Simultaneous compression and amplification of ultrashort pulses atMHz repetition rates

The authors report simultaneous compression and chirped pulse amplification at megahertz repetition rates of ultrashort pulses using a cavity-dumped dye laser with a pumping argon ion laser as the amplifier. In a single stage, the pulse is compressed by a factor of 25 and the energy per pulse is simultaneously increased by a factor of 2, without reducing the repetition rate. Starting with a pulse that has a duration of 4.3 ps and a peak power of 5.8 kW, a pulse with a duration of 170 fs and a peak power of 294 kW is obtained. A second stage of pulse compression is used to obtain a broadband pulse with a duration >~50 fs and a peak power of ~100 kW at 2 MHz     

Equivalent transformations for the mixed lumped Brune-type sectionand uniform transmission line

As an analytical method for nonuniform transmission lines (NTLs) equivalent transformations are extended to a more general case, namely a mixed lumped Brune-type section and a uniform transmission line (unit element, UE). Circuits consisting of a cascade connection of a lumped Brune section and a UE are equivalent to one consisting of a cascade connection of a nonuniform transmission line whose characteristic impedance distribution is expressed with a trigonometric function and a lumped Brune section. This equivalent transformation method is easily applied to a circuit consisting of a lumped C section and a UE. The equivalent circuit is a circuit consisting of an NTL and a lumped C section. In this case, the characteristic impedance distribution of the NTL may be expressed in terms of a hyperbolic function. Exact network functions of the NTLs are easily obtained from the equivalent circuits without solving the telegrapher's equation. By considering the limiting case of these equivalent transformations, equivalent transformations for circuits consisting of a cascade connection of a lumped resonance circuit and a circuit and a uniform transmission line are derived     

Detection of circular arcs for content-based retrieval from animage database

Methods are discussed for producing a summary of geometric content for images from a specific geological application, which can be used for content-based retrieval of interesting images from a large database. Using a data set of 100 images, it is shown that a local are detection scheme provides a more concise and hence a better summary of image content than a conventional edge map, while giving a superior performance     

The Matrix Formulation of Scattering Problems

Two regions in space are coupled through an opening in a perfectly conducting surface. By using a complete set of eigenvectors in the opening, each region can be represented by an equivalent Norton circuit involving a short-circuit current (a vector) and a generator admittance (a matrix). The particular case of a cavity at resonance is investigated. Application to a cavity terminated in a waveguide is considered, and the transformation of the equivalent circuit resulting from the shift of the terminal plane is analyzed. After solving the example of a slotted waveguide, a possible set of eigenvectors for an arbitrary opening is proposed.     

An X‐Band Carbon‐Doped InGaP/GaAs Heterojunction Bipolar Transistor MMIC Oscillator

This paper addresses a fully‐integrated low phase noise X‐band oscillator fabricated using a carbon‐doped InGaP heterojunction bipolar transistor (HBT) GaAs process with a cutoff frequency of 53.2 GHz and maximum oscillation frequency of 70 GHz. The oscillator circuit consists of a negative resistance generating circuit with a base inductor, a resonating emitter circuit with a microstrip line, and a buffering resistive collector circuit with a tuning diode. The oscillator exhibits 4.33 dBm output power and achieves ?127.8 dBc/Hz phase noise at 100 kHz away from a 10.39 GHz oscillating frequency, which benchmarks the lowest reported phase noise achieved for a monolithic X‐band oscillator. The oscillator draws a 36 mA current from a 6.19 V supply with 47.1 MHz of frequency tuning range using a 4 V change. It occupies a 0.8 mm × 0.8 mm die area.     

A 2 W CMOS Hybrid Switching Amplitude Modulator for EDGE Polar Transmitters

This paper presents a hybrid switching amplitude modulator for class-E2 EDGE polar transmitters. To achieve both high efficiency and high speed, it consists of a wideband buffered linear amplifier as a voltage source and a PWM switching amplifier with a 2 MHz switching frequency as a dependent current source. The linear amplifier with a novel class-AB topology has a high current-driving capability of approximately 300 mA with a bandwidth wider than 10 MHz. It can also operate on four quadrants with very low output impedance of about 200 at the switching frequency attenuating the output ripple voltage to less than 12 . A feedforward path, a PWM control, and a third-order ripple filter are used to reduce the current burden of the linear amplifier. The output voltage of the hybrid modulator ranges from 0.4 to 3 V for a 3.5 V supply. It can drive an RF power amplifier with an equivalent impedance of 4 up to a maximum output power of 2.25 W with a maximum efficiency of 88.3%. The chip has been fabricated in a 0.35 m CMOS process and occupies an area of 4.7 .     

La synthèse d’antennes à deux réflecteurs conformés à alimentation décalée

A potentially economic method for upgrading the gain of the large earth reflector antenna Cassegrain system to a gain comparable to that obtainable with a dualshaped reflector antenna system is presented herein. It involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a paraboloid. A pair of offset subreflectors are synthesized which will give a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method that is used is based on an approximate formulation for an offset dual shaped high gain antenna where the geometrical optics energy was scattered from a subreflector and then from a second large reflector which reflected a uniform phase distribution. In the present offset dual shaped subreflector (DSS) antenna, the second reflection is from a smaller subreflector and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. Excellent results are shown for the approximate synthesis of the DSS.     

