Hybrid predistortion to compensate third- and fifth-order intermodulation of a 2 GHz power amplifier using cuber predistortion and second harmonics injection

A new circuit construction technique that actively utilises second harmonics injection (HI) to realise fifth-order predistortion (PD) for power amplifiers (PAs) with memoryless AM/AM and AM/PM conversions is proposed. Applying a combination of the proposed technique and cuber predistortion (CPD) to third-order distortion yields the simultaneous compensation of both third- and fifth-order intermodulation distortion (IM3 and IM5); capabilities are not possible with the conventional third-order PD approach. Since the proposed method can be implemented as a simple analogue circuit, it betters compactness and lowers cost. In order to derive the PA bias condition at which second HI works most effectively, a complex power series nonlinear model that allows both amplitude and phase nonlinearities to be dealt with simultaneously is used. To confirm the author's compensation theory, a 2 GHz band PA and a hybrid lineariser that employs second HI and CPD are fabricated and experiments are performed. About a 20 dB simultaneous reduction in IM3 and IM5 is achieved with the two-tone test. A W-CDMA one-carrier test is also conducted to verify the improvement in adjacent channel leakage power ratio compared with CPD only.     

A novel nonlinear distortion characterisation standard for RF andmicrowave communication systems

Theoretical results obtained with a simplified third order memoryless nonlinear system have shown that multitone test characteristics can be directly related to the more usual two-tone test figures. These theoretical developments have also proved that the noise power ratio (NPR) gives an optimistic measure of co-channel distortion. A corrected co-channel power ratio (CCPR) characterisation standard and its associated laboratory measurement set-up have therefore been proposed to circumvent the failings of the NPR. The usefulness of this approach is illustrated by some measurements of a practical C-band amplifier circuit     

Minimisation and accurate modelling of memory effects in frequency multipliers

Sources of memory effects in frequency multipliers are investigated and their minimisation methods as well as the improved behavioural model are suggested. The memory effects are well known to exist in power amplifiers since they handle high-power signals and have bias networks, and recent research has shown that some amount of memory effects also exist in frequency multipliers. As such, impedance analysis at the harmonic and the envelope frequencies for a frequency tripler was performed, and the results show that the memory effects in the device are dominated by the harmonic resonant networks at the input and output. Hence, the minimisation technique of memory effects in the harmonic networks of the tripler was suggested and the following two-tone measurement showed intermodulation distortion asymmetry improvements with the optimisation technique on a frequency tripler at 2.55 GHz. In addition, a phase-folded parallel-cascade method was employed to successfully model the memory effects of frequency multipliers. The accuracy with the method was improved by 3 dB on a Schottky-diode frequency tripler, and the identified location of memory effects was concentrated in 2.8?6.2 kHz and above 78 kHz, which is consistent with the results of the two-tone test.     

Determination of Nd isotopes in water: a chemical separation technique for extracting Nd from seawater using a chelating resin

A new preconcentration technique for the determination of the concentration and isotopic composition of neodymium in aqueous samples is presented. The method uses a resin, Nobias PA1 from Hitachi High-Technologies, which has a hydrophilic methacrylate polymer backbone where the functional groups ethylenediaminetriacetic and iminodiacetic acids are immobilized. The function of the resin has been tested by preconcentrating 110-350 pmol of Nd from test solutions as well as from natural brackish water and seawater samples with different salinities and Nd concentrations. Samples were loaded onto the resin after the pH was adjusted, and the Nd fraction was eluted using 3 M HNO(3). The method shows yields of about 90% or higher at pH 6 when the samples were buffered using ammonium acetate. Without the addition of buffer the yield decreased to below 80%. The isotopic composition of Nd in samples preconcentrated using Nobias PA1 agree within error with published data or data obtained by other methods. The total blank, including contributions from preconcentration, separation, and mass spectrometry, is estimated to be 0.2-0.4 pmol (30-60 pg) of Nd. The described preconcentration method, which can be used in the field, is easy, fast (about 8 h for a 3.6 kg sample), and reliable for preconcentration of Nd from a seawater matrix.     

