Measurement and control of current/voltage waveforms of microwavetransistors using a harmonic load-pull system for the optimum design ofhigh efficiency power amplifiers

One of the most important requirements that RF and microwave power amplifiers designed for radiocommunication systems must meet is an optimum power added efficiency (PAE) or an optimal combination of PAE and linearity. A harmonic active load-pull system which allows the control of the first three harmonic frequencies of the signal coming out of the transistor under test is a very useful tool to aid in designing optimized power amplifiers. In this paper, we present an active load-pull system coupled to a vectorial “nonlinear network” analyzer. For the first time, optimized current/voltage waveforms for maximum PAE of microwave field effect transistors (FET's) have been measured. They confirm the theory on high efficiency microwave power amplifiers. The proposed load-pull setup is based on the use of three separated active loops to synthesize load impedances at harmonics. The measurement of absolute complex power waves is performed with a broadband data acquisition unit. A specific phase calibration of the set-up allows the determination of the phase relationships between harmonic components. Therefore, voltage and current waveforms can be extracted. The measurement results of a 600 gate periphery GaAs FET (Thomson Foundry) exhibiting a PAE of 84% at 1.8 GHz are given. Such results were obtained by optimizing the load impedances at the first three harmonic components of the signal coming out of the transistor. Optimum conditions correspond to a class F operation mode of the FET (i.e., square wave output voltage and pulse shaped output current). A comparison between measured and simulated current/voltage waveforms is also presented     

太阳能最大功率点跟踪的航模电调设计

根据太阳能光伏输出特性,采用最小二分法实现最大功率点跟踪(MPPT),对于提高太阳能电池的输出功率及太阳能的利用率,特别是在控制电机等感性负载上,意义重大.在航模飞机上,太阳能飞机的飞行受太阳能板输出功率的直接影响,而航模飞机的电调采用中颖公司的SH79F168作为主芯片,太阳能最大功率输出也需要芯片控制太阳能板的输出电压,此设计的目的就是把两者合二为一,以节省空间并提高效能.     

Compact and low-power optical logic NOT gate based on photonic crystal waveguides without optical amplifiers and nonlinear materials

An optical logic NOT gate (OLNG) is presented based on photonic crystal (PhC) waveguides without nonlinear materials and optical amplifiers. Also, a way of determining the operating parameters is presented. It is demonstrated through finite-difference time-domain simulations that the structure presented can operate as an OLNG. The optimized contrast ratio, defined as the logic-"1" output power divided by the logic-"0" output power, is found to be 297.07 or 24.73 dB. The size of the OLNG can be as small as 7a×7a, where a is the lattice constant of the PhC. Further, the OLNG presented in this paper can operate at a bit rate as high as 2.155 Tbit/s, which is much higher than that of electronic or optical logic gates developed until now. Moreover, as it is not based on the nonlinear effect, the OLNG can operate at very low powers and a relatively large operating bandwidth. This is favorable for large-scale optical integration and for developing multiwavelength parallel-processing optical logic systems.     

Fiber-amplifier-enhanced photoacoustic spectroscopy with near-infrared tunable diode lasers

A new approach to wavelength-modulation photoacoustic spectroscopy is reported, which incorporates diode lasers in the near infrared and optical fiber amplifiers to enhance sensitivity. We demonstrate the technique with ammonia detection, yielding a sensitivity limit less than 6 parts in 10(9), by interrogating a transition near 1532 nm with 500 mW of output power from the fiber amplifier, an optical pathlength of 18.4 cm, and an integration time constant of 10 s. This sensitivity is 15 times better than in prior published results for detecting ammonia with near-infrared diode lasers. The normalized minimum detectable fractional optical density, alphaminl, is 1.8 x 10(-8); the minimum detectable absorption coefficient, alphamin, is 9.5 x 10(-10) cm(-1); and the minimum detectable absorption coefficient normalized by power and bandwidth is 1.5 x 10(-9) W cm(-1)/square root Hz. These measurements represent what we believe to be the first use of fiber amplifiers to enhance photoacoustic spectroscopy, and this technique is applicable to all other species that fall within the gain curves of optical fiber amplifiers.     

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.     

Power combining techniques into unbalanced loads for Class-E and inverse Class-E amplifiers

A power combining strategy for Class-E and inverse Class-E amplifiers operating at high frequencies such that they can operate into unbalanced loads is proposed. This power combining method is particularly important for the inverse Class-E amplifier configuration whose single-stage topology is naturally limited for small-to-medium power applications. Design examples for the power combining synthesis of classical Class-E and then inverse Class-E amplifiers with specification 3 V-1.5 W-2.5 GHz are given. For this specification, it is shown that a three-branch combiner has a natural 50 γ output impedance. The resulting circuits are simulated within Agilent Advanced Design Systems environment with good agreement to theoretical prediction. Further the performance of the proposed circuits when operated in a Linear amplification using Nonlinear Components transmitter configuration whereby two-branch amplifiers are driven with constant amplitude conjugate input phase signals is investigated.     