Synthesis of the fields of a transverse feed for a spherical reflector

The problem of designing a transverse feed for a spherical reflector is considered and a method is presented for synthesizing the fields on a surface of a sphere enclosing a feed that will produce a specified reflected field at the surface of a spherical reflector. The method identifies the reflector and a spherical surface enclosing the feed as a boundary value problem and uses a finite set of spherical waves to approximate the boundary conditions. A feed designed to excite this field will in turn produce the desired reflected field at the surface of the reflector, under the condition that that portion of the reflected field which is scattered by the feed may be neglected. It is shown that the feed need produce only a small part of the synthesized field to obtain an antenna efficiency of more than 70 percent. Some typical field distributions will be shown so as to indicate a method for designing a feed and to point out the correlation between the polarization of the synthesized field and the polarization of the reflected field at the surface of the reflector.     

Plane wave propagation in a uniaxial bianisotropic medium with an application to a polarization transformer

Uniaxial bianisotropic medium is a generalization of the well-studied bi-isotropic and chiral media. It is obtained, for example, when microscopic helices with parallel axes are positioned in a host dielectric in random locations. Plane wave propagation in such a medium is studied and a simple solution for the dispersion equation and for the eigenwaves are found. As a numerical example, polarization properties of a transverse wave propagating in a uniaxial bianisotropic medium is considered. The results give a simple possibility to construct a polarization transformer with a transversely uniaxial chiral medium for changing the polarization of a propagating plane wave.     

Design of a high-order single-loop ∑△ ADC followed by a decimator in 0.18 μm CMOS technology

This work presents an oversampled high-order single-loop single-bit sigma-delta analog-to-digital con verter followed by a multi-stage decimation filter. Design details and measurement results for the whole chip are presented for a TSMC 0.18 μm CMOS implementation to achieve virtually ideal 16-b performance over a baseband of 640 kHz. The modulator in this work is a fully differential circuit that operates from a single 1.8 V power supply. With an oversampling ratio of 64 and a clock rate of 81.92 MHz, the modulator achieves a 94 dB dynamic range. The decimator achieves a pass-band ripple of less than 0.01 dB, a stop-band attenuation of 80 dB and a transition band from 640 to 740 kHz. The whole chip consumes only 56 mW for a 1.28 MHz output rate and occupies a die area of 1×2 mm~2.     

A 0.25-mW low-pass passive sigma-delta modulator with built-inmixer for a 10-MHz IF input

The design of a passive sigma-delta modulator without using operational amplifiers is presented. Issues of its application to IF digitization with subsampling scheme are discussed. In addition, a switch-only gain-boost network is proposed to achieve a dc voltage gain in a passive way. The prototype chip of a second-order passive sigma-delta modulator was fabricated in a 1.2-μm CMOS process. Testing results showed that with a 10-MHz IF input (bandwidth of 20 kHz), the modulator achieved a 13-b resolution at 0.25 mW with a 3.3 V power supply. Good performance was also measured with a baseband input     

Digital image watermarking employing codebook in vector quantisation

Two simple watermarking techniques for a digital image are proposed. The methods employ a codebook in vector quantisation, and can extract watermark information from a watermarked image without an original image. Simulation results show that when the codebook of a larger size is used, a reconstructed image with a watermark has better quality than that without a watermark, and, for one of the proposed methods, a watermark size and the percentage of 0 bit contained in a watermark have almost no effect on PSNR for a reconstructed image.     

A 30-GHz monolithic receiver

Several monolithic integrated circuits have been developed to make a 30-GHz receiver. The receiver components include a low-noise amplifier, an IF amplifier, a mixer, and a phase shifter. The LNA has a 7-dB noise figure with over 17 dB of associated gain. The IF amplifier has a 13-dB gain with a 30-dB control range. The mixer has a conversion loss of 10.5 dB. The phase shifter has a 180° phase shift control and a minimum insertion loss of 1.6 dB.     

A 1.8-V operation RF CMOS transceiver for 2.4-GHz-band GFSK applications

This paper describes a single-chip RF transceiver LSI for 2.4-GHz-band Gaussian frequency shift-keying applications, such as Bluetooth. This chip uses a 0.18-/spl mu/m bulk CMOS process for lower current consumption. The LSI consists of almost all the required RF and IF building blocks: a transmit/receive antenna switch, a power amplifier, a low noise amplifier, an image rejection mixer, channel-selection filters, a limiter, a received signal strength indicator, a frequency discriminator, a voltage controlled oscillator, and a phase-locked loop synthesizer. The bandpass filter for channel selection was difficult to achieve since it operates at a low supply voltage. However, because large interference is roughly rejected at the output of the image rejection mixer and a wide-input-range bandpass filter with an optimized input bias is realized, the transceiver can operate at a supply voltage of 1.8 V. In the IF section, we adopted a circuit design using the minimum number of passive elements, resistors and capacitors, for a lower chip area of 10.2 mm/sup 2/.     