Single-current-sensor-based active front-end-converter-fed four quadrants induction motor drive

Induction motor (IM) is a workhorse of the industry, whose dynamics can be modified close to that of a separately excited DC machine by field-oriented control technique, which is commonly known as vector control of induction machine. This paper presents a complete performance of the field-oriented control of IM drive in all four quadrants with a single-current-sensor-based active front end converter whose work is to regulate DC link voltage, draw pure sinusoidal currents at unity power factor and to facilitate bi-directional power flow between the grid and the drive. The entire system is completely modelled in MATLAB/SIMULINK and the results are discussed in detail. The vector control analogy of the back to back converters is highlighted along with the experimental results of field-oriented control of induction machine using a dsPIC30F6010A digital signal controller.     

Measurement of Nonlinear Phase Distortion in Microwave Limiters under Dynamic Conditions

Nonlinear phase distortion (amplitude-modulation to phase-modulation conversion) in microwave limiters can be different under static and dynamic conditions. A technique for measurement of dynamic phase distortion is described in which a two-tone test signal is used to simulate amplitude modulation with modulating frequencies of the order of megahertz. The two-tone test signal is generated by linearly summing two equal-amplitude sine waves. The result is a constant-frequency amplitude-modulated signal whose envelope varies as a rectified cosine wave at the beat frequency of the two sine waves. There is no phase deviation except at the envelope zeros, where the phase jumps 180°. Measurements are made by splitting the output signal from the limiter into two identical signals and delaying one relative to the other by approximately an odd multiple of one-half the envelope period. The two signals, when displayed on an X-Y cathode-ray tube, produce a pair of filled-in ellipses with major axes at 45° and and 135°. Peak phase deviation is obtained by direct measurement of either ellipse. Measurement data in E band are given for two tunnel-diode amplifier-limiters, a balanced mixer-limiter, and a traveling-wave-tube amplifier followed by a balanced mixer-limiter.     

Scatchard-Hildebrand热力学模型在PA印刷层迁移预测中的应用

目的探讨Scatchard-Hildebrand热力学模型对塑料印刷层中有害物质迁移分配系数预测的适用性和准确性。方法以聚酰胺(PA)印刷层中5种迁移物为代表,选取相关文献中PA印刷层中有害物质向不同模拟液中迁移的实验测试结果数据,对分配系数实验值Fexp与模型预测计算值Fsim作对比分析,并用实验数据对Scatchard-Hildebrand统计热力学模型进行校正,研究了模型修正系数Ks(Ks=ln(Fsim/Fexp))与迁移物相对分子质量(M)及其醇-水分配系数(log P)以及模拟液极性(Ps)间的关系。结果 PA印刷层中有害物质迁移分配系数的预测模型修正系数Ks与M和Ps间呈现显著的线性关系,得到了修正后的分配系数预测模型。结论修正后的Scatchard-Hildebrand热力学模型对预测塑料PA印刷层中有害物质迁移分配系数具有一定的适用性。     

Power factor definition in single phase system with arbitrary waveform according to similarity

Abstract

A new definition of power factor, which is suitable for an arbitrary waveform of voltage and current in a single‐phase system, is presented according to similarity between voltage and current waveforms. The similarity is described in infinite dimensions real vector space, and the power factor is defined as the multiplication of rootmean‐ square (RMS) value factor λ _RMS and phase factor λ_?. The new definition is compatible with IEEE Trial‐Use Standard 1459–2000, and can be a useful reference for power factor measurement, power factor correction and power compensation.     

Phase aberration correction in two dimensions with an integrateddeformable actuator/transducer

Two-dimensional arrays are required to implement two-dimensional phase aberration correction using traditional electronic correction techniques. A new transducer design, deformable in the elevation dimension, can be used to implement two-dimensional phase correction without using a full two-dimensional array. Phase correction in azimuth is achieved by altering the electronic phase delays of the elements. Phase correction in elevation is achieved by tilting the elements in elevation with piezoelectric actuators. Previously, such deformable arrays were fabricated by bonding PZT array elements to low frequency actuators. The construction of deformable arrays is simplified by using the actuator for both the element deflection and the generation of ultrasound. The new construction technique was used to fabricate a prototype 1×32 deformable array with a 3.5 MHz center frequency and an actuator flexure resonance of 3° at 1.3 kHz with a 300 Vpp sine wave. The prototype array was characterized and used to make B-scan images. Phase correction was simulated by tilting the elements on-line to alter the B-scan image and resulted in a cyst contrast reduction from 0.86 for the control to 0.76 with the elements tilted. Further characterization of the deformable array performance includes the frequency response of the actuator. Initial results from a 2×32 deformable array fabricated with the new construction technique are also presented. The 2×32 array configuration additionally offers the potential for on-line elevation focusing     

