An Experimental Gyro-TWT

Three experimental gyro traveling wave tubes (TWT'S) have been built and tested. All tubes used a fundamental cyclotron resonance interaction with the circularly polarized TE/sup 0/sub 11/ dominant waveguide mode. The tubes differed in the length of the single circuit section and in the amount of distributed loss used. The experiments were conducted at 5 GHz, with the object of producing a design that could be scaled to 94 GHz. Results on the third experiment include measurements of stable gain as high as 24 dB small signal and 18 dB saturated. A saturated power output of 120 kW at a total beam efficiency of 26 percent was measured with a 3-dB saturated power output bandwidth of 6 percent. The design features of the tubes and the experimental results are described fully.     

Theoretical power output and bandwidth of traveling-wave amplifiers

Expressions are developed to calculate the theoretical power output of traveling-wave amplifiers using any type of RF structure. Calculations are made for helix-type tubes and it is shown how to calculate the power output of tubes using more dispersive structures in terms of calculations made for helix tubes. The principal factors accounting for higher power output of dispersive structures are presented and discussed. The gain and bandwidth of forward-wave helix amplifiers are derived from the small-signal theory as functions of frequency and it is shown that the gain in db times the frequency bandwidth is a constant as a function of helix length for highgamma_{0}a'and the gain times the bandwidth squared is a constant for lowgamma_{0}a'.     

A Low-Power CMOS Linear-in-Decibel Variable Gain Amplifier With Programmable Bandwidth and Stable Group Delay

This brief presents a new circuit architecture for linear-in-decibel, constant-bandwidth variable gain amplifier (VGA). To obtain high linearity under low-voltage operation, this VGA is a closed-loop structure. In loop amplifier design, two techniques are applied: first, the loop amplifier is given finite input impedance. This arrangement keeps the VGA bandwidth constant under different gain setting. Second, a current-buffered compensation is applied for loop stability. Compared to the Miller compensation, this method achieves wider bandwidth. The prototype chip using 0.18-mum CMOS technology demonstrates that -10- to 20-dB gain and 0.5- to 30-MHz bandwidth can be programmed independently. The group delay difference within 30-dB gain control range is smaller than 1%. The total circuit dissipates 1.35 mA from a 1.8-V supply     

A design technique for a high-gain, 10-GHz class-bandwidth GaAsMESFET amplifier IC module

A design procedure is proposed for a high-gain and wideband IC module, using stability analysis and a unified design methodology for ICs and packages. A multichip structure is developed using stability analysis and the requirements for stable operation are determined for each IC chip, package, and interface condition between them. Furthermore, to reduce the parasitic influences, several improvements in the interface and package design are clarified, such as wideband matching and LC resonance damping. IC design using effective feedback techniques for enlarging the bandwidth are also presented. The ICs are fabricated using 0.2-μm GaAs MESFET IC technology. To verify the validity of these techniques, an equalizer IC module for 10-Gb/s optical communication systems was fabricated, achieving a gain of 36 dB and a bandwidth of 9 GHz     

A Reflected-Wave Ruby Maser with K-Band Tuning Range and Large Instantaneous Bandwidth

A novel maser concept is outlined and a unique design described which permits wide bandwidth and waveguide tuning range by employing four stages cascaded via cryogenically cooled circulators. Theoretical considerations for gain, bandwidth, gain ripple, and noise temperature are included. Operated on a chased-cycle helium refrigerator with a superconducting persistence-mode magnet, the four-stage amplifier is tunable from 18.3 to 26.6 GHz with 30 dB of net gain and achieves 240 MHz of 3-dB bandwidth near the center of this band. The measured noise temperature is 13/spl plusmn/2 K referred to the room-temperature input flange. Applications are foreseen utilizing cooled parametric downconverters and upconverters with this amplifier at IF to extend the low-noise performance up to millimeter frequencies and down to L-band for radio astronomy and planetary spacecraft communication.     

A Design and Packaging Technique for a High-Gain, Gigahertz-Band Single-Chip Amplifier

Equalizing amplifiers for gigabit optical fiber transmission systems requires a 65-dB gain (S21) with a gigahertz bandwidth. However, this gain has the potential to cause significant parasitic oscillation. Consequently, developing a useful stabilization design technique is a very important factor in attaining practical design. In this paper, stabilization design techniques are described for circuit configurations, packaging, and stability assessment. In addition, fabrication results of amplifier IC based on bipolar super self-aligned process technology (SST) and new wide-band high isolation package with coaxial-like 50-/spl Omega/ signal lines are also shown. A 65-dB gain, 1.3-GHz bandwidth single-chip amplifier has been successfully fabricated.     

Design and performance of transferred electron amplifiers using distributed equalizer networks

This paper describes improved techniques for the design of broad-band linear reflection-type microwave amplifiers using transferred electron devices. These techniques have produced excellent agreement between amplifier design goals and performance. This agreement results from improvements in measuring techniques and data reduction in addition to the use of a distributed equalizer topology. Multistage amplifiers having a net gain of over 25 dB and a power output in excess of 0.4 W over a bandwidth of 4 GHz in X- band have been realized.     