A Note on Loaded Line Synthesis (Correspondence)

The purpose of this note is to present an alternate derivation of a formula for the synthesis of a loaded line. The problem is to determine the values of the normalized susceptances a and c mounted an exact quarter-wavelength apart along a uniform line. These are arranged in the order a, c, c,. . .c, a to achieve a loaded line with a given phase shift and perfect match. In order to analyze a particular line design for standing-wave ratio and phase shift over a band of frequencies on a digital computer, it is worthwhile to know the values of the susceptances to many more decimal places than one would achieve from a simple graph.     

Experimental Multiple-Channel Circuit-Switched Communications

A research model of a system for multiple-channel subrate circuit-switched digital communications is described. Three Components of a local communications system (residential or business) are the switching machine, the line, and the user's equipment. Each is briefly described and overall system operation is presented. The user's communications controller, which interfaces the digital line to the user's "devices," is described in detail. The hypothetical user is allowed a multiplicity of devices, each running at a different data rate and connected to a different "party" through the switch. Any device may itself be subclassified into a multiplicity of "virtual" devices, each with a potentially different switched connection. Research objectives include the optimal utilization of system resources, a high degree of user programmability, a friendly interface to the user (or at least a test-bed for developing one), a high degree Of system flexibility so that a variety of implementations can be tested, and a test-bed for experimental services.     

Performance analysis by simulation of floating-gate MOSFETs applied on a bidirectional associative memory architecture

Floating-gate MOSFETs (FGMOSFETs) are devices that can be electrically programmable and have a non-volatile characteristic. This feature can be adopted to configure a basic cell performing as a variable resistance that can be applied in artificial neural networks as a synapse. Based on a simple model and considering the coupling coefficient of the structure as the gain of a voltage controlled voltage source, the electrical characteristics of a floating-gate MOSFET can be simulated in PSpice and an artificial neural net, such as the bidirectional associative memory (BAM), can be implemented. Therefore a performance analysis of the net may be done with different sets of threshold voltages for the FGMOSFETs configured as a CMOS inverter used as a synapse. The objective is to know pattern pairs in a bidirectional way. The result is a correlation matrix for the BAM as a function of an electrical parameter of the devices, which is directly related to the respective matrix calculated by the matrix dot product, using the method outlined by Kosko.     

A Study on Straight-Line Tracking and Posture Control in Electric Bicycle

The development of automatic control for driving a bicycle is a challenging theme and is expected to be a human assist system. Previously, an acceleration-based method for stabilizing bicycle posture was proposed by the authors. In the experiments with this controller, the posture of the bicycle might be stabilized, but it is impossible to run on the desired trajectory, because there is no consideration with respect to a trajectory control. For the sake of expanding this system into more sophisticated equipment, a realization of the trajectory control for the bicycle is important. From the viewpoint of an assist system for human motion, a unified control of posture and trajectory brings a sophisticated function to a bicycle, and a high-performance bicycle is expected to be a convenient vehicle, similar to a small car. This paper proposes two strategies to stabilize bicycle posture and trajectory control that realizes a straight-line tracking: one is a lateral velocity controller, and the other is a steering function controller. The validity of the proposed approaches is evaluated by simulations and experiments.     

A Picture Browsing System

We describe a system for storing pictures in a database and retrieving them from a remote location over a low bit-rate channel. Even with compression techniques, it takes a long time to transmit a picture, making search for a picture of desired attributes time-consuming. Our system improves the human interaction with the picture database by constructing an auxiliary text database containing a list of attributes of each picture, a hierarchical encoder-decoder, and a light pen to select the areas of picture buildup. Picture searching (or browsing) takes place in two stages: in the first stage, knowing the required picture attributes, a user selects a subset of pictures by matching attributes to the text database; in the second stage, these selected pictures are displayed hierarchically so that a low resolution picture is reproduced first and made sharper gradually. A light pen allows the user to give priority to upgrade selected areas or reject a picture. Our techniques of hierarchical coding are simple to implement. Informal tests indicate that it is much easier to browse through a picture database using this system and that the time to retrieve a picture of given attributes decreases considerably compared to sequential picture presentation.     

Noncontact AE measurement system using acoustic microscope

The surface of a slide glass (a specimen) with a notch was set in water at the focal region of a point-focus-beam lens to detect the AE (acoustic emission) signals radiating from cracks around the notch during a three point bending test. Output signals received by a transducer with a centre frequency around 50 MHz were amplified and A/D converted at a sampling rate of 200 MHz by a digital oscilloscope. The power spectra of the output signals were compared for the two cases with and without the weight used for the application of fracturing stress on the glass specimen. AE signals with a frequency range from a few megahertz to 100 MHz were successfully detected with this system for the glass specimen mounted on a small three point bending test bench.<>