索引调制在水声通信中的应用及其研究进展

水声通信系统具有带宽受限和功率受限的显著特点。索引调制(Index Modulation, IM)技术在提高频谱效率、能源效率以及降低系统复杂度方面展现出了巨大潜力。因此,在过去的几年中,索引调制技术在水声通信中得到了广泛的应用,引起了国内外学者的普遍关注,有望成为高速水声通信系统的一个极具潜能的候选方案。文章聚焦于索引调制相关技术在水声通信中的应用,并对其性能进行分析,总结其研究进展。     

Integrated sub-harmonically pumped up-converter antenna for spatial power combining

A Ka-band sub-harmonically pumped up-converter antenna employing the substrate integrated waveguide (SIW) technique is proposed and used to realise a low-cost transmitter together with spatial power combining architecture in this paper. A single Ka-band sub-harmonically pumped up-converter using SIW band-pass filter is developed, exhibiting a conversion loss of about 7 dB. Based on the designed up-converter and SIW feeding antipodal linearly tapered slot antenna (SIW-ALTSA), the integrated up-converter antenna is designed and fabricated. Measured results of equivalent isotropic radiated power (EIRP) and radiation patterns are given. Finally, a 2 x 2 up-converter antenna array is designed and fabricated. Measured result shows the array has a power combining efficiency of above 90% and IM3 EIRP of 16 dBm. In close-range point-to-point communication and radar systems, the demonstrated millimetre-wave sub-harmonically pumped up-converter antenna array can be considered as a transmitter because of its low cost, high dynamic range and high linearity.     

A simple and effective load-pull system for RF power transistorlarge-signal measurements for wireless communication power amplifierdesign

Conventional load-pull methods for RF power transistor large-signal measurements usually need complicated RF measurement instrumentation. A simple load-pull measurement setup and a test procedure with IEEE-488 GPIB control and data acquisition capability has been developed. This is used to facilitate the design of an RF power amplifier (PA) for wireless communication applications. Compared with the conventional load-pull method, it is simpler and less costly, yet effective. Measured examples of Siemens GaAs FET's CLY-2 and CLY-10, which are used to design a RF PA module for ISM-band (902-928 MHz) wireless communications, are presented     

Third-order parametric array generated by distantly spaced primary ultrasonic tones

Traditional parametric arrays are produced by a second-order nonlinear interaction between two primary ultrasonic tones that are close in frequency, resulting in a difference tone that is in the audio band. This article presents a parametric array produced by a third-order nonlinear interaction between two primary ultrasonic tones that are distantly spaced in frequency such that one tone is approximately the second harmonic of the other. The result is a third-order lower intermodulation (IM3) tone in the audio band with greater directivity and lower side lobe amplitude than comparable second-order fields. Measurements are presented that compare the directivity of 1-, 2-, and 4-kHz difference tones to that of 1-, 2-, and 4-kHz IM3 lower tones. Furthermore, a cascaded second-order approach for N-element transducer arrays is used to model third-order scattering with good agreement between measurement and theory.     

Automated Signal Generator Level Characterization and Verification

Automatic test systems are described that are used to characterize and verify the output level performance of signal generators using internally stored correction data applied under microprocessor control. The characterization technique allows user verification of output level performance by direct measurement with a conventional power meter. Particular emphasis is given to a level verification system capable of measuring output power from +20 dBm to less than -140 dBm in a frequency range of 100 kHz to 2.5 GHz with an uncertainty of less than 1 dB. An analysis of error factors and actual performance data is presented.     

