Carbon Nanotube Based Multifunctional Ambipolar Transistors for AC Applications

Field‐effect transistors (FETs) fabricated on large diameter carbon nanotubes (CNTs) present typical ambipolar transfer characteristics owing to the small band‐gap of CNTs. Depending on the DC biasing condition, the ambipolar FET can work in three different regions, and then can be used as the core to realize multifunctional AC circuits. The CNT FET based circuits can work as a high‐efficiency ambipolar frequency doubler in the ambipolar transfer region, and also can function as in‐phase amplifier and inverted amplifier in the linear transfer region. Due to current saturation of the CNT FET, an AC amplifier with a voltage gain of 2 is realized when the device works in the linear transfer region. Achieving an actual amplification and frequency doubling functions indicates that complicated radio frequency circuits or systems can be constructed based on just one kind of device: ambipolar CNT FETs.     

分压-自偏压共源放大电路的Multisim仿真研究

针对场效应管电路分析中不同元件性能参数不同而导致一些理论计算复杂、繁琐,并且难于理解的情况,通过对N沟道增强型MOS场效应管组成的分压-自偏压共源放大电路的理论研究,利用Multisim仿真软件对电路实际工作情况进行模拟,根据二者结果的对比,研究并提出了分压-自偏压共源放大电路的Multisim电路仿真研究的方法。     

Large-signal criteria for the design of GaAs FET distributed power amplifiers

An analysis of the GaAs FET distributed network for power amplification shows that the principal circuit values and performance characteristics can be expressed in terms of the GaAs FET large-signal voltages, currents, and power per millimeter of gate width, together with the required power and bandwidth only. The method is useful as a first design step in which the FET structure and distributed network are designed together to realize a monolithic traveling-wave power amplifier.     

2-20-GHz GaAs Traveling-Wave Power Amplifier

Power amplification in FET traveling-wave amplifiers is examined, and the mechanisms which limit power capability of the amplifier are identified. Design considerations for power amplification are discussed. A novel single-stage and two-stage monolithic GaAs traveling-wave power amplifier with over 250-mW power output in the 2-20-GHz frequency range is described.     

A monolithically integrated AlGaAs/GaAs p-i-n/FET Photoreceiver by MOCVD

An AlGaAs/GaAs p-i-n photodiode and a GaAs FET have been monolithically integrated on a GaAs substrate by using the metal-organic chemical vapor deposition (MOCVD) technique and by applying a new interconnection technique. A current amplification characteristic consistent to the device parameters has been demonstrated. This result indicates a suitability of MOCVD to realize the monolithic integration of p-i-n/FET photoreceiver.     

Polarization-agile microstrip antenna array using a single phase-shift circuit

A novel polarization-agile microstrip antenna array is proposed, in which the polarization agility from linear to circular polarization for the whole array is realized easily by controlling a single phase-shift circuit. Using the corner-fed square patch element, a new 16 element dual-polarized array with high isolation and low cross-polarization is designed and analyzed by the extended multiport network method. A special FET phase shifter circuit is created, where 0/spl deg/ or 90/spl deg/ phase shift between dual ports is electrically switched. Experimental results are presented to verify the theory, and measured circularly-polarized radiation patterns show a boresight axial ratio of 0.5 dB. Another experiment that connects a low noise amplifier together with the phase-shift circuit is also introduced, realizing both polarization agility and power amplification with one active circuit.     

一种新型极化捷变有源微带天线阵

本文提出了一种新颖的极化捷变放大器型有源微带天线阵,只要在馈电端电控单一有源电路就能实现整个微带天线面阵极化的捷变和信号的放大.利用角馈方形微带贴片设计了一副具有高隔离度和低交叉极化的新颖16元双极化面阵,并分析了天线阵的共极化和交叉极化方向图.介绍了有源电路的设计.该电路利用一专用电控移相器,通过改变场效应管(FET)栅极的直流控制电压,电控两极化端口间的0°或90°相差,实现天线阵由线极化到圆极化的捷变.低噪声放大器(LNA)不仅使有源天线增益提高12-14dB,而且改善了天线的驻波比带宽和隔离度.文中给出了无源双极化阵和有源阵的实验结果,证实了理论的有效性.     

