Showing papers on "Switching time published in 2000"

Fast-switching frequency synthesizer with a discriminator-aided phase detector

Abstract: A phase-locked loop (PLL) with a fast-locked discriminator-aided phase detector (DAPD) is presented. Compared with the conventional phase detector (PD), the proposed fast-locked PD reduces the PLL pull-in time and enhances the switching speed, while maintaining better noise bandwidth. The synthesizer has been implemented in a 0.35-/spl mu/m CMOS process, and the output phase noise is -99 dBc/Hz at 100-kHz offset. Under the supply voltage of 3.3 V, its power consumption is 120 mW.

Magnetic stimulation coil and circuit design

Abstract: A detailed analysis of the membrane voltage rise commensurate with the electrical charging circuit of a typical magnetic stimulator is presented. The analysis shows how the membrane voltage is linked to the energy, reluctance, and resonant frequency of the electrical charging circuit. There is an optimum resonant frequency for any nerve membrane depending on its capacitive time constant. The analysis also shows why a larger membrane voltage will be registered on the second phase of a biphasic pulse excitation. Typical constraints on three key quantities voltage, current, and silicone controlled rectifier (SCR) switching time dictate key components such as capacitance, inductance, and choice of turns.

High-speed modulation and switching characteristics of In(Ga)As-Al(Ga)As self-organized quantum-dot lasers

Abstract: The dynamic characteristics, and in particular the modulation bandwidth, of high-speed semiconductor lasers are determined by intrinsic factors and extrinsic parameters. In particular, carrier transport through the heterostructure and thermalization, or quantum capture in the gain region, tend to play an important role. We have made a detailed study of carrier relaxation and quantum capture phenomena in In(Ga)As-Al(Ga)As self-organized quantum dots (QD's) and single-mode lasers incorporating such dots in the gain region through a variety of measurements. The modulation bandwidth of QD lasers is limited to 5-6 GHz at room temperature and increases to /spl sim/30 GHz only upon lowering the temperature to 100 K. This behavior is explained by considering electron-hole scattering as the dominant mechanisms of electron relaxation in QD's and the scattering rate seems to decrease with increase of temperature. The switching of the emission wavelength, from the ground state to an excited state, has been studied in coupled cavity devices. It is found that the switching speed is determined intrinsically by the relaxation time of carriers into the QD states. Fast switching from the ground to the excited state transition is observed. The electrooptic coefficients in the dots have been measured and linear coefficient /spl tau/=2.58/spl times/10/sup -11/ m/V. The characteristics of electrooptic modulators (EOM's) are also described.

Innovative micromachined microwave switch with very low insertion loss

Abstract: This work fabricates a novel type of micromachined microwave switch on a semi-insulating GaAs substrate using a microactuator and a coplanar waveguide (CPW) using electrostatic actuation as the switching mechanism. The microactuator uses several continuously-bent cantilevers connected in series. A cantilever with two sections, a straight-beam section and a curved-beam section, forms the basic unit of the microactuator. The straight-beam section is made of an aluminum (Al) layer, 0.5 μm thick. The curved-beam section is made of an Al layer of the same thickness, combined with a 0.1-μm layer of chromium (Cr) film. This section is initially curled due to the different residual stress of Al and Cr. The low temperature (250°C) process ensures that the switch is capable of monolithic integration with microwave and millimeter wave integrated circuits (MMIC). When no dc potential is applied, the actuator is curled far from the signal line of the CPW, and therefore the insertion loss at this `on' state is only 0.2 dB at 10 GHz. Because the metal microactuator is far from the signal line of the CPW at this `on' state, the microwave propagation is hardly disturbed by the microactuator. When an applied electrostatic force pulls the actuator tip down into contact with the signal line of the CPW, it creates a large capacitance between the actuator and the CPW. The isolation at this `off' state is −17 dB at 10 GHz. Maintaining the actuator in the `off' state requires only a very low actuation voltage of 26 V. Once the dc potential is removed, the residual stress of the actuator structure pulls it to the up position. The microactuator moving back and forth between these two switching states, acts like the movement of a frog's tongue. This switch has excellent performance at the wide-band RF frequencies used in transmit/receive modules of wireless communication. This study measured the critical corrupt (activating) voltage and recovery voltage of the microactuator. The 10-ms switching time of this switch is slower than the switching time of solid-state switches.

