Intermodulation distortion in uhf transistors

Intermodulation distortion in transistors operating between 1 and 2 GHz has been studied. Four sources of nonlinearity in the transistor were examined and characterized by polynomials which were expressed in terms of the voltages at the transistor junctions. By incorporating these nonlinearities into a linear model, a nonlinear UHF transistor model was derived. The nodal equations of this nonlinear model were successively solved by expressing each nodal voltage in terms of a Volterra series expansion of the input voltage. Based on this analysis, predictions of the intermodulation distortions in two types of transistor were made; these predictions compared favourably with meansurements.     

A TCAD approach for non-linear evaluation of microwave power transistor and its experimental verification by LDMOS

A simulation technique is developed in TCAD to study the non-linear behavior of RF power transistor. The technique is based on semiconductor transport equations to swot up the overall non-linearity’s occurring in RF power transistor. Computational load-pull simulation technique (CLP) developed in our group, is further extended to study the non-linear effects inside the transistor structure by conventional two-tone RF signals, and initial simulations were done in time domain. The technique is helpful to detect, understand the phenomena and its mechanism which can be resolved and improve the transistor performance. By this technique, the third order intermodulation distortion (IMD₃) was observed at different power levels. The technique was successfully implemented on a laterally-diffused field effect transistor (LDMOS). The value of IMD₃ obtained is −22 dBc at 1-dB compression point (P _{1 dB}) while at 10 dB back off the value increases to −36 dBc. Simulation results were experimentally verified by fabricating a power amplifier with the similar LDMOS transistor.     

基于AD603程控增益大功率宽带直流放大器的设计

采用低噪声增益可程控集成运算放大器AD603和高频三极管2N2219和2N2905等器件设计了宽带直流放大器,该放大器具有增益可程控、功率高、频带宽、带宽可选择等特点。输入级采用两级AD603级联,以提高增益控制范围;中间级采用分立元件制作了高输出功率放大器,输出级设计了两路通频带分别为0～5MHz以及0～10MHz的低通滤波器实现带宽的可预置,通过51单片机可以对放大器增益和带宽进行控制。此外对提高直流放大器的各种性能指标提出了多种具体措施,在自动化要求较高的系统中具有很好的实用性。     

Application notes: 1-W high linear broadband RF power amplifier with Certesian feedback for TETRA modulation

Designing a high-linearity, high-efficiency RF power amplifier with wide bandwidth design is a real challenge. This article explores a technique to achieve 30 dBm output power with an adjacent channel power ratio (ACPR) of more than -65 dBc for frequency range of 800-900 MHz. A three-stage gallium arsenide heterojunction bipolar transistor (GaAs HBT) RF power amplifier with Cartesian feedback in closed-loop form is the main architecture of the design. An adaptive bias technique was used in the RF power amplifier design to achieve high linearity while preserving good efficiency.     

S parameters: a practical education

The course on radiofrequency amplifier design by the technique of S-parameters offered at Virginia Polytechnic Institute and State University is described with some emphasis on the associated laboratory portion of the course. The course begins with microstrip amplifier construction and the modeling of both lumped and distributed circuit elements. Attention is then given to the design of a transistor amplifier in the UHF spectrum. Biasing and parameter measurement are first considered. Matching networks are then designed and installed, followed by the measurement of several amplifier specifications. In five years of running the laboratory course there has never been a case of a student failing to end the course with a working amplifier. Typical amplifiers (900 MHz) have gains of 12 and 13 dB, input and output reflection coefficients below 0.05, third-order intercept points of 0-10 dBm (input), and noise figures near 5 dB     

A closed‐form equation approach to multi‐port/multi‐zone behavioral modeling of GaN FET Amplifiers

In this paper, a systematic method for the simulation of weakly and mildly nonlinear GaN FET amplifiers is reported. The core of the proposal is a third‐order Volterra‐based behavioral model with multi‐spectral and multi‐node capabilities that is formally derived from a circuit‐level representation. Starting with the equivalent circuit of a typical FET device with thermal power feedback and fading memory, described in terms of its large‐signal functions, closed‐form expressions for the kernels at the gate, drain and thermal nodes are developed up to the third order. The use of these kernels allows the calculation of the responses in the dc, first‐, second‐ and third‐harmonic zones, which are shown to be dependent on the frequency response of the amplifier circuit terminating impedances and thermal filter. The simulation approach has been applied to calculate the nonlinear response of a typical power amplifier circuit, showing the ability of the proposed approach to provide an accurate prediction of multi‐spectral, multi‐node, multi‐bias characteristics, including AM/AM‐AM/PM conversion, spectral regrowth, intermodulation, and temperature rise, under diverse input signal waveforms and bandwidths. These results have been successfully compared with commercial CAD tools based on harmonic balance or envelope simulation. Copyright © 2014 John Wiley & Sons, Ltd.     

