Wideband microwave amplifier with two antiparallel high-efficiency-diode pairs

A K-shaped antiparallel microstrip amplifier having four high-efficiency avalanche diodes has provided 400 W at 1.01 GHz with 8.8 dB power gain and 1.23% bandwidth. A novel fishbone-shaped tuning plate has worked not only to widen the bandwidth to 10%, but also, together with stagger-tuned antiparallel pairs, to increase the gain bandwidth from 94.8 MHz to 447 MHz.     

Varactor-tuned integrated Gunn oscillators

Electronic tuning of Gunn diodes in hybrid integrated circuits has been studied. Microstrip transmission lines were used to form resonant circuits into which a Gunn diode and a varactor diode were mounted to provide the microwave power and frequency tuning, respectively. Basically, two types of circuits have been investigated. The first is a half-wavelength open-circuited microstrip `cavity' with this transmission line and the varactor diode attached between the end of the cavity and an RF ground. The second is a lumped LC circuit in which the inductance of a short high-impedance microstrip line is resonated with the lumped capacitance of the varactor diode. The latter circuit provides a tuning range of over 10 percent at 7.5 GHz. The power output varies within 2 dB in the tuning range.     

High Power, p-i-n Diode Controlled, Microwave Transmission Phase Shifters

An iterative circuit, diode, transmission phase shifter is discussed, having a canonic form that consists, of a length of transmission line symmetrically loaded at its ends by small susceptances whose values are diode controllable. The spacing of the susceptances is chosen so that their reflections are nearly mutually canceling, (about a quarter wavelength if equal magnitude, opposite sign susceptances are used). A change of electrical length of the section of 23/spl deg/, in principle, is obtainable with a maximum input VSWR of 1.04. Eight section, experimental circuits yielded 180/spl deg/ total phase shift with less than one decibel of loss in the L and S bands and peak RF power capability to 15 kilowatts. Operation to 140 kilowatts peak power was achieved with reduced phase shift per section. The transmission phase shifter is believed to be well suited as a phase control element for beam steering of array antennas.     

Anti-parallel pair of high-efficiency avalanche diodes

Phase-locking of two high-efficiency avalanche diodes has been achieved by placing the diodes on a transmission line in anti-parallel direction with each other at a separation of (λ/2-vτd). The maximum pulsed RF power obtained from the anti-parallel pair was 367 W at 1.02 GHz.     

Computer simulation of LSA oscillators with high doping to frequency ratios

Computer simulations of twice oversized n-GaAs diodes with random doping fluctuations operated in a transmission line (multiresonant) circuit are presented. LSA operation in this multiresonant circuit, which provides an RF square wave voltage across the diode, has been obtained for n/f ratios as high as 1 × 10⁶s/cm³.     

Large-Signal Silicon and Germanium Avalanche-Diode Characteristics

A technique for measurement of the large-signal single-frequency microwave amplifier admittance of avalanche diodes is described, and results are presented for silicon and germanium avalanche diodes. Single-frequency amplifier operation can provide a unique characterization of diode-admittance variation with RF drive for diodes operated near the optimum transit angle (the case in which all harmonic voltages are negligibly small compared to the fundamental). Such characterization is useful for predicting diode performance for circuits in which the harmonic voltages are not large enough to have an appreciable effect on the diode admittance at the fundamental frequency. A process of matching quadratic forms to the above admittance data which may be used for calculation of diode terminal admittance and power output is discussed. The usefulness of the measurement technique is illustrated by the agreement of the calculated maximum power output with the measured power output in a single-transformer coaxial circuit. The corresponding circuit admittance may be used for circuit-design purposes and for evaluating variations in diode-assembly techniques. The ability to obtain the diode equivalent circuit as a function of incident power allows studies in the design of the associated semiconductor device. For example, one has the capability of obtaining an accurate single-frequency large-signal model near the optimum transit angle, a model which can be studied without building a circuit. With this model it is possible to carry out optimization procedures at considerable savings of time and money.     

Circuits for High-Efficiency Avalanche-Diode Oscillators

This paper describes and analyzes the circuits which have been used successfully for TRAPATT oscillator studies. The results lead to a better understanding of the TRAPATT oscillator and yield a simple model of the oscillator which is useful for circuit design. The circuit characteristics of an experimental TRAPATT oscillator are determined from measurements on the circuits and from equivalent circuit model calculations. The following conclusions can be drawn from the analysis. First, the avalanche diode requires sufficient capacitance near the diode to sustain the high-current state required for TRAPATT operation. Secondly, at a distance from the diode corresponding to approximately one half-wavelength at the TRAPATT frequency the transmission line containing the diode should be terminated by a low-pass filter. The function of the filter is to pass the TRAPATT frequency and to provide a shorting plane for the harmonics of that frequency. Finally, on the load side of the filter, tuning for the TRAPATT frequency is required. The model of the circuit described above suggests a simple explanation of the diode-circuit interaction in a TRAPATT oscillator. Simplified waveforms suggested by the model have been used to calculate power out-put, efficiency, dc voltage change, and RF impedance for the oscillator. The results agree within a few percent with those obtained for an experimental oscillator. An important conclusion of the analysis is that the high-efficiency operation of avalanche diodes at frequencies in the UHF range can be explained by the TRAPATT theory, even though the trapped-plasma or low-voltage state may last only 1/20th of the oscillation period.     

