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     

Comparison of phase noise simulation techniques on a BJT LC oscillator

The phase noise resulting from white and flicker noise in a bipolar junction transistor (BJT) LC oscillator is investigated. Large signal transient time domain SPICE simulations of phase noise resulting from the random-phase flicker and white noise in a 2 GHz BJT LC oscillator have been performed and demonstrated. The simulation results of this new technique are compared with Eldo RF and Spectre RF based on linear circuit concepts and experimental result reported in the literature.     

A cryogenic system for RF measurements on superconducting vortexflow transistors

A scheme for measuring the RF properties of the superconducting vortex flow transistor (VFT) is presented. This scheme features a low-crosstalk RF launcher with solderless contacts, a cryogenic system that permits room temperature access in close proximity to the VFT, and a circuit configuration that allow vector S-parameter measurements at power levels below -90 dBm     

双极型光栅晶体管的瞬态特性模型及模拟分析

提出一种应用于CMOS图像传感器的新型光电检测器件-双极型光栅晶体管，并建立了其瞬态等效电路模型，利用电路模拟软件HSPICE的多瞬态分析法对双极型光栅晶体管的光电流特性进行了仿真，分析得出这种新型器件在0.6μmCMOS工艺参数下，由于引入pn注入结加速了光电荷的读出速率，光电流随外加电压呈指数式增长，与普通光栅晶体管相比，蓝光响应特性有较大改善。     

Residual phase noise measurements of VHF, UHF, and microwavecomponents

The results of residual phase noise measurements on a number of VHF, UHF, and microwave amplifiers, both silicon (Si) bipolar junction transistor (BJT) and gallium arsenide (GaAs) field effect transistor (FET) based, electronic phase shifters, frequency dividers and multipliers, etc., which are commonly used in a wide variety of frequency source and synthesizer applications are presented. The measurement technique has also been used to evaluate feedback oscillator components, such as the loop and buffer amplifiers, which can play important roles in determining an oscillator's output phase noise spectrum (often in very subtle ways). While some information has previously been published related to component residual phase noise properties, it generally focused on the flicker noise levels of the devices under test, for carrier offset frequencies less than 10 kHz. The work reported herein makes use of an extremely low noise, 500 MHz surface acoustic wave resonator oscillator (SAWRO) test source for residual phase noise measurements, both close-to-and far-from-the-carrier. Using this SAWRO-based test source at 500 MHz, we have been able to achieve a measurement system phase noise floor of -184 dBc/Hz, or better, for carrier offset frequencies greater than 10 kHz, and a system flicker phase noise floor of -150 dBc/Hz, or better, at 1 Hz carrier offset. The paper discusses the results of detailed residual phase noise measurements performed on a number of components using this overall system configuration. Several interesting observations related to the residual phase noise properties of moderate to high power RF amplifiers, i.e., amplifiers with 1 dB gain compression points in the range of +20 to +33 dBm, are highlighted     

Measurement of discrete charge in the systems of ultra-small tunnel junctions

The measurement of a charge of an almost isolated metal island gives discrete values. The non-equilibrium quantum effects on the shape of transition between these discrete values are studied here. They were shown to determine the width of transition in the limit of small temperatures and junction conductivities. Since any real measurement sets the system to non-equilibrium state the result of measurement is determined by properties of a measuring device. The most practical cases are discussed below: measurements by Fulton-Dolan electrometer as well as by co-tunneling electrometer and self-measurement of the charge by the SET transistor. The results obtained seem to be of general importance for non-equilibrium dissipative quantum dynamics.     

Comments on “A highly linear single p-n junction temperaturesensor”

The concept of using switched currents through a single p-n junction for a linear temperature measurement as proposed by Freire et al. (Apr. 1994) has been previously described by J. Williams (1991). Williams uses asynchronous set of switches (LTC 1043) to switch separate currents through a diode-connected transistor, and also to switch capacitors synchronously with the currents. This action creates an output that is proportional to the peak-to-peak voltage of the sensor. The circuit uses relatively few components. There are, however, some design errors in the the current generator that he uses. It was pointed out to Williams that trimming is necessary due to component tolerances, and a simpler and more accurate means of generating the two selected currents was proposed (May 1991)     