Siniglee-Staagee Amnplifierr-Aideed Current Transformers Possessing Small Ratio Errors at 60 Hz

Two directly coupled electronic techniques are described which reduce significantly the burden seen by a single-stage toroidal current transformer. Almost all the power is supplied by an electronic power amplifier so that magnetizing current within the transformer is extremely small Magnetic cores of small physical size may be used with small numbers of turns. Measured ratio errors at unity ratio are approximately 10 parts per million or less at 60 Hz provided certain restrictions are satisfied with respect to dc offset voltages within the electronic amplifier used. This particular technique lends itself to the use of modern packaged linear amplifiers which may be adapted for power use. Directly coupled electronic circuitry enables the techniques to be used at lower frequencies. Ratio error measurements are described and comparison made between the actual ratio errors obtained experimentally and the theoretically predicted values.     

Tunable high-power narrow-spectrum external-cavity diode laser at 675 nm as a pump source for UV generation

High-power narrow-spectrum diode laser systems based on tapered gain media in an external cavity are demonstrated at 675 nm. Two 2 mm long amplifiers are used, one with a 500 μm long ridge-waveguide section (device A), the other with a 750 μm long ridge-waveguide section (device B). Laser system A based on device A is tunable from 663 to 684 nm with output power higher than 0.55 W in the tuning range; as high as 1.25 W output power is obtained at 675.34 nm. The emission spectral bandwidth is less than 0.05 nm throughout the tuning range, and the beam quality factor M(2) is 2.07 at an output power of 1.0 W. Laser system B based on device B is tunable from 666 to 685 nm. As high as 1.05 W output power is obtained around 675.67 nm. The emission spectral bandwidth is less than 0.07 nm throughout the tuning range, and the beam quality factor M(2) is 1.13 at an output power of 0.93 W. Laser system B is used as a pump source for the generation of 337.6 nm UV light by single-pass frequency doubling in a bismuth triborate (BIBO) crystal. An output power of 109 μW UV light, corresponding to a conversion efficiency of 0.026% W(-1), is attained.     

一种测量微波功率放大器件输出端反射系数的新方法

本提出了一种测量微功率放大器件输出端反射系数的新方法。通过对可变负载在不同频率和位置下的校准,采用所建立的自动测量系统,运行专门编制的自动控制和数据处理软件,可对微波功率放大器件输出端反射系数进行测量,该方法具有测量简便、迅速、自动化程度高等优点。     

Extremely low thermal noise floor, high power oscillators usingsurface transverse wave devices

This paper presents state-of-the-art results on 1-GHz surface transverse wave (STW) oscillators running at extremely high loop power levels. The high-Q single-mode STW resonators used in these designs have an insertion loss of 3.6 dB, an unloaded Q of 8000, a residual PM noise of -142 dBc/Hz at a 1-Hz carrier offset, and operate at an incident power of up to +31 dBm in the loop. Other low-Q STW resonators and coupled resonator filters (CRF), with insertion losses in the 5-9 dB range, can conveniently handle power levels in excess of two Watts. These devices were incorporated into voltage controlled oscillators (VCO's) running from a 9.6-V dc source and provide an RF output power of +23 dBm at an RF/dc efficiency of 28%. Their tuning range was 750 kHz and the PM noise floor was -180 dBc/Hz. The oscillators, stabilized with the high-Q devices and using specially designed AB-class power amplifiers, delivered an output power of +29 dBm and exhibited a PM noise floor of -184 dBc/Hz and a 1-Hz phase noise level of -17 dBc/Hz. The 1-Hz phase noise level was improved to -33 dBc/Hz using a commercially available loop amplifier. In this case, the output power was +22 dBm. In all cases studied, the loop amplifier was found to be the factor limiting the close-to-carrier oscillator phase noise performance     

一种全桥式高功率放大器

用集成功率放大器驱动大功率三极管构成推挽功率放大器,两路推挽功率放大单元可以组合构成全桥式功率放大器,这种放大器大量使用大功率三极管等分立元件,能够提高电路总的额定功率,并且使元件布局分散有利于实现散热设计,工程样机研制证明该方法适用。水库测试结果表明:驱动某大型双谐振压电陶瓷换能器,功放样机输出连续信号时,在5 k Hz左右输出电功率达到1600 W以上。单频信号工作时观察信号波形,信号畸变与失真较小。根据试验与测试结果分析了末级三极管上的功率耗散情况,验证了工程样机在散热设计方面的有效性。     

Small signal analysis of quadrature LC oscillator operating at 59-62.5 GHz

In this study, a comprehensive small signal analysis method for quadrature oscillators based on crosscoupled LC-tuned oscillators and parallel coupling is proposed. The analysis is suitable for circuits operating up to millimetre wave frequencies since the key parasitics of all circuit elements such as core amplifiers, coupling amplifiers, buffers, inductors and varactors are considered. This allows for efficient circuit and device optimisations. The proposed method is based on the consequent parallelisation of all individual network elements into a simple overall equivalent RLC tank. The analysis is employed for CMOS but can also be adapted to other technologies. To verify the analysis, a circuit with oscillation frequency around 61 GHz was designed in 90 nm silicon on insulator (SOI) CMOS. Frequency control is enabled by adjusting the gain in the feedback amplifiers. Hence, no lossy varactors are necessary. At 50 Ωterminations, a supply voltage of 1.5 V and a total supply current of less than 56 mA, a tuning range above 3 GHz, an output power per channel of 219 dBm+1.5 dB and a phase noise of better than 280 dBc/Hz at 2 MHz offset are measured.     