A Binary-Weighted Switching and Reconfiguration-Based Programmable Gain Amplifier

In previous works, the authors reported on binary-weighted switching and reconfiguration techniques to design programmable gain amplifiers (PGAs) with a wide decibel (dB)-linear range, a small gain error, a wide 3-dB bandwidth, and high linearity. In this brief, two techniques are analyzed in more detail. Adopting the two techniques, a new low-voltage PGA version is proposed that offers a precise and process/temperature-insensitive gain and achieves a double dB-linear range with a small gain error while maintaining the same chip size, as compared with those of previous designs. Implemented in 0.18-mum CMOS, from the measurements, the proposed PGA shows a dB-linear gain range of 42 dB (-21 to 21 dB) with a gain error of less than plusmn 0.54 dB, a maximum input-referred third-order intercept point (IIP3) of 14 dBm, and a 3-dB bandwidth of 60 MHz at the maximum gain while consuming only 2.1 mA from a 1.5-V supply.     

The Coupled-Cavity Transmission Maser- Engineering Design

The experimental design of an X-band microwave maser amplifier which uses a new type of slow-wave circuit is described. A detailed theoretical analysis of the circuit is presented in a companion paper. The slow-wave circuit consists of a cascade of iris-coupled ruby resonators separated by garnet isolators. This unit provides significant reduction in size and weight over previously reported maser slow-wave circuits. The microwave properties of the solid ruby resonator are treated in detail, and the passive bandwidth of the single transmission cavity and its relation to the iris susceptance are shown. Experimental techniques involved in obtaining and measuring precise iris susceptance are presented. A step-by-step procedure for designing an amplifier having a given gain and tuning range is also presented. Typical performance characteristics include a gain of 30 db, instantaneous bandwidth of 25 Mc and a noise temperature of 15/spl deg/K. An electronic tuning range of 200 Mc has been achieved in one configuration with a 20 db gain and a 25-Mc bandwidth. The weight of the maser-dewar unit, filled with 6 liters of helium for 24 hours of operation is less than 40 pounds. The design of the dewar enables the cryogenic system to work over a wide range of vertical angles, thus facilitating the use of the maser at the feed of a large steerable antenna.     

Traveling wave tubes for communication satellites

Traveling wave tubes (TWT's) have contributed markedly to the development of communications satellites. As the prime-power consuming and transmitting device, the major transponder gain element, and the largest contributor to transmission nonlinearities, the TWT has been the focal point for continuous but carefully measured evolutionary improvements. Efficiency improvements continue to be made without compromising desired communications characteristics or tube lifetimes. These improvements have been made primarily in the RF circuit through loss reduction and phase-velocity tapering techniques, and in the spent-beam region through better multielement collector designs. Traveling wave tubes developed for satellites at 4 and 12 GHz are used as examples. Since TWT's ate life-limited devices, emphasis has been placed on techniques ensuring long life in satellite applications. Both oxide- and dispenser-type cathodes are discussed and data on life characteristics are presented. During the past decade, while generally demonstrating excellent space lifetimes, operating TWT's continue to approach their potential cathode wear-out life, which is theoretically of the order of 10⁵h.     

Extending the bandwidth performance of heterojunction bipolartransistor-based distributed amplifiers

An InAlAs-InGaAs-InP HBT CPW distributed amplifier (DA) with a 2-30 GHz 1-dB bandwidth has been demonstrated which benchmarks the widest bandwidth reported for an HBT DA. The DA combines a 100 GHz fmax and 60 GHz fT HBT technology with a cascode coplanar waveguide DA topology to achieve this record bandwidth. The cascode gain cell offers 5-7 dB more available gain (MAG) than a common-emitter, and is used to extend the amplifier's upper frequency performance. A coplanar waveguide design environment is used to simplify the modeling and fabrication, as well as to reduce the size of the amplifier. Novel active load terminations for extending the DA's lower frequency response were separately demonstrated. The active loads are capable of extending the lower bandwidth performance by two decades resulting in performance below 45 MHz. This work explores both design techniques and technology capability which can be applied to other distributively matched HBT circuits such as active baluns for mixers, active combiners/dividers, and low DC power-broadband amplifiers     

Recent dark-trace tube developments

Dark-trace tubes or skiatrons have certain advantages over bright display tubes which make their use desirable for information displays. These advantages are the ability to integrate visually, to store information, and daylight and sunlight viewing. Since World War II, at the time the 4AP10 was used, several of the basic disadvantages have been corrected in part, such as erase time, writing speed, contrast and color. Several experimental tube types have been evolved and others are under development. Some radical improvements in one or more of the limiting characteristics have been achieved. These were accomplished in several ways, including low heat capacity screens, conductive film techniques, different screen compositions, special electron optics, and other techniques. The characteristics and limitations are summarized for different tube types together with several suggestions for possible further research and development in the field. The equipment design factors peculiar to these tubes, such as stringent voltage requirements, sweep failure protection, beam current limiting circuitry, and other items are discussed to aid preliminary equipment designers in the use of these tubes.     

