Showing papers on "IMPATT diode published in 1997"

Optoelectronic microwave oscillators using diode lasers

Abstract: We will present the latest experimental results obtained with this 1.3 /spl mu/m oscillator that uses a diode laser optoelectronic oscillator; in addition to low frequency measurements of the phase noise of the 850 nm system. A configuration using two fiber loops used to further suppress the side modes will also be described.

Computer studies of quasi Read gallium arsenide IMPATT diode : including the effect of space charge

Abstract: Computer studies have been carried out on the effects of variation of impurity hump parameters of quasi Read high–low (hi–lo) and low–high–low (lo-hi–lo) gallum arsenide IMPATT diodes on their DC and microwave properties. The effect of mobile space charge has been included in the computer analysis. It turns out that the DC properties of the diode are sensitive functions of the width and doping concentration of impurity bumps. The optimum efficiency is found to be respectively 24.5% and 27.9% for hi–lo and lo-hi–lo diodes designed for 18 GHz frequency. The small signal admittance calculations show that a lo-hi–lo structure provides higher negative conductance and better quality factor compared with a hi–lo structure of GaAs Impatt diode.

Effect of Punch through on the mm Wave Properties of Si SDR n+np+ IMPATT Diode in the 94 GHz Window

Abstract: The effect of punch through on the small signal properties of single drift n + np + silicon IMPATT diode near 94 GHz atmospheric propagation window has been studied. The computed results show that for a fixed bias current density, when the space charge effect is not prominent, the optimum negative conductance decreases, and the corresponding frequency for highest negative conductance increases with the increase of punch through determined by doping density and the thickness of the active layer. The increase of punch through produces an upward shift in the operating frequency of the device. It is shown that an increase of punch through leads to a decrease in the conversion efficiency, and the negative conductance of the device.

Experimental studies on a modified resonant-cap microwave IMPATT amplifier with improved performance

Abstract: Experimental studies have been carried out on a modified resonant-cap IMPATT amplifier operating in the X-band (8.0-12.0 GHz) to investigate the improvement of its performance over the normal resonant-cap amplifiers. The modified resonant-caps have been designed by incorporating appropriately sized circumferential slots on the disc of the resonant-cap and optimizing the cap height suitable for amplifier operation. A double-peaked gain-frequency characteristic has been observed which leads to a threefold improvement of the bandwidth of the optimized modified cap amplifier compared with the optimized normal (i.e. unslotted) circular cap amplifier for the same gain. The height optimized modified cap amplifier also shows a significant improvement of the linearity and the r.f. power added to the output of the amplifier. The results of this novel design to improve the bandwidth and linearity of a cap-type IMPATT amplifier in the X-band can also be applied in the millimetre-wave frequency range.

Nonlinearity compensation of laser diode and other semiconductor diodes

Abstract: A high-linearity light source comprising a first semiconductor diode (eg, a light-source diode such as a laser diode or a light-emitting diode, or a light-receiving diode such as a photodetector) and a nonlinearity compensation network with a second, compensation, semiconductor diode is provided The first and second diodes are connected in an antiparallel configuration with either an AC signal source (for light emission) or a load (for light receiving) and in separated DC bias paths By varying the relative biasing of the diodes (eg, using a variable resistor in series with a diode), the capacitance of the combination of diodes cancels, and the linearity of the system improves With a properly biased compensation diode the even-order nonlinearity distortion can be cancelled completely

FM Noise and Synchronization Behavior of a SIMMWIC 76.5 GHz Front-End

Abstract: SIMMWIC’s (Silicon Monolithic Millimeter Wave Integrated Circuit) have gained increasing interest as receivers and transmitters in the millimeter wave region. They provide new solutions for near-range sensor and communication applications in the frequency range above 50 GHz. Particular advantages are the capability of very easy monolithic integration of a complete radiating oscillator, a high degree of technological reproducibility, small size and, thus, low cost1. A typical millimeter wave front-end consists of an IMPATT diode integrated in a planar resonator. This resonator acts simultaneously as an antenna resulting in an active antenna configuration. Due to the low q-factor of the resonator, for some applications, like FM-CW-radar, the frequency stability and the phase noise behavior of the front-end are insufficient. Using a phase-locked-loop is a practicable way to stabilize the oscillation frequency and suppress the phase noise. However, many millimeter wave components such as frequency dividers, voltage controlled oscillators (VCO’s) and phase/frequency comparators are required resulting in an expensive and complex multichip system.