基于小信号法的功率放大器的设计与仿真

射频功率放大器是数传发射机中的关键部件,它是制约整个系统性能的关键因素。依据固态功率放大器的小信号设计法,设计两级L波段固态功率放大器,给出了详细的设计流程和仿真数据。首先对放大器的增益,级间耦合,输入,输出匹配进行了初步仿真,然后通过提取管子的封装后的散射参数,对其进行最大输出功率匹配仿真,最后对放大器匹配和稳定性进行总体仿真,最终结果达到设计指标。     

基于IGBT的宽范围线性功率放大技术

模块化多电平分级逐段线性化思想可以大幅提高线性功率放大器的效率,绝缘栅双极型晶体管IGBT(insulated gate bipolar transistor)作为一种大功率器件用于其中将会大大简化大功率放大器的电路,但IGBT的类别中没有P沟道管,传统的复合P管用于线性功率放大时存在输出电压动态范围不足的问题。首先分析了该问题的形成原因,并提出一种宽动态范围的P-IGBT结构,然后分析了该结构的特性与功率放大机理,同理构造出特性完全对称的N-IGBT管,接着利用这2种异型对管构成互补线性功率放大器,最后通过实验验证了该技术的正确性。     

开关功率放大器非线性校正技术研究

开关功率放大器非线性主要来自器件本身,自适应预失真是用来补偿器件非线性失真的一种有效技术。针对开关功率放大器的非线性特性,文章首先建立它的模型,并使用NMSE评价指标对模型进行评价。在使输出线性化和功率最大化下,使用Wiener模型估计器来构成间接预失真线性化系统,并且用高斯-牛顿迭代法对预失真模型的参数识别进行优化。最后,仿真和实验结果都表明非线性校正的方法能有效补偿开关功率放大器的非线性失真,提高开关功放性能。     

基于有源PFC原理的升压型DC/DC空间电源设计

采用有源PFC工作原理实现了一种升压型DC/DC变换器模块。作为空间电源完成由蓄电池输出电压50￣90V范围到稳定的128V输出,所采用的核心控制芯片为L4981A。该变换器的设计采用了双闭环控制,其特点是采用电压误差放大器环节实现输出电压稳定,采用电流环误差放大器环节实现输入电流跟踪输入电压且连续。试验结果表明,该变换器的输入电流连续,输出电压精度高,负载调整率高,电压调整率高,纹波电压较低,EMI强度较低,输出功率达到1.5kW。     

基于FGMOS的电压求和电流传送器及其应用设计

本文提出了一种基于FGMOS晶体管的电压求和电流传送器的设计。通过对FGMOS晶体管的等效电路分析,得到其框图和等效电路,并设计出了其电路结构;为了表明提出的电压求和电流传送器的可用性,将提出的电压求和电流传送器用于实现受控振荡器和电压求和放大器;通过SPICE的仿真结果表明,基于FGMOS的电压求和电流传送器不仅具有高的线性特性,而且其电压传递增益和电流传递增益分别可达0.99和0.98。此外,还有着很好的频率响应性能,?0.5V的低电源电压,79.8?W的低功耗和在14k?~2.1M?的线性电子可调谐电阻值。基于电压求和电流传送器设计的受控振荡器具有稳定的正弦输出,而且振荡频率值可以通过偏置电流来控制,设计的电压求和放大器具有高输入电阻和可控的增益。     

DC-bus voltage control of three-phase AC/DC PWM converters usingfeedback linearization

In this paper, a fast voltage control strategy of three-phase AC/DC pulsewidth modulation (PWM) converters applying a feedback linearization technique is proposed. First, incorporating the power balance of the input and output sides in system modeling, a nonlinear model of the PWM converter is derived with state variables such as AC input currents and DC output voltage. Then, by input-output feedback linearization, the system is linearized and a state feedback control law is obtained by pole placement. With this control scheme, output voltage responses become faster than those in a conventional cascade control structure. For robust control to parameter variations, integrators are added to the exact feedback control law. Since the fast voltage control is feasible for load changes, it is shown that the DC electrolytic capacitor size can be reduced. In addition, the capacitor current is analyzed for size reduction of the capacitor. As is usual with PWM converters, the input current is regulated to be sinusoidal and the source power factor can be controlled at unity. The experimental results are provided to verify the validity of the proposed control algorithm for a 1.5 kVA insulated gate bipolar transistor PWM converter system     