Comparison of K_(IC) Values for SiC Whisker Reinforced Ceramic Composites Obtained by Using Various Methods

The fracture toughness (KIC) values determined by indentation microfracture method (IM ) for SiC whisker reinforced Al2O3 and ZrO2 based composites were calculated with different IM equations and compared with those obtained by singte edge notched beam (SENB) technique. Experimental results show that the KIC (IM) values calculated with different equations are quite different one from another. For composites without phase transformable components the KIC (IM) and KIC (SENB) values are practically on the same level, but for composites with phase transformable components (partially stabilized zirconia) the KIC (SENB) values are always higher than KIC (IM). This is because that the IM method can not reveal sensitively the toughening effect due to dynamic t-m transformation of ZrO2 as the SENB method does. The accuracy of the IM method depends on the Suitability of the IM equations and was evaluated for the materials used in this investigation. Two new IM equations are suggested with which the KIC (IM ) values can be obtained very close to KIC (SENB) values for composites having phase transformable components.     

Selecting Test Frequencies for Two-Tone Phase-Plane Analysis of ADCs: Part II

A method for selecting test frequencies for two-tone phase-plane modeling of ADCs is given. The results here include and generalize the results of a previous paper on the subject. The new results show how to select a good frequency pair that is near any two specified frequencies. An error analysis is given showing how close the actual test frequencies must be to their ideal values to maintain near-optimal phase-plane coverage.     

Vibration of multilayered beams using sinus finite elements with transverse normal stress

A family of sinus models is presented for the analysis of laminated beams in the framework of free vibration. A three-noded finite element is developed with a sinus distribution with layer refinement. The transverse shear strain is obtained by using a cosine function avoiding the use of shear correction factors. This kinematic accounts for the interlaminar continuity conditions on the interfaces between the layers, and the boundary conditions on the upper and lower surfaces of the beam. A conforming FE approach is carried out using Lagrange and Hermite interpolations. It is important to notice that the number of unknowns is independent of the number of layers. Vibration mechanical tests for thin and thick laminated and sandwich beams are presented in order to evaluate the capability of these new finite elements to give accurate results with respect to elasticity or finite element reference solutions. Both convergence velocity and accuracy are discussed and these new finite elements yield very accurate results at a low computational cost for various boundary conditions. In particular, the two models including the transverse normal effect have the capability to take into account the thickness mode shape.     

Frequency-modulation spectroscopy with blue diode lasers

Frequency-modulation spectroscopy provides ultrasensitive absorption measurements. The technique is especially adaptable to diode lasers, which can be modulated easily, and has been used extensively in the near-infrared and infrared spectral regions. The availability of blue diode lasers now means that the accessible wavelength region can be increased. We successfully demonstrate wavelength-modulation spectroscopy and two-tone frequency-modulation spectroscopy for the weak second resonance line of potassium at 404.8 nm and for the transition at 405.8 nm in lead, starting from the thermally populated 6(p)(2 3)P(2) metastable level. Information on the modulation parameters is obtained with a fitting procedure. Experimental signal-to-noise ratios at different absorption levels are compared with theoretical signal-to-noise ratios and show good agreement. Detection sensitivities of 2 x 10(-6) and 5 x 10(-6) for wavelength and two-tone frequency-modulation spectroscopy, respectively, for a 120-Hz bandwidth are demonstrated.     

基于矢量误差修正的实时负载牵引测量模型方法

提出了一种新型基于矢量误差修正的负载牵引测量模型方法。相比于传统负载牵引测量系统,该方法从8-term矢量误差模型入手,建立接收机与被测件端口处电压波的函数关系,通过对矢量网络分析仪进行矢量校准和对内部接收机进行一次绝对功率校准,可实时测量被测件的输入/负载反射系数,输入/输出功率及功率增益、效率等。按照模型方法搭建了相应的硬件系统,与商用Focus的类似系统进行了比较验证,实验结果表明具有良好的效果,证明了所提方法的准确性。     

Aperture Proximity Effects in High Heat Flux Sensors Calibration

In the transfer calibration of heat flux sensors, a correction for the irradiance distribution across the sensing area may be required when the sensing areas of the reference and test sensors are different. A method to calculate this correction using well-known equations for the configuration factors is presented. Also, estimates of the correction for test conditions corresponding to the transfer calibration technique in use at the National Institute of Standards and Technology are given.