A six-port network analyzer load-pull system for active load tuning

An experimental six-port network analyzer has been used as a load-pull system in an active load tuning configuration. It is shown that by using a dual six-port reflectometer and an appropriate calibration procedure, it is possible to measure at the same reference plane the ratio between the incident and reflected waves and the power flow at the output of the test transistor. Using these two values the simulated load impedance seen by a transistor and the microwave power delivered to the simulated load are calculated. Experimental results on microwave transistor characterization confirm the validity of this method. This technique uses less hardware than conventional methods, and presents a comparable accuracy to conventional techniques     

Experimental comparison of load-pull measurement systems fornonlinear power transistor characterization

Load-pull measurements are essential to accurately characterize power devices. This paper presents a comparison of measurement systems based on a load-pull configuration. The experimental results performed on a power MESFET transistor (1 W) are compared in terms of output power level and power added efficiency under variable operating conditions, i.e., load impedances and input power levels     

平衡式E/F类功率放大器的设计与实现

为了解决功率放大器设计过程中存在的效率低和输入/输出端回波损耗较大的问题,设计了一种工作频率为1.5 GHz的平衡式功率放大器。通过采用3 dB定向耦合器对射频信号进行分配及合成,大大降低了输入/输出端的驻波系数,并将逆F类功率放大器的谐波控制网络引入E类功率放大器的匹配电路中。使用ADS对晶体管进行负载牵引和源牵引,得到晶体管的输入/输出阻抗,同时结合晶体管的寄生参数,在输出匹配电路中对二次谐波、三次谐波分别进行开路和短路处理,且为了进一步提高功率放大器的工作性能,在输入电路结构中抑制了二次谐波。选用GaN HEMT器件CGH40010F晶体管,利用ADS软件进行电路仿真,并采用Rogers4350b高频板材制作该功率放大器的实际测试电路板。仿真优化和实测表明：在输入功率为28 dBm时,该功率放大器的输出功率为41.54 dBm,漏极效率为76.99%,功率附加效率（power additional efficiency,PAE）达到73.59%,输入/输出端驻波系数小于2,同时具有160 MHz的高效率带宽,且最大输出功率较单管功率放大器提高了3 dB。实测结果与仿真数据有一定的误差,但仍有较好的一致性,满足设计指标要求,验证了设计方法的可行性。该设计方法具有效率高和回波损耗低的优势,提高了功率放大器的设计效率,使它在当今高效绿色节能的射频微波通信系统中具有广阔的应用前景。     

负载牵引系统校准结果性能评价方法研究

针对采用标准失配衰减网络实现负载牵引测量系统校准时,转换增益测量误差△GT作为校准结果无法直观反映系统测量输出功率(Pout)以及功率附加效率(PAE)的测量性能问题.通过在后端模块的负载端插入经校准的精密极化步进衰减器对△GT进行衰减替代测量,给出了校准结果△GT与Pout及PAE变化量的曲线族,方便设计师快速获取系...     

Multiharmonic generators for relative phase calibration ofnonlinear network analyzers

Multiharmonic generators are of interest for determining coupler phase dispersion of nonlinear network analyzers inherently dealing with nonsinusoidal waveforms for RF current-voltage (I-V) measurements. Supported by simple waveform analysis, two on-wafer devices are experimentally evaluated: a single diode and a nonlinear transmission line (NLTL). The investigation uses an active harmonic load-pull system with 2 GHz fundamental frequency. It turns out that the NLTL is well suited as a reference generator. We present measurement examples of phase dispersion for different directional couplers up to 18 GHz and the application to RF I-V waveforms of a 1-W power HBT with harmonic load tuning     

微波功率固态放大器负载牵引特性的自动测试

提出了一种新的微波功率固态放大器件负载牵引测试方法和校准方法，研制了自动测试系统，并对该测试方法、校准方法和自动测试系统进行了较为详细的讨论。通过实测，获得了微波功率固态放大器输出功率等值线阻抗圆图，验证了所提出的校准方法、测试方法和自动测试系统测试方案是正确的，并具有实用性。     