An electrostatically-actuated MEMS switch for power applications

Abstract: This paper presents the design, analysis, fabrication, and testing of an electrostatically-actuated MEMS power switch. The device can be switched electrostatically (20 V), pneumatically (1200 Pa), or through combined actuation. Prototype switches carry currents in excess of 400 mA in either current direction with a contact resistance as low as 14 m/spl Omega/. Their off-state resistance is higher than the 30 M/spl Omega/ limit of the test equipment. Breakdown voltages of 300 V have been achieved across their small air gaps. Their nominal switching time is 20 ms. Extended lifetime testing has not been carried out but our tests to date show that the prototype switches operate more than 4000 cycles without significant degradation in their contact resistance. Finally, a protective switching scheme is proposed to minimize contact wear due to arcing during switch opening and closing.

Optimal Control of a Class of Linear Hybrid Systems with Saturation

Abstract: We consider a class of first order linear hybrid systems with saturation. A system that belongs to this class can operate in several modes or phases; in each phase each state variable of the system exhibits a linear growth until a specified upper or lower saturation level is reached, and after that the state variable stays at that saturation level until the end of the phase. A typical example of such a system is a traffic signal controlled intersection. We develop methods to determine optimal switching time sequences for first order linear hybrid systems with saturation that minimize criteria such as average queue length, worst case queue length, average waiting time, and so on. First we show how the extended linear complementarity problem (ELCP), which is a mathematical programming problem, can be used to describe the set of system trajectories of a first order linear hybrid system with saturation. Optimization over the solution set of the ELCP then yields an optimal switching time sequence. Although this method yields globally optimal switching time sequences, it is not feasible in practice due to its computational complexity. Therefore, we also present some methods to compute suboptimal switching time sequences. Furthermore, we show that if there is no upper saturation, then for some objective functions the globally optimal switching time sequence can be computed very efficiently. We also discuss some approximations that lead to suboptimal switching time sequences that can be computed very efficiently. Finally, we use these results to design optimal switching time sequences for traffic signal controlled intersections.

Damped gyromagnetic switching

Abstract: The gyromagnetic switching behavior of a single-domain grain or particle with uniaxial magnetocrystalline and shape anisotropy is solved analytically by the gyromagnetic torque equation using physically plausible Gilbert damping. The sole restriction is that the anisotropy easy axis and the applied field be collinear. The analytical solution for the magnetization switching time is then used to calculate precisely various phenomena which occur in pulsed-current stripline testing of magnetic recording storage media. Also, the analytic relationship between the polar and azimuthal angles of the magnetization during damped precession is derived.

Self-aligned micromachining process for large-scale, free-space optical cross-connects

Abstract: A new micromachining process for large-scale optical cross-connects is presented. It satisfies the high-accuracy optical alignment required for free-space optics. A self-aligned batch-process allowing the simultaneous fabrication of vertical mirrors and fiber guides is performed with only one-mask. This process is based on bulk micromachining of [100] silicon. A first demonstration is performed on a 2/spl times/2 elementary cell then, it is extended to the fabrication of larger mirror arrays. Promising performances such as insertion loss lower than 0.5 dB, sub-millisecond switching time (0.3 ms) and reliable operation (more than 20 million cycles) are demonstrated on a bypass switch. An improved fabrication process, leading to an increase of integration density is also presented. It is based on the combination of deep dry-etching and anisotropic wet-etching.

