clarify the relevance of such terminations is presented here, and design criteria to improve efficiency for high-frequency applications are briefly discussed. An advanced active load/source-pull test-bench has been used to validate theoretical harmonic tuning techniques, characterizing an active device. The adopted optimization strategy is presented, together with measured results obtained with a medium-power 1-mm MESFET at 1 GHz. Input second harmonic impedances effects are stressed, showing a drain efficiency spread between 37%-49% for a fixed input power level, corresponding to 1-dB compression. Finally, as predicted by the presented theory, after input second harmonic tuning, further improvements are obtained, increasing fundamental output load resistive part, demonstrating an additional drain efficiency enhancement, which reaches a level of 55% at 1-dB compression.

Theoretical facet and experimental results of harmonic tuned PAs

High-efficiency power amplifier design criteria imply a synthesis of input and output networks with particular emphasis on their harmonic behavior. In this article, a simplified approach to clarify the relevance of such terminations is presented. Starting from the implications of power balance for stage performance, design criteria to improve the efficiency of high-frequency applications are presented. In order to validate the approach, comparisons among the performances of single-stage amplifiers, all operated at 5 GHz under a sinusoidal driving signal and synthesized by utilizing different design methodologies, are presented. Drain efficiencies at 1-dB compression of 44.5%, 53.3%, and 61.56% have been measured respectively for the tuned load and harmonically manipulated (2nd and 2nd & 3rd) realized amplifiers, compared with a simulated drain efficiency of 55% using the Class E approach. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 459–472, 2003.

High-efficiency push-pull power amplifier integrated with quasi-Yagi antenna

This paper presents a C-band push-pull power amplifier integrated with a modified uniplanar quasi-Yagi antenna. In this circuit, corrugation is added to the truncated ground plane of the antenna so that it can be used for both out-of-phase power combining and second harmonic tuning. By using the active integrated antenna concept, this novel circuit eliminates the usage of an ordinary 180/spl deg/ hybrid at the power-amplifier output stage, therefore eliminating the losses associated with the hybrid, resulting in a compact and high-efficiency power-amplifier design with intrinsic second harmonic suppression. At an operating frequency of 4.15 GHz, a maximum measured power-added efficiency (PAE) of 60.9% at an output power of 28.2 dBm has been achieved. The measured PAE is above 50% over a 260-MHz bandwidth. Additionally, the second harmonic radiation is found to be 30 dB below the fundamental in both E- and H-planes. When the circuit is subjected to a two-tone test, the measured third-order intercept point is 37 dBm, about 10 dB above the P/sub 1 dB/ point.

Class G approach for low-voltage, high-efficiency PA design

Class G power amplifier (PA) design guidelines are presented and experimentally validated, showing the interesting features of the new approach. For the same operating conditions, the Class G amplifier exhibits superior performances if compared to a tuned load one in large signal gain, output power, and third-order intermodulation (IM3), with a power-added efficiency (PAE) improvement of 38.5%. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 366–378, 2000.

Push-pull power amplifier integrated with microstrip leaky-wave antenna

An X-band active integrated antenna push-pull power amplifier is presented that uses a dual feed microstrip leaky-wave antenna for both out-of-phase power combining and second harmonic tuning. This novel structure results in a compact and high efficiency power amplifier design. At the operating frequency of 8.7 GHz. A maximum measured PAE of 54% at an output power of 38.1 dBm has been achieved.

A large-signal model of self-aligned gate GaAs FET's for high-efficiency power-amplifier design

We propose a large-signal model that can simulate the power-added efficiency of p-pocket self-aligned gate GaAs MESFET's. This model includes a new drain current model and a gate bias-dependent RF output resistance to express the drain conductance and its frequency dispersion at each gate bias. In addition, gate-source and gate-drain capacitances are modeled by functions of two variables of gate and drain biases so as to fit the measured values of ion implanted channels. The simulated power-added efficiency agreed with the measured value with a maximum error of 5%. The intermodulation distortion was also simulated and the maximum difference between the simulated and measured results was reduced to one-fifth of the results simulated by the conventional model. Practical applications were demonstrated by the load-pull simulation and the /spl pi//4 shift QPSK-modulated signal simulation.

Design of high-efficiency RF Class-D power amplifier

In this paper, the losses in a Class-D RF switching power amplifier and their frequency dependence are described. The losses analyzed are the switching, conduction, and gate drive losses. A 300 W, 13.56 MHz, Class-D circuit is designed in the traditional manner to illustrate the magnitude of the different types of loss. A circuit using the ZVS equations developed in this paper is designed. An experimental circuit is built using standard IRF540 devices in TO220 packages. That circuit does not meet its performance goals because of the package inductance. A new low inductance half-bridge package is introduced to solve this problem. Techniques for circuit layout and power measurements for RF applications are also presented in the experimental section. A low loss gate drive circuit is also presented using a Class-E circuit to provide the drive power. The experimental results confirm the accuracy of the design equations derived in this paper.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Idealized operation of the class E tuned power amplifier

The class E tuned power amplifier consists of a load network and a single transistor that is operated as a switch at the carrier frequency of the output signal. The most simple type of load network consists of a capacitor shunting the transistor and a series-tuned output circuit, which may have a residual reactance. Circuit operation is determined by the transistor when it is on, and by the transient response of the load network when the transistor is off. The basic equations governing amplifier operation are derived using Fourier series techniques and a high- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> assumption. These equations are then used to determine component values for optimum operation at an efficiency of 100 percent. Other combinations of component values and duty cycles which result in 100-percent efficiency are also determined. The harmonic structure of the collector voltage waveform is analyzed and related amplifier configurations are discussed. While this analysis is directed toward the design of high-efficiency power amplifiers, it also provides insight into the operation of modern solid-state VHF-UHF tuned power amplifiers.