1.9 GHz low loss varactor diode pre-distorter

Pre-distorters implemented at circuit level using series diodes have a high loss. The method presented here combines source/load second harmonic control with a parallel connected varactor diode. A reduction of 15 dB in the spectral regrowth at 1.9 GHz is achieved with a low loss of 2 dB due to the varactor diode     

Low noise GaAs varactor and mixer diodes prepared by molecular beam epitaxy

Schottky-barrier varactor and mixer diodes have been made from Ge-doped GaAs layers grown by molecular beam epitaxy. A microstrip parametric amplifier circuit incorporating a hyperabrupt varactor diode has given a noise temperature of 120 K and bandwidth of 180 MHz at 15 dB gain when pumped at 34 GHz, and a mixer diode mounted in a cryogenic receiver circuit had an s.s.b. noise temperature of 180 K at 90 GHz.     

Avalanche breakdown characteristics of a diffused P-N junction

A one-dimensional analysis is presented on the avalanche breakdown characteristics of a diffused p-n junction diode. By numerically integrating the carrier ionization rate in a junction space-charge layer, avalanche breakdown voltage is calculated for diffused diodes of silicon and germanium; this voltage is graphically illustrated throughout a range of parameters applicable to most practical situations. In addition, for calculating the maximum cutoff frequency of varactor diodes, junction capacity is similarly illustrated assuming the device is biased to avalanche breakdown. From these illustrations, and from an accompanying nomograph which relates the physical constants of a junction to its impurity atom gradient, the above parameters can be readily established without additional calculations. Further, examples are also presented to demonstrate the reduction of breakdown voltage resulting from a rapid increase of conductivity within the space-charge layer of a diffused p-n junction; this situation approximates many epitaxial and double diffused structures.     

A 50-GHz silicon IMPATT diode oscillator and amplifier

Recent experimental observations on a silicon impact avalanche transit-time diode oscillator and amplifier CW-operated at 50 GHz are presented. 1) CW oscillation power of 100 mW was obtained at an overall efficiency of 2 percent. The oscillation frequency was continuously tunable over a 1.3-GHz range by a sliding short. 2) Phase-locking has been achieved with a maximum normalized gain-bandwidth product of 0.1. The minimum locking signal power required for a 500-MHz locking bandwidth was 20 dB below the oscillator output. 3) Electronic tuning of the oscillator frequency was demonstrated by placing a millimeter-wave varactor diode in the tuning circuit. The output frequency versus the bias voltage on the varactor diode was linear with maximum frequency deviation of 300 MHz. Frequency modulation of the oscillator by driving the varactor with a sinusoidal source was obtained at a modulation frequency of 50 MHz. 4) Stable amplification with 13-dB gain was obtained, centered at 52.885 GHz with a 3-dB bandwidth of 1 GHz. The maximum output power obtained was 16 mW. Higher gain of about 17 dB was obtained at a reduced bandwidth. The noise figure of the amplifier was 36 dB. Equivalent circuits for the oscillator and the amplifier are derived. The calculated results agree reasonably well with the experimental observations.     

Macro-micro frequency tuning antenna for reconfigurable wireless communication systems

A small-sized (radiator sime10times8 mm) microstrip monopole antenna for reconfigurable macro-micro frequency tuning is presented. The proposed antenna operates in WiBro (2.3-2.4 GHz) and WLAN 802.11a/b (2.4-2.48 GHz/5.15-5.35 GHz) service bands with a constant antenna gain. Two frequency tuning diodes, a pin diode and a varactor, are incorporated into a meander type radiator. The pin diode is used for frequency switching (macro-tuning) between 2 GHz band and 5 GHz band. In addition, the varactor is used for frequency tuning (micro-tuning) within wireless service bands (2.3-2.48 GHz and 5.15-5.35 GHz) to produce constant antenna gain     

Frequency Multiplication By A P-I-N Diode When Driven Into Avalanche Breakdown

An investigation of frequency multiplication using a step-recovery diode (SRD) driven into avalanche breakdown is presented. This mode of operation, which is called the "breakdown mode," consists of a reverse-biased p-n junction, SRD, or IMPATT diode driven into reverse breakdown by an ac signal source. As the diode voltage passes from reverse bias to reverse breakdown and avalanche, the state of the diode switches quickfy from a depletion-layer capacitance to an avalanche inductance; hence the production of strong harmonics. A theoretical analysis and experimental investigation of a coaxial/waveguide 2-6-GHz frequency multiplier using HP5082-0320 step-recovery diodes, [R/sub s/ = 0.75 Omega, C/sub d/(-6/sub v/) = 1.0 pF] shows that the breakdown-mode frequency multiplier has a higher conversion efficiency than the conventional "charge-storage" multipuer. A measured conversion efficiency of 73 percent was achieved while the same circuit configuration produced 52 percent for the same diode used as a charge-storage multiplier under optimum forward-drive and tuning conditions. Also the theory developed in this paper indicates a maximum possible conversion efficiency of 80 percent for the breakdown-mode multiplier, which corresponds closely with the measured results, and a maximum theoretical efficiency for a forward driven diode of 64 percent. The performance of an FM microwave system was monitored using the breakdown multiplier as a LO in which a baseband SNR of 59 dB was recorded.     