A five-port deembedding method for floating two-port networks

Radio frequency (RF) high-power bipolar transistors are often constructed with the collector accessible at the bottom of the device. Characterization is carried out on substrate mounted devices. The classical methods developed for the “on wafer” capacitance-voltage (CV) and alternating current (ac) measurement of grounded devices are then no longer applicable. A (general) deembedding algorithm is presented in which the medium surrounding the transistor is taken to be a generic five port and the transistor is treated as a floating two port. Using this approach, one can model a wide variety of configurations, including coupled lines, bondwire complexes with mutual coupling, vies and packages enabling one pass deembedding. Use of this algorithm facilitates an integrated approach improving accuracy and speed. Implementation of the five-port algorithm in HP's-microwave design software, MDS, and HP's parameter extraction software, IC-CAP as well as its application to high-frequency power transistor modeling are described     

Tunable ferroelectric capacitor-based voltage-controlled oscillator

Ferroelectric capacitors made from Ba(1-0.5)Sr0.5TiO3 (BST) are applied as varactors in tunable, high-frequency circuit applications. In this context, a voltage-controlled oscillator (VCO) has been designed and implemented using discrete RF bipolar junction transistor (BJTs) and tunable ferroelectric capacitor. The designed VCO has a tuning range from 205 MHz to 216.3 MHz with a power dissipation of 5.1 mW. The measured phase noise is -90 dBc/Hz at 100 kHz and -140 dBc/Hz at 1 MHz offset.     

Effect of emitter current on the properties of the collector junction in silicon and germanium transistor structures

We have studied the effect of emitter current on the capacitance of a forward-biased collector junction in silicon and germanium transistor structures. The results demonstrate that nonequilibrium carriers in the collector junction at a nonzero emitter current are responsible for an additional capacitance and facilitate conversion of the net capacitance of the collector junction to an inductance (negative capacitance). Therefore, both the magnitude and sign of the collector capacitance can be controlled by varying the emitter current. Experimental evidence is presented that, at high emitter currents, the barrier capacitance of the collector junction in the transistor structures may both increase and decrease, depending on the nature of the junction and the doping levels in the base and collector regions. Our experimental data agree well with calculation results.     

Effects of surface treatments using PECVD-grown hexamethyldisiloxane on the performance of organic thin-film transistor

Hexamethyldisiloxane (HMDSO) was deposited on a gate dielectric surface by plasma enhanced chemical vapor deposition for surface treatment, and its effects on the microstructure of pentacene and the transistor characteristics were examined. HMDSO films were deposited at room temperature at various RF powers (10 W to 120 W). Atomic force microscopy analysis of the pentacene films showed a significant increase in the grain size of the samples treated under the optimum RF power (10 W), which in turn led to a significant improvement in the electrical mobility. These results show that PECVD-grown HMDSO can be used as an effective surface treatment and warrants further investigation for process optimization.     

Virtual instrument for instantaneous power measurements

A computer-based data acquisition system coupled by means of a general-purpose instrumentation bus (IEEE488/GPIB) with a digital oscilloscope is used to create a virtual instrument with instantaneous and average power measurement capability. The software signal-processing capability of the data acquisition system was used to compensate instrument measurement deficiencies and to enhance signal capture. The virtual instrument is shown to provide instantaneous, AC, and fitted-power averages and time-based plots of power variations for both linear and nonlinear system responses to external excitation. Data taken on a resistor, capacitors, an AC-to-DC power converter, and a bipolar junction transistor inverter establish a ±3% sensitivity with a 10-μW-100-W range over a 1-Hz-10-MHz frequency span     

Autonomous Sensor System With Power Harvesting for Telemetric Temperature Measurements of Pipes

In this paper, an autonomous sensor system, with low-power electronics for radio-frequency (RF) communication, incorporating a thermoelectric energy-harvesting module for unattended operation is presented. A target application is proposed for temperature measurement of walled-in pipes. When the autonomous sensor is placed on the heat source, a thermoelectric module harvests energy, powering the autonomous sensor. In this condition, no external power source is necessary, the temperature measurement is performed, and the data are saved into a nonvolatile memory. When the external readout unit is active, the electromagnetic field is used to power the autonomous sensor system and to communicate the data. An experimental setup has been arranged and characterized by measuring the temperature along the pipe, the voltage that can be generated by thermoelectric generators, and the influence of different materials on RF communication. The temperature data of the heat source, which are collected by the autonomous sensor, are compared with that of a reference thermistor. The measurement results show good agreement between the two measured temperature data sets. The experimental data demonstrate that the autonomous system works correctly for a temperature gradient that is higher than 9degC, within a readout distance of a few centimeters. The presented autonomous sensor system can be effectively used for measurements into a close environment in which a temperature difference is present.     

