On the linearity and efficiency of outphasing microwave amplifiers

A new approach for the analysis of the efficiency and linearity of Chireix-outphasing combiners is presented. The approach takes into account, in an explicit manner, the effect of impedance mismatch between the amplifiers and the lossless combining structure. It is shown that the impedance mismatch leads to new expressions for the output voltages from both branches of the amplifier. These expressions explain the origin of the lack of linearity reported in the literature for the Chireix architecture and lead to a new expression for the instantaneous efficiency of a Chireix combiner. Various simulations using a commercial simulator are performed and their results are compared to those predicted by the derived equations. A quasi-exact agreement between the simulator and derived equations is found for all simulations conducted, including voltage expressions, linearity analysis, and instantaneous and average efficiency calculations for a code-division multiple-access signal. The impact of combiner parameters on its linearity and efficiency is also studied.     

Semiconductor diode amplifiers and pulse modulators

The reverse recovery characteristic of a semiconductor diode depends not only on the crystal properties and the physical dimensions of the diode but also on the circuit in which it is used. The effects of the circuit parameters, namely, forward current, reverse voltage and reverse loop impedance, on the diode recovery characteristics were studied experimentally on germanium and silicon junction diodes. The results are given in curves which illustrate the relationships between these circuit parameters and the maximum reverse current, as well as the constant current duration. Based on these curves, circuit applications were developed. The experiments on a pulse amplifier performed by the National Bureau of Standards, were repeated. The results showed a maximum power gain of 22 db per stage. Four pulse modulator circuits were designed. They are amplitude modulator, sampler, pulse duration and position modulators. Linearity and frequency response tests on these modulator circuits were conducted. The results indicated that they have small distortion and flat frequency response from dc up to several tens of kilocycles per second. Modifications of the pulse amplitude modulator provides amplifiers for continuously varying signals. Four such circuits are given.     

A high power active circulator using GaN MMIC power amplifiers

This paper presents a 2.4 GHz hybrid integrated active circulator consisting of three power amplifiers and three PCB-based Wilkinson power dividers.The power amplifiers were designed and fabricated in a standard0.35- m Al Ga N/Ga N HEMT technology,and combined with three traditional power dividers on FR4 using bonding wires.Due to the isolation of power dividers,the isolation between three ports is achieved; meanwhile,due to the unidirectional characteristics of the power amplifiers,the nonreciprocal transfer characteristic of the circulator is realized.The measured insertion gain of the proposed active circulator is about 2–2.7 d B at the center frequency of 2.4 GHz,the isolation between three ports is better than 20 d B over 1.2–3.4 GHz,and the output power of the designed active circulator achieves up to 20.1–21.2 d Bm at the center frequency.     

Low cost measurement system for broadcast power amplifiers

For the fast prototyping, production, and delivery of commercial radio frequency products/systems, accurate and reliable test systems are necessary. These systems are usually product customized and thus expensive solutions, capable of performing all necessary measurements for a specific product. The purpose of this paper is to present a flexible cost‐effective test solution, capable of realizing all necessary measurement on a high output power amplifier system greater than 500 W, and to generate essential reports. These reports allow the system operator to (i) perform an analysis and a statistical comparison among various products, assuring that the quality is the same for all products; and (ii) retain products that present a performance poorer than other similar products, without a rigorous technical analysis, thus increasing efficiency in factory assembly line. Copyright © 2013 John Wiley & Sons, Ltd.     

高效率Doherty放大器的设计与仿真

效率和线性度是功率放大器的两个重要指标,影响着整个系统的性能.通过比较各种提高效率的方法中,选择结构简单的基于Doherty技术的功率放大器来实现.首先介绍了Doherty功率放大器的基本工作原理,然后选用飞思卡尔的MRF6S21140H芯片,应用微波仿真软件ADS设计了频段在2110～2170MHz的高效率Doher...     

Linearisation of microwave power amplifiers using active feedback networks

A new technique for linearising microwave power amplifiers is presented. Analytical and experimental results show that the intermodulation distortion in power amplifiers can be seriously reduced when active feedback networks are employed.     

Chip for linearisation of RF power amplifiers using digitalpredistortion

A digital VLSI chip is presented that implements the most critical part of a predistortion system for linearisation of RF power amplifiers. Measurements have shown that the chip provides seven times higher modulation bandwidth (208 kHz) at 10% power (100 mW) compared with a standard digital signal processor     

PWM功率放大器在直流伺服系统中的应用

介绍了PWM功率放大器的基本概念和分类,详细说明了H型双极可逆PWM系统的工作原理及其与单极、受限单极的区别。研制了基于智能功率模块PM75CES060的H型可逆PWM功率放大器,实验结果表明该系统具有高可靠性和较好的实用价值。     

Integrated overcurrent protection system for class-D audio power amplifiers

A fully integrated overcurrent protection system is presented suitable for application in integrated class-D audio power amplifiers. Accurate overcurrent detection is used based on parallel measurement of the voltage drop across the DMOS power transistors. A logic circuit enables continuous current limiting during overload situations. Actual short circuits can be distinguished from load impedance minima using a simple short-circuit discrimination method.     