Millimeter-wave diode-grid frequency doubler

Monolithic diode grid were fabricated on 2-cm² gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter-wave frequency multiplier array concept. An equivalent circuit model based on a transmission-line analysis of plane wave illumination was applied to predict the array performance. The doubler experiments were performed under far-field illumination conditions. A second-harmonic conversion efficiency of 9.5% and output powers of 0.5 W were achieved at 66 GHz when the diode grid was pumped with a pulsed source at 33 GHz. This grid had 760 Schottky-barrier varactor diodes. The average series resistance was 27 Ω, the minimum capacitance was 18 fF at a reverse breakdown voltage of -3 V. The measurements indicate that the diode grid is a feasible device for generating watt-level powers at millimeter frequencies and that substantial improvement is possible by improving the diode breakdown voltage     

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.     

Millimeter-wave diode-grid phase shifters

Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers with 1600 Schottky-barrier varactor diodes. Shorted diodes are detected with a liquid-crystal technique, and the bad diodes are removed with an ultrasonic probe. A small-aperture reflectometer that uses wavefront division interference was developed to measure the reflection coefficient of the grids. A Phase shift of 70° with a 7-dB loss was obtained at 93 GHz when the bias on the diode grid was changed from -3 V to 1 V. A simple transmission-line grid model, together with the measured low-frequency parameters for the diodes, was shown to predict the measured performance over the entire capacitive bias range of the diodes, as well as over the complete reactive tuning range provided by a reflector behind the grid, and over a wide range of frequencies form 33 GHz to 141 GHz. This shows that the transmission-line model and the measured low-frequency diode parameters can be used to design an electronic beam-steering array and to predict its performance. An electronic beam-steering array made of a pair of grids using state-of-the-art diodes with 5-Ω series resistances would have a loss of 1.4 dB at 90 GHz     

Large-area varactor diode for electrically tunable, high-power UHF bandpass filter

An electronically tunable, high-power, UHF (225-400-MHz) bandpass filter which utilizes large-area, high-capacitance varactor diodes has been designed and tested. The varactor diodes with 100-V breakdown potential, uniform impurity density in the active layer and 400-pF capacitance at -8-V bias are used as the tuning elements of the filter. The diodes are fabricated from epitaxial layers grown on high-conductivity silicon substrates. The epitaxial layers include an n⁺transition layer between the substrate and n-type active layer to minimize the growth defects in the n layer which reduce the breakdown potential to a fraction of the theoretical value. Measurements in a test cavity at 151 MHz indicate a diode Q of 190 at -8-V bias. Input power levels of 1-5 W can be accommodated across the tuning range. Insertion loss varies from 4 to 7 dB and intermodulation products are suppressed 30 dB or more for two input tones of 1 W each. This filter exhibits an order-of-magnitude improvement in power-handling capability over present state-of-the-art filters.     

IMPATT operation below the avalanche frequency

Very high output powers are obtained with double drift IMPATT diodes at current densities which shift the avalanche frequency above the oscillation frequency: 30-40 W pulsed around 90 GHz. This operation mode cannot be explained in terms of the conventional READ theory. A numerical large signal simulation shows that avalanche multiplication over the whole diode takes place. At high current densities the double drift device behaves like a pin diode without the unfavourable breakdown of the ionisation process in the centre of the diode.<>     

Laser diode switch

Optical switches using laser diodes are proposed. Basic switching operation using an AlGaAs CSP laser is demonstrated for the first time. Isolation is better than 71 dB, signal bandwidth is broader than 1.5 GHz, and switching time is shorter than a few nanoseconds.     