The effect of injecting contacts on avalanche diode performance

Metal-semiconductor contact injection on the junction side of diffused-mesa avalanche diodes has been found to have a significant effect on the performance of these diodes as oscillators. A minority carrier injection ratio of 6 percent reduces the efficiency of what would be 9 percent efficient diodes to less than 1 percent and increases the FM noise by a factor of 2 as tested in a 6-GHz oscillator circuit. The dependence of the minority carrier injection ratio of the metal-semiconductor barrier upon current density has been measured and quantitatively modeled. Calculated values of diode admittance, including the effects of injection at the contact, are shown to be in agreement with measured values of both small-signal diode admittance versus frequency and large-signal diode admittance versus RF voltage. Germanium avalanche diodes with low-minority carrier injection contacts have demonstrated CW oscillation efficiencies greater than 9 percent at 6 GHz. The realization of low-injection contacts is shown to be a requirement for achievement of high-efficiency avalanche oscillation.     

A Novel Circuit Architecture for High Performance of High-order Subharmonic Mixers

A novel circuit architecture for high performance of high-order subharmonic (SH) mixers is proposed in this paper. According to the specified harmonic mixing order, one or more mixer diodes sub-arrays and corresponding power divider as well as phase shift network for RF and LO signals are arranged in the circuit. This proposed SH mixer circuit has improved conversion loss, wide dynamic range and high port isolation for high-order SH mixers. By phase cancellation of idle frequencies, the proposed SH mixer circuit can eliminate complicated design procedure of idle frequency circuits; by phase cancellation of leakage LO power to RF and IF port, and leakage RF power to LO port, the mixer circuit can get high port isolation in LO-IF/RF and RF-LO. The increased antiparallel diode pairs in each sub-array will also lead to well performance by lowering effective series resistance. The proposed SH mixer circuit can be easily realized with power divider and phase shift network for RF and LO signals.     

TRAPATT oscillations in a p-i-n avalanche diode

The characteristics of TRAPATT oscillations in a p-in diode are discussed and an approximate semi-analytical solution for the diode voltage waveform is derived when the diode current is a square wave. It is shown that a traveling avalanche zone is not necessary to generate a dense "trapped" plasma and that the boundary conditions prevent the trapped plasma from completely filling the depletion layer. Typical voltage waveforms and corresponding diode power, efficiency, and impedance at the fundamental and higher harmonics are presented. When the diode current is a square wave the diode does not necessarily exhibit a negative resistance at all higher harmonics. A computer program for TRAPATT oscillations in a p-i-n diode is described. Its running time is two or three orders of magnitude less than more exact time domain computer analyses. Typical results of diode power, dc to RF conversion efficiency, and required circuit impedances are presented for several different current waveforms which are composed of up to the seventh harmonic of a square wave and the first two harmonics of a half-wave sine wave. It is shown that high-efficiency oscillations are possible with diode currents composed of only the fundamental and one harmonic.     

110GHz 阻性平衡三倍频器设计

本文介绍了一种基于阻性肖特基二极管芯片UMS DBES105a 的110GHz 三倍频器,通过两个芯片反向并联形成 了平衡结构,同时提高了倍频器的功率承受能力。电路设计中使用二极管三维电磁模型,匹配设计时未设计专门的输入 过渡和滤波器,而是直接经行匹配设计,提供了更多的可优化参量,以达到最佳的匹配效果和带宽。经过HFSS 和ADS 联合仿真,在频率为31~44GHz,功率为20dBm 的驱动信号激励下,三倍频器输出频率大于7dBm,最大输出功率为 9.1dBm@105GHz。     

Modeling high-speed optical transmission systems

Computer simulation of a 2.5-Gb/s intensity-modulated/direct-detected optical system with high path dispersion is described. This simulation, based on single-mode laser diode rate equations, includes transmit and receiver circuit filtering, receiver circuit noise, avalanche photodiode noise, fiber dispersion, and laser chirp. The rate equations are sufficiently general to model mode-offset distributed feedback laser diodes. The system power penalty, due to laser chirp and fiber dispersion, is calculated using Gaussian quadrature numerical integration. By simulating a population of some 12800 laser diodes and correlating the performance of each laser in a transmission system with its spectral characteristics, it is possible to deduce laser specifications that will assure satisfactory operation in long-span links. These results are used to study a laser diode specification under consideration by CCITT, and, by studying the simulated laser line shapes, some modifications to the CCITT specification are considered     

Ultrahigh-Speed Diode Switch for 50 GHz Band Utilizing Avalanche Breakdown in Varactor Diodes

Ultrahigh-speed switches for the 50 GHz frequency range utilizing avalanche breakdown in varactor diodes have been developed as transmitter-modulators for millimeter-wave PCM communication systems. By switching the diode between forward conduction and avalanche breakdown, better performance was obtained than with standard switching conditions. A typical switch of transmission type with a silver-bonded Ge varactor, GSB3C for an input power of +17 dBm at 48 GHz, gave an insertion loss of 3.5 dB with a maximum attenuation of 31 dB. Some of the distinctive characteristics of diode switches utilizing avalanche break-down in varactor diodes are discussed.     