Analysis of noise up-conversion in microwave field-effecttransistor oscillators

The conversion process of the low frequency noise into phase noise in field-effect transistors (FET) oscillators is investigated. First, an evaluation of the baseband noise contribution to the oscillator phase noise is provided from the analysis of the baseband noise and the frequency noise spectra. A distinction is made within the different components of the low frequency noise contributions to close-in carrier phase noise. Next, the frequency noise of the oscillator circuit is analyzed in terms of the FET's low frequency noise multiplied by the oscillator's pushing factor. Though this product usually provides a good evaluation of the phase noise, experimental results presented here show the inaccuracy of this method at particular gate bias voltages where the pushing factor decreases to zero. To account for these observations, a new nonlinear FET model involving at least two noise sources distributed along the channel is proposed     

A vertical FET with self-aligned ion-implanted source and gate regions

A new self-aligned vertical channel JFET has been fabricated using ion-implantation and LOCOS techniques. This device required four photolithography processes. Fine patterning and accurate mask alignment are not required by this process. The electrical properties of this device are a voltage amplification factor of more than 5, a source-to-gate breakdown voltage of 50 V, and a drain-to-gate breakdown voltage of 140 V. It is possible to realize a larger voltage amplification factor, compared to the diffused vertical FET.     

行波场效应器件的耦合模作用原理

本文提出一个用增加电极长度来提高微波场效应器件输出功率的新方法。从一个具有分布参数的电极系统模型出发,求得一组描述电极系统上电流电压与半导体中的电荷流的相互作用方程,这些基本方程以耦合模的形式表示。本文讨论了弱耦合情况下的行波放大特性。在同步工作时,增益具有极宽频特性,波幅沿漏极线上线性增长,功率输出正比于电极的有源长度,并具有宽频功率合成特性。在异步工作时,增益变为低频窄带特性。当系统的电磁耦合存在时,系统中的波幅沿线路近似地按指数增长,并具有高增益特性。在合适的电极系统设计下,行波场效应器件是可以实现大功率输出,长寿命工作的。     

A Compact Broad-Band Multifunction ECM MIC Module

A development effort is described that yielded a compact broad-band ECM module using soft and hard substrate material employing microstrip, slotline, and coplanar line. Integrated functions include coupling, limiting, upconversion, downconversion, broad-band amplification, amplitude modulation, switching, gating, and stable frequency generation. A high-level frequency converter with a + 28-dBm intercept point resulted in high dynamic range, spurious-free operation (--45 dBc). Extremely flat amplification with low-current drain is achieved with distributed and cascode FET amplifiers at S - C and X-bands.     

A minaturized broad-band MMIC frequency doubler

A miniaturized broadband balanced MMIC (monolithic microwave integrated circuit) frequency double, composed of a common-gate FET and a common-source FET directly connected to each drain electrode, has been proposed and demonstrated. The doubler is designed and fabricated as a miniaturized function module using a conventional two-gate FET configuration, active trapping, and active impedance matching. The doubler design has been performed through phase error estimation, gate width optimization, and gate-source voltage optimization. The phase error estimation in a nonlinear condition has eliminated phase error compensation circuits. The fabricated chip size is only 0.5 mm×0.5 mm, which is about 1/10 the area of previously reported doublers. A conversion loss of 8-10 dB, a fundamental frequency suppression better than 17 dB, and an input return loss better than 8 dB are obtained in the output frequency range from 6 to 16 GHz. The broadband doubler as a miniaturized MMIC function module can be applicable to small-size oscillator MMICs and multifunction MMICs     

A performance comparison of two p-i-n FET receiver circuit architectures

Two conceptually different p-i-n FET receiver circuit architectures are evaluated using a SPICE circuit simulation. The popular p-i-n FET transimpedance amplifier is compared to a new architecture that uses distributed gain and dual feedback. To highlight the importance of circuit architecture to receiver performance, identical device parameters are used in each circuit model. Frequency, phase, and pulse responses are computed and presented in graphical form. Results demonstrate that the popular receiver is adversely sensitive to FET transconductance variations and distorts the pulse reponse, whereas the distributed gain and dual feedback design is substantially independent of transistor parameters and free of pulse distortion.     