Fabrication and radio frequency characterization of carbon nanotube field effect transistor: evidence of quantum capacitance

We fabricated an radio frequency (RF) carbon nanotube field effect transistor (CNTFET) whose electrode shapes were standard RF designed ground-signal-ground (GSG)-type pads. The S-parameters measured from our RF CNTFET in the frequency range up to 6 GHz were fitted with an RF equivalent circuit, and the extracted gate capacitance was shown to be the capacitance value of the series combination of the electrostatic capacitance and the quantum capacitance. The effect of the channel resistance and the kinetic inductance was also discussed.     

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     

Fabrication and Characteristics of Self-Aligned Dual-Gate Single-Electron Transistors

Single-electron transistors that have electrical tunneling barriers are fabricated, and Coulomb oscillation peaks and negative differential transconductance are observed at room temperature (300 K). Operation characteristics and multioscillation peaks are further investigated at low temperature (80 K). The period of Coulomb oscillation is 2.3 V due to an ultrasmall control gate capacitance, and oscillation peaks are shifted through the side gate bias, which is explained by the derived stability plot for dual-gate structures. Even with the side gates electrically floating, the device still operates as a single-electron transistor since the p-n junction barrier plays a role of tunneling barrier. In addition, by changing the bias condition, double dots are formed along the channel and peak splitting is observed.     

A Method to Evaluate the Second Breakdown Resistance of Power Transistors

A new evaluation method of forward-biased second breakdown resistance in power transistors employing a characteristic variation of current gain is presented. Predictions for second breakdown resistance in power transistor are made by monitoring the changing point of the base current at the collector-base junction under the constant voltage and constant current conditions. This characteristic phenomenon which is related to the variation of the current gain is dependent on the temperature and current density at a localized spot of the transistor. It is concluded that the time delay required to reach the changing point of the base current can be considered as a measure of the second breakdown resistance. The forward-biased second breakdown resistance can be measured without damage or degradation of the sample transistors, if the supplied power is removed before the base current reaches the changing point.     

Driver circuits for temperature-invariant performance of junction diodes

Different types of driver circuits for the temperature-invariant brightness of light emitting diodes and the RF performance of Schottky barrier diodes, p-i-n diodes and p-n junction diodes are presented. The sensitivities of the proposed driver circuits with ambient temperature, bias voltage and other component variations are presented. Novel techniques are proposed and demonstrated to compensate the performance variation of diode-based circuits due to the temperature sensitivity of the components of driver circuits. The proposed driver circuits eliminate the requirement of conventional temperature compensation techniques with temperature sensors. The driver circuits respond directly to the junction temperature of the diodes itself; thus, there will be no compensation error due to the temperature gradient or self-heating of the diodes. This technique is very simple, accurate and easy to implement.     

In-Circuit Transistor Leakage Current Testing

An instrument capable of measuring leakage current of transistors while the trarisistor remains in the circuit was developed. This instrument gives an accurate leakage current measurement in a large variety of circuits as well as being simple to operate, lightweight, battery powered, and portable for use in the field. This was accomplished by the measurement of the transistor leakage current ICBX, which is the collector current when both the collector and emitter junctions of the transistor are reverse biased. This particular leakage current was chosen because it is nearly independent of the gain parameters of the transistor and a very close approximation to the fundamental leakage current ICBO. The present instrument measures leakage currents as low as 1 ?a with a collector load resistance down to 500 ?. At present, an accurate instrument is not commercially available for measuring transistor leakage current in the circuit. The results presented in this paper indicate a method for adding the capability of measuring in-circuit transistor leakage current to future transistor testers.