蓝宝石输出窗的成功封接

基于多弧离子镀技术,结合特殊的封接结构和工艺技术,成功地实现了蓝宝石输出窗的真空气密封接.通过试验,证明封接的蓝宝石输出窗具有良好的真空气密性能、抗热烘烤冲击能力、较好的抗拉强度.这一成功为我国发展高功率和高频率真空微波、毫米波器件奠定了基础.     

Chaotic noise in superconducting microbridge 4-photon,X-band parametric amplifier

The anomalous noise rise observed in nearly all types of parametric amplifiers based on Josephson junctions has been an intriguing as well as annoying problem for many years. This phenomenon has been most spectactular in microbridge amplifiers. Here we present measurements on externally pumped single microbridge 4-photon unbiased amplifiers, where the slit with the bridge is used as a slotline resonantly coupled to the waveguide in an exceptionally simple coupling scheme. This scheme may be of interest in itself, particularly if the noise problem can be overcome, and in other connections. Up to 16 dB gain was obtained at the top of the waveguide. However, the noise rise was observed as usual. An analog computer study on a model including an input/output circuit was performed. The results are in very good agreement with the experiments. The amplification is heralded by a seemingly chaotic noise rise. this noise is then amplified linearly when gain occurs. Amplification is found to take place very close to where the supercurrent is completely suppressed by the pump. The cause of the noise rise has previously been interpreted as loss of phaselock. However, the power spectra of the time-derivative of the phase show this still to be locked in the region of positive gain. Furthermore, computations of the Lyapunov exponents show one to be positive in the region where gain occurs, reaching a maximum value at the parameters corresponding to maximum gain. We therefore conclude that chaotic noise is indeed present in Josephson junction parametric amplifiers where low-impedance devices such as microbridges with negligible capacitance are used as the active elements.     

静态电荷量测试仪校准源研制

静态电荷量标准采用精密程控电压源和精密电容器输出高准确度静态电荷量,利用电压负反馈进行自动调整,克服负载电容和输出电压对输出电荷量的影响,实现静态电荷量的稳恒输出,可方便地检定静电计和电荷放大器。该静态标准电荷源的稳恒特性比传统的电荷源提高了5个数量级。该标准源静态电荷量Qx范围为200pC～2μC;允许误差为0.1%Qx+0.1pC;等效源内电容为10^-15F。     

Measurement of Operational Amplifier Characteristics in the Frequency Domain

A test circuit for the automatic measurement of integrated-circuit operational amplifiers in the frequency domain has been developed. The main advantage of this test circuit over those previously reported in the literature is that it uses buffers in the feedback loop to reduce the influence of the output impedance of the operational amplifier. A fit program has been developed to extract the relevant parameters such as the transfer characteristics, the common mode rejection ratio, and the power supply rejection ratio. Examples of measurements are added for several operational amplifiers.     

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.     

Design of a 10 PW (150 J/15 fs) peak power laser system with Ti:sapphire medium through spectral control

We designed a 10 PW (150 J-15 fs) laser system based on the use of titanium-doped sapphire power amplifiers. The solution is to provide an overall compensating spectral gain narrowing and shifting technique for obtaining a controlled output spectrum.     

Ultrasonic treatment restores the photoelectric parameters of silicon solar cells degraded under the action of <Superscript>60</Superscript>Co gamma radiation

The photoelectric parameters of silicon solar cells degraded under the action of ⁶⁰Co gamma-radiation can be partly restored using an ultrasonic treatment (UST). The growth of the maximum output power of solar cells after the UST is related to a redistribution of the radiation defects and an increase in the homogeneity of a semiconductor crystal structure.     

Active phase locking of fiber amplifiers using sine-cosine single-frequency dithering technique

The sine-cosine single-frequency dithering technique for active phase locking of fiber amplifiers is presented for the first time to our knowledge. It has twice the phase control speed as the single-frequency dithering technique. Detailed theoretical development has been presented and the relevant experiment has been done. In the experiment, nine 10 W level fiber amplifiers are tiled into 3×3 array and the total output power is about 100 W. The sine-cosine single-frequency dithering algorithm is run on a signal processor based on a field-programmable gate array for phase control on the fiber amplifiers. When the phase control system is in a closed loop, the fringe contrast of far-field intensity pattern is improved by more than 90% from 21% in an open loop, and the residual phase error is less than λ/20.