X-Band Low-Noise GaAs Monolithic Frequency Converter (Short Paper)

An X-band, low-noise GaAs monolithic frequency converter has been developed. Multicircuit functions, such as amplification, filtering, and mixing, were integrated on to a single GaAs frequency converter chip. The frequency converter consists of an X-band three-stage low-noise amplifier, an image rejection filter, an X-band dual-gate FET mixer, and an IF-band buffer amplifier. To minimize circuit size without degrading performances, an RC-coupled buffer amplifier was connected directly after a dual-gate FET mixer IF port, and one-section parallel and series microstrip lines were adopted for the amplifier. One-half-micron (1/2 µm) single-gate FET's and a one-micron (1 µm) dual-gate FET, which have an ion-implanted closely-spaced electrode structure, were used. Either via hole grounds or bonding wire grounds are selectable for the frequency converter. Chip size is 3.4x1.5 mm. The frequency converter provides less than 3-dB noise figure and more than 34-dB conversion gain.     

A performance comparison of two p-i-n FET receiver circuit architectures

Two conceptually different p-i-n FET receiver circuit architectures are evaluated using a SPICE circuit simulation. The popular p-i-n FET transimpedance amplifier is compared to a new architecture that uses distributed gain and dual feedback. To highlight the importance of circuit architecture to receiver performance, identical device parameters are used in each circuit model. Frequency, phase, and pulse responses are computed and presented in graphical form. Results demonstrate that the popular receiver is adversely sensitive to FET transconductance variations and distorts the pulse reponse, whereas the distributed gain and dual feedback design is substantially independent of transistor parameters and free of pulse distortion.     

Compensation of parasitic source capacitance in an FET differential amplifier

The amplitude and phase responses and high-frequency stability of an FET differential amplifier can be improved by compensating the parasitic source capacitance with a small capacitor between the gate and source of the input FET. This provides a significant improvement in the performance of oscillators and tuned or wideband amplifiers.     

Wave Propagation on MESFET Electrodes and its Influence on Transistor Gain

A rigorous analysis of wave propagation along MESFET electrodes is presented. Both the losses caused by the channel and those caused by the finite electrode conductivity are included, together with small-signal amplification. Results from this wave analysis are used to determine overall gain. Conclusions concerning traveling-wave FET design, optimal gate width and related criteria are drawn.     

The characteristics and applications of a V-shaped notched-channel field-effect transistor (VFET)

A new junction field-effect transistor (FET) structure with a V-shaped notched channel fabricated by preferential etching of 〈100〉 silicon is described. This transistor (VFET) exhibits a higher maximum transconductance and a lower turn-on resistance than a conventional FET with the same surface dimensions. The fabrication procedures for a p-n junction gate as well as a Schottky barrier gate device are outlined. A first order model for the VFET is discussed. Experimental results are presented and are shown to be in agreement with the predictions of the model. The advantages of the VFET (with Schottky barrier and/or p-n junction gates) for analog switching, microwave frequency amplification and integrated circuits are discussed. Modifications of the basic VFET structure to obtain other useful functions are also described.     

Novel active FET circular patch antenna arrays for quasi-opticalpower combining

This paper discusses two-dimensional planar arrays of weakly coupled active circular patch antennas suitable for quasi-optical power combiners. A novel radiating element that has low cross-polarization is described. A two-dimensional array analysis was developed to address radiation pattern and phase problems. Equivalent isotropic radiated power levels of 1.5 W for a two by two FET array and 3.8 W for a two by four FET array have been obtained at X-band     

GaAs Dual-Gate FET for Operation Up to K-Band

A high-frequency equivalent circuit model of a GaAs dual-gate FET and analytical expressions for the input/output impedances, transconductance, unilateral gain, and stability factor are presented in this paper. It is found that the gain of a dual-gate FET is higher than that of a single-gate FET at low frequency, but it decreases faster as frequency increases because of the capacitive shunting effect of the second gate. A dual-gate power FET suitable for variable gain amplifier applications up to K-band has been developed. At 10 GHz, a I.2-mm gatewidth device has achieved an output power of 1.1 W with 10.5-dB gain and 31-percent power-added efficiency. At 20 GHz, the same device delivered an output power of 340 mW with 5.3-dB gain. At K-band, a dynamic gain control range of up to 45 dB was obtained with an insertion phase change of no more than +-2 degrees for the first 10 dB of gain control.