Class D current-driven rectifiers for resonant DC/DC converterapplications

Analyses and experimental results are given for a family of three Class D current-driven rectifiers. The diode current is half-sine wave and the diode voltage is a square wave. The diode forward voltage and forward resistance are taken into account in the analyses. The basic performance parameters of the rectifiers are determined, such as input resistance, voltage transfer function, efficiency, and power factor. The ripple voltage is estimated, and some effects of the equivalent series resistance and equivalent series inductance of filter capacitors on the ripples are discussed. The experimental results were obtained using IR31DQ06 Schottky diodes at 1 MHz and 16 W output power     

Large-Signal Equivalent Circuits of Avalanche Transit-Time Devices

A large-signal analysis for IMPATT diodes is derived, which allows carrier multiplication by impact ionization to occur at every point in the diode. Therefore, the operating characteristics of IMPATT diodes with a wide range of realistic doping profiles can be investigated. For a given operating frequency, RF voltage, dc bias current, and doping profile, the admittance, power output, efficiency, bias voltage of a diode can be obtained. An equivalent circuit the diode package, microwave circuit mount and diode, is obtained experimentally. Using this circuit, the admittance of the diode is measured by a reflection-type circuit and an oscillator circuit as a function of the RF voltage, dc bias current, and frequency.     

1 kW microstripline TRAPATT oscillator

A microstripline-oscillator circuit capable of operation with one or several stacked TRAPATT diodes is described. Peak power of 1 kW at 1 GHz has been achieved from four diodes operated in series. Experiments have shown the importance of a short-circuited resonant transmission line and a high pulser output impedance for efficient, stable operation of the TRAPATT diode stack.     

Study and implementation of a low conduction loss zero-current resonant switch

Zero-current (ZC) resonant switches allow one to reduce the switching losses in high-frequency DC/DC switched mode power supplies. ZC resonant switches can be either unidirectional (half-wave) or bidirectional (full-wave). If a conventional power MOSFET is chosen to implement the ZC resonant switch, the turn-on of the slow intrinsic diode has to be avoided. This is usually done with a fast blocking diode, which is connected in series with the MOSFET. Furthermore, an antiparallel fast diode is added when a FW ZC resonant switch is required. The conduction losses are relevant in this implementation, owing to the threshold voltage and to the series resistances of the two diodes. In this paper, a low-conduction-loss FW ZC resonant switch has been proposed. Its implementation is based on a power MOSFET and a single antiparallel Schottky diode. The possibility of an implementation with a power MOSFET alone is also discussed. A control circuit suitable for the proposed ZC resonant switch has been described. The experimental results obtained from a ZCS-QR buck converter are discussed.<>     

Microstrip High-Power High-Efficiency Avalanche-Diode Oscillator

A simple microstrip oscillator circuit has been designed and operated satisfactorily with high-power high-efficiency avalanche diodes. The power output obtained from a single diode chip is ahout 100 watts at 1 GHz with efficiencies of 25 to 30 percent. Mechanical tuning capability of a few hundred megahertz and a combined power output from series-connected diodes have been demonstrated using the circuit. An essential part of the circuit is a low-pass filter tuning section which enables the circuit to support high-order harmonics including the transit-time frequency and prevents them from getting to the load. Probe measurements of the electric field show strong second as well as third harmonics inside the circuit.     

Harmonic extraction from high-efficiency avalanche diodes

A novel harmonic-extraction method for operation of high-efficiency avalanche diodes has been demonstrated. It has been shown that high-efficiency power output can be obtained not only at the trapped-plasma frequency, but also at harmonic frequencies with respect to the trapped-plasma frequency. Second-harmonic powers of 110 W at 2.67 GHz with 22-percent efficiency from L-band diodes, and 64 W at 4.85 GHz with 15-percent efficiency from S-band diodes have been obtained. Third-harmonic extraction has extended the power output into the lower X-band frequency. Microstrip circuits for harmonic-extraction have been developed and analyzed. The circuit impedance requirements at the diode terminals have been computed. The circuit has been discussed in terms of a multiple-reflection triggering process. Useful information for circuit design has been deduced from a series of harmonic-extraction experiments. The voltage waveforms have been measured and have shown evidence of harmonic extraction and its association with the trapped plasma mode.