高超噪比微波固态噪声源设计

固态噪声二极管的雪崩散弹噪声在一定条件下近似为白噪声。根据固态噪声二极管在雪崩击穿状态的等效电路,设计出与之匹配的电路结构,以实现超噪比的最大输出。在8.6~9.6 GH z,超噪比达到32~34 dB,平坦度±1 dB,超噪比随温度变化小于0.01 dB/°C。     

8～20GHz GaAs pin二极管单片单刀双掷开关

基于中国科学院微电子研究所的GaAs pin二极管工艺,设计、制作并测试了一种单片单刀双掷开关.在8～20GHz频段内,开关正向导通时的插人损耗最小值为1.5dB,输入和输出端的同波损耗大于10dB;开关关断状态的隔离度最大值为32dB.开关的支路采用串联-并联-并联的结构,其中的GaAs pin二极管基区厚为2.5μm.在1.3V的偏置电压下,正向导通的串联二极管工作电流为     

A comparison of silicon and gallium arsenide large signal IMPATT diode behaviour between 10 and 100 GHz

A large-signal computer simulation of an IMPATT diode has been used to investigate the differences between gallium arsenide and silicon IMPATT diodes. The variations of efficiency with frequency, current density, series resistance, amount of punch-through and reverse saturation currents are all investigated.With no ‘parasitic’ effects the silicon diode efficiency remains almost constant between 10 and 100 GHz, whereas the efficiency of gallium arsenide diodes is higher than that of silicon diodes at 10 GHz but decreases to the silicon diode efficiency at 100 GHz. A lower residual avalanche particle current in gallium arsenide diodes results in a higher susceptibility to reverse saturation currents. In silicon diodes the higher material resistivity affects the efficiency more than in gallium arsenide diodes, the removal of series resistance by having a punched-through diode does not necessarily increase the efficiency. The difference between experimental results quoted in the literature and the theoretical calculations are considered in terms of these effects. By considering the differences in ionization coefficients and velocities between the materials the lower efficiency of silicon diodes compared to gallium arsenide diodes is explained, also the lower breakdown voltage of gallium arsenide diodes compared to silicon diodes of the same frequency, and the ‘forward-bias’ effect found at high frequencies in gallium arsenide diodes.     

A high efficiency 46 to 92 GHz all microstrip frequency doubler

Using packaged GaAs varactor diodes, a high efficiency 46 to 92 GHz frequency doubler has been developed. Microstrip circuits have been used to match the input and output impedances presented by the diode. A conversion loss of 8 to 10 dB was measured. This doubler circuit is useful for W-band (75 to 110 GHz) integrated circuit receivers and transceivers. The use of microstrip circuit can drastically reduce the fabrication cost in addition to size and weight.     

Electronic frequency tuning of TRAPATT oscillators

Experimental results of a novel electronically tunable microstrip Trapatt oscillator employing varactor diodes arc presented. A tuning range of 20 MHz, limited by the low voltage breakdown of the varactor diodes and the number of tuning stages used, for an oscillator with a centre frequency of 1.6 GHz and an output power of 9 W, was observed and found to be in good agreement with theory.     

超突变结变容管的设计模型

通过建立一种超突变结变容二极管的杂质浓度分布模型,并基于求解一雏泊松方程、雪崩击穿条件方程和电阻计算公式,推导了该模型的C-V特性、VBR、Rs和Q值,设计了用于分析该模型的模拟软件,阐述了模拟软件的运行流程.基于该模型和模拟软件,采用外延-扩散的方法研制了一种硅超突变结变容二极管,采用C-V法测量了外延材料的杂质浓度分布,结果表明材料的浓度分布与模拟结果相符.研制的变容二极管的主要参数:击穿电压VBR为50～55 V;电容变化比(C_4v/C_8v为2.42～2.44;VR=-4 V,f=50 MHz时的品质因素Q为150～180,实测参数与模拟结果吻合得很好.设计模型和模拟软件得到了验证.     

Aperture-coupled antenna with switchable polarisation and frequency agility

The design of an aperture-coupled microstrip antenna with switchable polarisation and frequency agility is studied. Switching between two orthogonal linear polarisations (LPs) is realised by mounting two switching pin diodes on the antenna. To achieve multi-operating frequency (frequency agility) on one of the LPs, a voltage-controlled varactor diode is loaded between the top-loaded square patch and the ground plane. From the measured results, a good cross-polarisation level is observed when operated in both linear states at around 2 GHz.     

Reversible breakdown voltage collapse in silicon gate-controlled diodes

A reversible breakdown voltage collapse is recorded in the high voltage range of the junction breakdown voltage vs gate voltage characteristic of silicon gate-controlled diodes, which is explained in terms of a spatial switching of the avalanche breakdown within the device structure. The collapse gate voltage is oxide-thickness dependent and is accurately predictable as the avalanche breakdown voltage of the deeply depleted MOS capacitor within the gate-controlled diode structure.The minimum oxide thickness required for approaching the bulk-determined breakdown voltage in field-plated planar diodes and transistors is found to range from 0.01 to 5.00 μm for substrate impurity concentration from 10¹⁷ to 5 × 10¹⁴ cm^?3, according to a design plot provided in the paper.