Space charge induced variation in silicon double drift IMPATT diode parameters

Abstract: The effect of space charge on the space charge region (SCR) width, diode voltage and the maximum field in Si double drift IMPATT diode is studied under the operating conditions for various current and doping densities. The rate of increase in SCR width and diode voltage with current density depends appreciably on majority carriers' space charge. The simple analytical expression for the variation of these parameters with current density is presented. The author's analytical expression for the variation of SCR width and diode voltage with current density is found to be the best fit throughout the range, while Kuno's approximate estimation (1979) for the increase of SCR width is valid only at low current densities where the carriers' space charge is insignificant. The analytical expression and the data are thus useful for the design of practical IMPATT diodes at microwave and millimetre wave frequencies.

Large Signal Model of an Optically Controlled GaAs IMPATT Diode

Abstract: A large signal model of an optically controlled Read-type GaAs IMP ATT diode has been presented. In contrast to other existing theories, we consider the effect of photogenerated carriers in the avalanche zone which significantly affects the device characteristics in the illuminated condition. The model presented here is used to examine the effect of illumination on the output power, efficiency and negative conductance of the device. It has been found that for constant bias current, the output power and efficiency of the device are strong functions of the incident optical power. The model can be used as a basic tool for optimising GaAs IMPATT diodes for optically controlled applications in microwave region.

Computer Studies on Pulsed Silicon MM-Wave IMPATT Diodes for various DDR Structures at High Current Density

Abstract: A review of the pulsed mode high power generation in silicon DDR IMPATT devices at high current density has been presented together with the current work of the authors in the same subject.Computer studies have been presented on silicon pulsed IMPATT diodes with various double drift region (DDR) structures for operation at 94 GHz at a current density of 100 KA/cm2. Three structures: (i) flat, (ii) SLHL, i.e., low-high-low structure with single bump on either side of the p-n junction and (iii) DLHL, i.e., low-high-low structures with double bumps on either side of the p-n junction have been investigated. The dc & small-signal results indicate that suitably designed silicon DDR IMPATT devices with double impurity bumps on either side of the junction exhibit much higher negative conductance and power output than other structures.It is seen that appropriately designed DDR structures could be operated at a high current density of 100 KA/cm2, with narrow avalanche zone to give sufficient W-band pulsed power, wh...

Design, development and characterisation of microstrip IMPATT oscillator

Abstract: Solid state microwave oscillators are becoming increasingly important in microwaves, millimeter-waves and submillimeter wave frequency ranges. Previously, traditional waveguide based oscillators using IMPATTs have been popular. The paper deals with the design, development and characterization of a microstrip IMPATT oscillator in the Ku-band. Since IMPATTs large signal behaviour usually is not well understood and the circuits are electromagnetically complex, it is difficult to characterize accurately the circuit performance in a microstrip configuration. Therefore, a simple circuit topology is adopted using a GaAs IMPATT diode with an operating frequency range of 14-17 GHz and a design center frequency at 14 GHz. The entire design is realized on a polytetrafluroethylene-5880 substrate with a dielectric constant of 2.2. All line lengths and widths are calculated using EESOF's Microwave software packages-LINECALC and TOUCHSTONE. The results show an output power of 190 mW at 12.7 GHz, with a slight modification, an oscillator frequency of 13.88 GHz is achieved. Conclusions and future scope of work are also discussed. The design presented is first step towards the development of a microstrip IMPATT oscillator. Experimental work is on for further improvements in performance.

Experimental studies on the dependence of tuning properties on the diameter of the post below the cap and the cap thickness of X-band resonant cap Impatt oscillators

Abstract: An experimental investigation is made on the tuning of resonant cap Impatt oscillators at the X-band. This includes the dependence of the oscillation frequency and the microwave power output on the diameter of the post below the resonant cap and the cap thickness. From the study of the tuning properties, the optimum dimensions of the resonant cap cavity and the geometrical parameters for having maximum power output for a given Impatt diode can be obtained. The results would be useful in the design of resonant cap Impatt oscillators.