Exploring figures of merit associated with the suboptimum operation of class-E power amplifiers

Closed-form design equations for the operation of a class-E amplifier for zero switch voltage slope and arbitrary duty cycle are derived. This approach allows an additional degree of freedom in the design of class-E amplifiers which are normally designed for 50% duty ratio. The analysis developed permits the selection of non-unique solutions where amplifier efficiency is theoretically 100% but power output capability is less than that the 50% duty ratio case would permit. To facilitate comparison between 50% (optimal) and non-50% (suboptimal) duty ratio cases, each important amplifier parameter is normalised to its corresponding optimum operation value. It is shown that by choosing a non-50% suboptimal solution, the operating frequency of a class-E amplifier can be extended. In addition, it is shown that by operating the amplifier in the suboptimal regime, other amplifier parameters, for example, transistor output capacitance or peak switch voltage, can be included along with the standard specification criteria of output power, DC supply voltage and operating frequency as additional input design specifications. Suboptimum class-E operation may have potential advantages for monolithic microwave integrated circuit realisation as lower inductance values (lower series resistance, higher self-resonance frequency, less area) may be required when compared with the results obtained for optimal class-E amplifier synthesis. The theoretical analysis conducted here was verified by harmonic balance simulation, with excellent agreement between both methods.     

Analysis and evaluation of harmonic suppression of lumped-element networks suitable for high-frequency class-E operation condition approximation

The harmonic output of microwave lumped-element class-E load-coupling topologies is assessed. Measurement results on fabricated C-band class-E power amplifiers with either a modified lowpass and an optimised second-harmonic impedance network show that the latter provides better performance not only in terms of output power, gain and efficiency, but also in regard to harmonic suppression. Compared with the common modified lowpass network, harmonic content in the load of the optimised second-harmonic impedance topology at the second-, third- and fourth-harmonic frequencies are lower by more than 5.8, 10 and 5.8 dB, respectively.     

A Comprehensive Mixed-Mode Time-Domain Load- and Source-Pull Measurement System

We present a novel test set devised for nonlinear balanced device characterization using load-pull techniques. The system is capable of measuring the voltage and current waveforms at the calibration reference planes while independently tuning the device under test (DUT) source and load differential- and common-mode terminations. The test set is designed to address present and future large-signal multiport measurement needs, easing the characterization task while developing new multiport active devices.      

Highly efficient <Emphasis Type="Italic">X</Emphasis>-range AlGaN/GaN power amplifier

The development of microwave power amplifiers (PAs) based on transistors with an AlGaN/GaN heterojunction are discussed in terms of the possible enhancement of their efficiency. The main focus is on the synthesis of the transforming circuits, which ensure the reactive load at the second- and third-harmonic frequencies and complex impedance at the fundamental frequency. This makes it possible to optimize the complex operation mode of a PA; i.e., to reduce the scattering power and enhance the efficiency. A microwave PA based on the Schottky-barrier-gate field-effect transistor with 80 electrodes based on the GaN pHEMT transistor with a gate length of 0.25 nm and a gate width of 125 nm is experimentally investigated. The amplifier has a pulse output power of 35 W and a power-added efficiency of at least 50% at a working frequency of 9 GHz.     

大反射负载牵引测量系统校准参数优化选取及应用

相对于传统负载牵引测量系统,大反射负载牵引测量系统可以对微波功率放大器件的负载阻抗端实现更大的调配范围,成为目前比较流行的测量方案。对大反射负载牵引测量系统的验证,一般选择转换功率增益作为负载牵引测量系统优化验证参数。通过对比功率增益和转换功率增益的理论值和测量值的偏差,认为在大反射条件下,功率增益对系统校准后的剩余误差更加敏感,对系统准确度优化提升效果更好。最后通过功率优化的应用实验验证,在负载反射系数为0.9时,转换功率增益变化0.4dB,而功率增益变化0.8dB,因此,选取功率增益作为大反射优化校准参数效果更明显,而在小反射系数下可选择转换功率增益作为负载牵引测量系统验证参数。     