A millimeter-wave six-port reflectometer using dielectric waveguide

A six-port reflectometer circuit that is particularly suited to dielectric-type waveguides is described. Its scattering matrix is derived, allowing for flexibility in design. A phase-shifting network is incorporated in the circuit, and it is shown that a quadrature hybrid can be configured for this purpose. The reflectometer was implemented in a dielectric waveguide for W-band (75 GHz-110 GHz) operation, and measurements are presented     

Optimization of EDGE terminal power amplifiers using memoryless digital predistortion

This paper describes a lookup-table (LUT)-based digital predistortion system usable for enhanced data for global system for mobile evolution (EDGE) handset transmitters. The system is memoryless and capable of improving average efficiency and performance in terms of the leakage power at offset frequencies and error vector magnitude. The obtainable efficiency at maximum linear output power is comparable, but at backoffs superior to commercial EDGE power amplifiers (PAs). Minimum system requirements on word length and LUT size have been investigated, which shows that a LUT having approximately 500 coefficients and a system word length of 13 bits are sufficient for EDGE. The proposed system is simple compared to basestation implementations comprising PA memory compensation and can be easily implemented in handsets in order to improve the overall system performance. The effects of antenna mismatch on system performance have been investigated     

Efficiency enhancement for power amplifiers using dynamic bias switching technique

A dynamic bias switching technique is presented which discretely switches supply voltages according to the signal envelope level. For the detected envelope signals which ate lower than an appropriate threshold, this technique dynamically switches the transistor's drain bias to a significantly lower voltage. For verification, a dynamic bias switching system, applied to a class-AB power amplifier for the 859 MHz band, was implemented. Using a down-link wideband code division multiple access (WCDMA) signal, improved output power of 0.5 dB from 30.5 to 31 dBm, and improved PAE of 8.1% points from 27.4 to 35.5% wete achieved at a given ACLR level of -30 dBc compared to the conventional single-supplied class-AB amplifier.     

Integrated-antenna push-pull power amplifiers

In this paper, the integrated-antenna concept is applied to push-pull power amplifiers (PAs). In this approach, the antenna serves as an out-of-phase power combiner and tuned load for higher harmonics. This new architecture effectively has a near-zero loss output hybrid, and results in a high-efficiency PA. The first example is a narrow-band push-pull amplifier integrated with a dual-feed patch antenna. At an operating frequency of 2.5 GHz, a maximum measured power-added efficiency (PAE) of 55% is achieved. The second example is a broadband push-pull amplifier integrated with a dual-feed slot antenna amplifier operating at 2.46 GHz which has a peak PAE of 63%, and PAE better than 55% in an 8% bandwidth. Additionally, 48% PAE is achieved with code-division multiple-access modulation and adjacent-channel power ratio better than -42 dBe at a 1.25-MHz offset     

Calibration and measurement of a wideband six-port polarimetricmeasurement system

The principle of operation, calibration procedure, and experimental results of a wideband six-port polarimetric measurement system are described in this paper. This measurement system can measure the polarization states of incoming waves and the polarimetric scattering matrices of scattering targets from the wideband power data. The imbalances and coupling between antenna polarization channels and the characteristics of microwave components used in the measurement system are calibrated using three partly unknown scattering calibrators that are illuminated by four unknown-polarized calibrating waves     

Instrumentation amplifiers using operational transconductance amplifiers

Instrumentation amplifier circuits using operational transconductance amplifiers (OTAs) as active circuit elements are proposed in this paper. Two new instrumentation amplifier circuits have been described and experimentally verified, where the first circuit comprises four OTAs and five resistors and the second circuit comprises two OTAs and three resistors.     

三波长反向泵浦喇曼放大器的优化与系统实现

将三波长反向泵浦的光纤喇曼放大器的增益优化问题转化为有约束条件的非线性规划问题,并用二次规划法求解。在优化结果的指导下,建立了实验系统,并利用放大的自发喇曼辐射谱微调泵浦功率实现了70nm带宽上平均增益为10dB、增益波动小于1dB的喇曼放大。     

Multi-order predistortion of power amplifiers using a second harmonic based technique

A novel multi-order predistortion linearizer is proposed to achieve independent control of the third- and fifth-order intermodulation products in high power amplifier. The approach is based on a combination of the second harmonic technique and the difference frequency technique. The second harmonic and difference frequency terms are generated using an envelope detector and two frequency multipliers. The RF predistorter has the advantage of low insertion loss and the requirement of a short delay line. Experimental results demonstrate an adjacent channel power ratio (ACPR) reduction of 11 dB for W-CDMA, at 2140 MHz.     

Wide-band dynamic modeling of power amplifiers using radial-basis function neural networks

A radial-basis function neural network (RBFNN) has been used for modeling the dynamic nonlinear behavior of an RF power amplifier for third generation. In the model, the signal's envelope is used. The model requires less training than a model using IQ data. Sampled input and output signals were used for identification and validation. Noise-like signals with bandwidths of 4 and 20 MHz were used. The RBFNN is compared to a parallel Hammerstein (PH) model. The two model types have similar performance when no memory is used. For the 4-MHz signal, the RBFNN has better in-band performance, whereas the PH is better out-of-band, when memory is used. For the 20-MHz signal, the models have similar performance in- and out-of-band. Used as a digital-predistortion algorithm, the best RBFNN with memory suppressed the lower (upper) adjacent channel power 7 dB (4 dB) compared to a memoryless nonlinear predistorter and 11 dB (13 dB) compared to the case of no predistortion for the same output power for a 4-MHz-wide signal.