A High-Efficiency Audio Power Amplifier Using a Self-Oscillating Switching Regulator

A new high-efficiency audio power amplifier has been developed. This amplifier consists of a conventional power amplifier and a self-oscillating switching power supply which is arranged to vary the power supply output voltage according to the input signal voltage. The new amplifier achieves a higher efficiency than the conventional amplifier, by making the collector voltage of the emitter-follower-transistor follow the waveform of the output signal. Applying this idea to class A amplifiers, a one-third power dissipation can be achieved compared with the conventional class A amplifier. A power MOSFET is used as a switcher. The switching frequency is from 150 kHz to 300 kHz. The new amplifier shows sufficient favorable characteristics. Switching noise is suppressed to a low noise level, which has no influence on the AM tuner or other audio equipment. By stabilizing the single-ended push-pull (SEPP) output transistors, the amplifier can reproduce high quality tone. The present idea is also applicable to dass B power amplifiers and may be suitable for PA or car audio power amplifiers.     

新型工频测试电源开关功放的设计

工频测试电源技术的关键取决于功率放大器的性能。针对传统的测试源仍然使用低效的线性功率放大器,本文设计了一种基于D类功放的新型工频测试电源开关功放。经过实物制作及测试,该功率放大器对输入的工频正弦信号进行电压放大,有效值范围为200×80%~200×115%,输出功率不小于20VA,THD不大于2%,能很好地满足实际应用的需求。由于该功率放大器采用BTL结构输出,输出功率仅取决于末级NMOS管,耐压可达直流500V,功率范围大,具有很大应用价值。     

宽带固态功率放大器的设计及实现

宽带固态功率功率放大器是固态发射机中的关键部件,广泛应用于软件无线电电台、有源相控阵雷达、综合化航空电子设备等领域中。以一款新研制的S波段宽带固态功率放大器为例,介绍了超宽带固态功率放大器的设计理论和方法,并用微波仿真软件ADS对功率管的输入、输出阻抗匹配电路及其偏置电路进行优化仿真设计。通过制作并测试此放大器,验证了该设计方法的可行性。最后,给出了测试数据它在2GHz～4 GHz的频带范围内,输入功率为25mW时,输出功率大于10W,带内功率起伏小于1.5dB。     

A new result in negative-feedback theory,and its application to audio power amplifiers

A nest of differentiating loops is described by means of which a very large amount of negative feedback can be applied to a specified stage in an amplifier (normally the output stage) with progresively less being applied to other stages. The effects of nonlinearity (other than hard limiting) in the specified stage can be virtually eliminated. The structure enables Bode's limit for loop-gain roll-off to be exceeded for the specified stage; both the frequency up to which loop gain is maintained constant and the frequency at which loop gain falls through unity are free design variables. As a result, practical difficulties associated with excess phase shift in low-frequency power transistors are minimized. The structure does not increase the susceptibility to transient overload and the resulting intermodulation. A practical amplifier using output transistors with fT～2 MHz has an output-stage loop gain of 25,000 (88 dB) at 20 kHz and 0.002 per cent harmonic distortion.     

A 0.7‐dB NF, +8.2‐dBm IIP3 CMOS low noise amplifier using frequency selective feedback

A CMOS amplifier employing the frequency selective feedback technique using a shunt feedback capacitor is designed and measured. The proposed amplifier can achieve a high IIP3 (input referred third‐order intercept point) by reducing the third‐ and second‐order nonlinearity contributions to the IMD3 (third‐order intermodulation distortion), which is accomplished using a capacitor as the frequency selective element. Also, the shunt feedback capacitor improves the noise performance of the amplifier. By applying the technique to a cascode LNA using 0.18‐µm CMOS technology, we obtain the NF of 0.7 dB, an IIP3 of +8.2 dBm, and a gain of 15.1 dB at 14.4 mW of power consumption at 900 MHz. Copyright © 2015 John Wiley & Sons, Ltd.     

A nonlinear macromodel for operational amplifiers

A general-purpose nonlinear macromodel of an operational amplifier is presented. All element values can be derived directly from typical specification sheets eliminating any testing to determine model parameters. The model simulates the following characteristics: voltage and current offsets, input impedance, nonlinear input bias currents, gain, multiple poles, nonlinear slew, common-mode gain, voltage and current limiting and output impedance.     

On the two‐port network analysis of common amplifier topologies

Using two‐port network transmission parameters, we derive exact expressions for the voltage/current gains and the input/output impedances of common amplifier topologies. The derived expressions are valid both for BJT and MOS‐based amplifiers and are independent of any particular small signal transistor model. Copyright © 2009 John Wiley & Sons, Ltd.