Schematics of magnetically-elastic pressure transducers

Conclusions Experiments have shown that all three types of transducers with an appropriate selection of parameters have virtually linear output characteristics. Transducers with a variable inductance have a larger output power compared with the type of transducers made by the Swedish firm ASEA. The load resistances carry the difference of two voltages, the original biasing voltage and the voltage drop across a ballast lamp or the collector circuit of a transistor.The output power of a transistor with a variable inductance operating in a condition of free magnetization can be raised by measuring the magnetizing current increment and then amplifying it by means of the variable resistance which shunts the load and consists of a transistor or a magnetic amplifier with a negative current feedback through the transducer circuit.A suitable transducer circuit can be selected on the basis of specific conditions and requirements and by means of the comparison tests described in this work.N. P. Kunitskii and S. V. Krayushkin participated in the investigation of transducers with a variable inductance operating in a free or forced magnetization condition.     

On-line measurement of equivalent parameters for harmonicfrequencies of a power distribution system and load

A method is discussed for on-line measurements of parameters of a power distribution system and its associated load. Four parameters are measured: the complex impedances of the distribution system and the load for harmonic frequencies; the complex rms (crms) values J_n of the harmonics of the load current j and the crms values E_n of the harmonics of the distribution system voltage e. The measurements are performed on two states of the system before and after it is disturbed by either connecting to it a capacitor or a harmonic generating device. The results of physical measurements are compared with those calculated from a model     

Measurement of apparent power components in the frequency domain

An algorithm and a digital signal-processing technique are proposed for the measurement of the apparent power components in the frequency-domain approach. The discrete Fourier transform (DFT) is applied to simultaneous samples of voltage and current waveforms to compare their respective spectra. The RMS values of the harmonic currents flowing between the source and the load (resistive, reactive, and generated by the load nonlinearity) are calculated. The algorithm evaluates V_RMS, I_RMS and the active power in both the time and frequency domains, and the resistive, reactive, and complementary power components in the frequency domain     

High-frequency time-ratio control with insulated and isolated inputs

Fast-responding amplifiers are needed in many industrial and defense systems. Systems using power amplifiers with one to 1000 watts of output dc power require high performance. The requirements often include high efficiency, light weight, compactness, high reliability, economy, and simplicity, along with fast response and insulated multiple inputs. These performances are required in applications such as controls for high-power inverters and converters, motors, generators, light, heat, dc-to-ac inverters, power supplies, servo systems, etc. This paper presents a transistor-magnetic power amplifier with multiple insulated and isolated inputs (Fig. 1) with characteristics in Fig. 2. The technique of time-ratio control [1] is used to provide light weight, compactness, high efficiency, and high reliability. High-speed power transistors (0.1 μs) combined with a tunnel diode circuit permit high chopping frequency (50 kc). The base current of the power transistor is switched in-less than 0.02 μs. Insulated and isolated inputs are provided by a small saturable transformer the size of a TO-5 transistor case. Transistor inputs are used on the saturable transformer. Germanium power transistors (such as 2N1907) are used to provide economy, but silicon transistors can be used for applications at high ambient temperature. The circuit of Fig. 1 is used to fire controlled rectifiers for inverters and converters. A pulse transformer in series with a resistor replaces the load of Fig. 1 when needed in firing circuits. A simple time-ratio control (TRC) circuit is presented that controls the output [Fig. 2(a)] by varying the chopping frequency from 50 kc to 5 kc. The multiple inputs are illustrated. A constant frequency (50 kc) TRC is presented that controls load voltage from zero to the supply voltage [Fig. 2(b)]. The output responds to the control signal in 40 μs. The tunnel diode switching circuit is also presented.     