一种提高放大器增益和带宽的设计技术分析

运算放大器是信号处理中的基础模块,是高性能混合信号数据转换器、片上系统(SoC)等的重要组成部分。低功耗和高性能的基础电路模块成为系统发展的瓶颈,因此对增益和带宽增强型运算放大器的研究成为业界关注的焦点。为了研究运算放大器增益和带宽优化设计技术,实现低功耗高性能的解决方案,对电流重用技术的产生背景和技术演进作了较为详细的分析,体现了在技术进步过程中对结构的优化和改进,对高性能系统集成设计具有重要的参考意义。     

Harmonic generation in octave bandwidth traveling-wave tubes

This paper describes the investigation of harmonic generation in traveling-wave tubes (TWT's) via large-signal analysis and digital computer techniques. Efficiency degradation and harmonic power content are shown to be importantly related to such TWT design considerations as circuit dispersion, harmonic coupling impedance ratio, and gain level. Also described is the phenomenon of second harmonic interference in the beam bunching process and how it leads to substantial efficiency reduction in TWT's employing relatively nondispersive structures.     

Design and performance of wideband GaAs MMIC's for high-speedoptical communication systems

Advanced design techniques for GaAs wideband direct-coupled amplifiers are described. The amplifier achieved a 20 dB gain with a 3 dB bandwidth of 13 GHz and a 5-7 dB noise figure. An equalizing amplifier module consisting of amplifier and variable attenuator monolithic microwave integrated circuits (MMICs) exhibited a high gain of 43 dB over a 10 GHz band with a controllable gain of 20-43 dB     

A proposal of broad-bandwidth vertical-cavity laser amplifier

We propose a generic vertical-cavity amplifier (VCA) using a coupled-cavity design to broaden the bandwidth. Calculations are made for cavities with GaAs-AlAs and GaAs-Al_xO₂ distributed Bragg reflectors (DBR). We found that at reasonable pumping levels the VCA increased the bandwidth by 85% (GaAs-AlAs) to 500% (GaAs-Al_xO₂) as compared to a simple two-mirror structure similar to vertical-cavity surface-emitting lasers. In particular, the GaAs-AlAs VCA shows a bandwidth of 2 nm at 6-dB signal gain, while the GaAs-Al_xO₂ VCA demonstrates a 5-nm bandwidth at 6-dB signal gain with no ripple at required single-pass power gain of ~2-2.5%. Furthermore, as large as 30-nm bandwidth in a lossless bandpass filter can be obtained     

Digitally-controlled automatic gain control circuits for CMOS CCDcamera interface

Automatic gain control circuit (AGC) design techniques for CMOS CCD camera interface systems are described. The required gain of the proposed AGC is controlled directly by digital bits. The amplifying function of the AGC is divided into three stages for high-speed operation. A capacitor-segment combination technique considerably improves the effective bandwidth of the AGC. While the three-stage prototype shows 32 dB AGC dynamic range in 1/8 dB steps, the proposed two-stage AGC reduces the power and chip area further     

Optimum Design for RF Windows in Millimeter Wave High Power Tubes

The pill-box and block RF windows for millimeter wave (MMW) tubes are presented. The pill-box window is suitable for broadband MMW tubes. And the block window can be used for high power tubes in short MMW. The equivalent circuits for two windows are given. To reach better match characteristics in wider operating bandwidth, the optimum design methods for pill-box and block window in MMW tubes are described in this paper. The testing results show that the theoretic computation is fast and useful accuracy. The design methods possess references value to designer for MMW tubes.     

Proximity-coupled stacked circular-disc microstrip antenna withslots

The design and measured results of a proximity-fed stacked circular-disc antenna are described. The antenna has an impedance bandwidth of 26%, centred around 4.2 GHz, a gain of 8 dBi, and -30 dB cross-polarisation. An essential feature of the design is the presence of four linear slots in the bottom patch of the stacked arrangement     

High gain traveling-wave amplifiers

Modern techniques make it possible to build traveling-wave amplifiers with stable gains as high as 60 or 70 db. Such tubes can have relatively flat frequency response, and high gain over frequency ranges well in excess of two to one. In design it is necessary to pay strict attention to adequate isolation of the input and output so that spurious feedback paths do not cause oscillation or excessive variation of gain with frequency. In many practical applications, such tubes are required to operate with source and load impedances which produce large reflections of energy. Special design techniques result in tubes which are stable under such conditions. Another feature which can be achieved in modern tubes is a high ratio of backward loss to forward gain, so that the amplifier can very effectively isolate an oscillator. The recent design trend is toward higher currents and lower voltages, which is of direct benefit to the equipment designer, since it results in shorter tubes as well as simpler power supply designs, With the use of highly convergent electron beams, cathode current density can be kept quite low, and ion bombardment effects minimized, so that excellent life is achieved. Traveling-wave amplifiers may be readily phase modulated since small variations in the beam voltage yield large phase excursions. This characteristic is used for high level mixing. By proper gun design, it is possible to obtain good mixer action with modulation frequencies as high as a few hundred megacycles. The problems involved in obtaining the above characteristics and typical experimental results are illustrated by data on the STS-69, a half-watt twt for the 2 to 4 kmc frequency range.