SOI single-electron transistor with low RC delay for logic cells and SET/FET hybrid ICs

We report on a successful fabrication of silicon-based single-electron transistors (SETs) with low RC time constant and their applications to complementary logic cells and SET/field-effect transistor (FET) hybrid integrated circuit. The SETs were fabricated on a silicon-on-insulator (SOI) structure by a pattern-dependent oxidation (PADOX) technique, combined with e-beam lithography. Drain conductances measured at 4.2 K approach large values of the order of microsiemens, exhibiting Coulomb oscillations with peak-to-valley current ratios /spl Gt/1000. Data analysis with a probable mechanism of PADOX yields their intrinsic speeds of /spl sim/ 2 THz, which is within an order of magnitude of the theoretical quantum limit. Incorporating these SETs as basic elements, in-plane side gate-controlled complementary logic cells and SET/FET hybrid integrated circuits were fabricated on an SOI chip. Such an in-plane structure is very efficient in the Si fabrication process, and the side gates adjacent to the electron island could easily control the phase of Coulomb oscillations. The input-output voltage transfer, characteristic of the logic cell, shows an inverting behavior where the output voltage gain is estimated to be about 1.2 at 4.2 K. The SET/FET hybrid integrated circuit consisting of one SET and three FETs yields a high-voltage gain and power amplification with a wide-range output window for driving the next circuit. The small SET input gate voltage of 30 mV is finally converted to 400 mV, corresponding to an amplification ratio of 13.     

Microwave power amplifiers based on AlGaN/GaN transistors with a two-dimensional electron gas

A technique for synthesis of microwave power amplifiers based on transistors with a AlGaN/GaN heterojunction is discussed. Special focus is on the development of a technique for synthesis of transformation circuits of the power amplifier to increase efficiency with a retained high output power. The use of independent matching at the harmonic frequencies and fundamental frequency makes it possible to control the attainable efficiency in a wide frequency band along with the total suppression of harmonics beyond the operational band. Microwave power amplifiers for operation at 4 and 9 GHz have been developed and experimentally investigated.     

一种高稳定度纯净正弦波功率信号源的研制

针对传统信号源输出电压较低,负载能力弱且无法闭环稳压、稳频的缺点,研制了一种输出电压有效值为40V,负载电流为1A的高稳定度纯净正弦波功率信号源,以适应陀螺测试等系统的需求．本文对该功率信号源系统结构和电路原理进行了详细的分析．样机实验结果表明：该信号源具有功率大、稳定度高,准确度高和低谐波含量的优点,具有良好的应用前景．     

Active feedback circuit for minimization of voltage transientsduring pulsed measurements of semiconductor devices

The operation of an active feedback circuit that minimizes voltage transients during pulsed-I-V measurements is presented. A field-effect transistor (FET) is used as the nominal device under test (DUT). The feedback circuit detects the sag in drain voltage that is caused by voltage drops produced across both the inductor in the drain bias tee and any series resistance in the drain-current path. The feedback signal consists of the current injected into the drain circuit that is sufficient to minimize the change in drain voltage. The feedback circuit actively synthesizes a small driving-point impedance that is seen by the drain of the DUT and is on the order of 10^-2 Ω. Larger voltages do not need to be applied to the drain circuit in order to overcome the nominal inductive and resistive voltage drops. Therefore, a low-current power supply can be used to set V_ds for low- or high-power FETs. Transient responses with and without the use of the feedback circuit are presented. Pulsed-I-V measurements using this feedback method (made less than 1 μs after the start of the gate pulse) of a high-power FET are also presented     

Analysis and design of high-efficiency variable conduction angle doherty amplifier

The Doherty amplifier was first proposed to improve the efficiency under output power back-off using the technique of load-line modulation of a `carrier? amplifier through a `peak? amplifier. By varying input bias of the peak amplifier along with load of the carrier amplifier at low drive levels, different topologies of the Doherty amplifier are distinguished. An analytical analysis that determines the optimum output performance of these topologies in terms of output power, efficiency and output power back-off ensuring a near-peak efficiency is developed. The presented comprehensive analysis considered for variation of conduction angle of the peak amplifier biased class C. New design equations of the analysed topologies are derived. A realisation at a central frequency of 1.9 GHz using GaAs field effect transistor (FET) devices of a Doherty amplifier topology is reported. In this topology the carrier operates (at low drive levels) into load impedance 5/2 times larger than its optimum. Power-added efficiency of 61.8% is measured at P/sub 1dB/ of 25.9 dB m and 33.2% is measured at 9 dB back-off from P/sub 1dB/.