Coupled U-shaped cantilever actuators for 1×4 and 2×2 optical fibre switches

Abstract: Thermally-driven coupled cantilever actuators for multistable switching in micromechanical 1×4 and 2×2 optical fibre switches are presented. The coupled U-shaped cantilevers for a lateral movement of fibres eliminate angular displacements. The clamp mechanism for multistable switching makes use of an H-shaped buckling platform and results in latching type switches. The coupled U-shaped actuators are thermally-driven with a power of approximately 350 mW and 1 W for the 2×2 switch and the two outer fibres of the 1×4 switch, respectively. The power needed for the two inner fibres of the 1×4 switch corresponds to the 2×2 switch behaviour. A switching time of 300 ms has been achieved so far. The first fabricated micromechanical 2×2 and 1×4 switches show good optical properties with insertion losses less than or equal to 1 dB and a crosstalk less than -60 dB. The fabrication is based on full-wafer micromachining using V-grooves both for fibre alignment and for cantilever formation in {100} silicon.

Apparatus and method for automated band selection via synthesizer bit insertion

Abstract: A method and apparatus for providing time-critical band selection in a communication device with dual band or multi-band switching, or, alternatively, for providing dual mode or multi-mode time critical operating ability. The mobile station typically has a transmitter section and a receiver section each capable of dual modes of operation, a frequency synthesizer and a controller. The band to band operating method utilizes a frequency command data signal where data derived from the signal is used in a determinable bit stream of data including a frequency data word. The frequency data word is used for defining an operational state of the synthesizer frequency thereby implementing the transceiver's operating channel. At least one bit (or functional bits) from within the bit stream or received signal is used for defining, at least momentarily, the transceiver's “new” operating band (or state). The functional bits can also be used to effectuate other time critical operations of the mobile station, including band to band switching operations (such as MAHO) over two distinct frequency bands; or, one or more can be used to switch or enable control circuits or functions or operations which are time limited or time constrained or which implicate time critical operations of the communication device or apparatus.

Silicon micro optical switching device with an electromagnetically operated cantilever

Abstract: We report on a new concept 2×2 fiber-optical switching device with an electromagnetically operated cantilever. The device is composed of a switching mirror module and a fiber array module. The switching mirror module consists of a fixed mirror, a moving mirror, a cantilever, support glasses and magnets. The mirrors and the cantilever are micromachined from one silicon wafer by deep silicon etching. As the cantilever has a magnetic film on its surface, it is driven by an electromagnet and latched by permanent magnets. The fiber array module consists of four optical fibers with graded index fibers, which are aligned parallel and fixed in a glass holder. The required current to operate the cantilever is 34 mA (0.3 V) and 20 ms for the pulse width, and the required magnetomotive force is 9.5 A·turns. The shortest switching time is 20 ms. The surface roughness of the mirrors are about 30 nm, the reflection loss of one mirror is −0.05 dB, crosstalk is smaller than −60 dB, and the insertion loss is −1.5 dB. Owing to the optical fibers preassembled as a module, the proposed device facilitates the optical path adjustment and the assembly.

Low phase noise ring-type voltage controlled oscillator

Abstract: A delay stage used in a ring-type voltage-controlled oscillator has an inverter, a memory element, and tuning circuitry. The memory element is coupled to the output of the inverter to delay the time before the inverter's output begins to switch states in response to the inverter's input switching states. The tuning circuitry receives a control voltage and is coupled to the inverter to alter the strength of the inverter without altering the strength of the memory element. Altering the strength of the tuning circuitry alters the delay of the delay stage, and hence the frequency of the VCO's operation. Because the strength of the memory element is not altered, the speed at which the inverter's output switches remains substantially constant at all tuned frequencies. The switching speed is primarily dictated by the FT of the process.

Free space communication link using a grating light modulator

Abstract: This paper presents the design and operation of a free space communication link based on a grating light modulator (GLM) in a corner cube reflector configuration. A GLM is a micromachined optical phase grating whose grating efficiency can be controlled electrostatically. Combining the GLM with a corner cube to create a grating corner cube (GCC) modulator reduces the alignment requirements of the device. Our device has a measured acceptance angle of ≈6° in the plane of incidence of the GLM, limited by angle dependence of the grating. Significant improvement of the acceptance angle can be achieved by optimizing the layer thickness of the grating structure. The resonance frequency of our GLMs is 290 kHz. Their low damping leads to ringing that increases the switching time to 35 us. The ringing has been reduced using a pre-shaped actuation signal yielding switching times of 10 μs. Low misalignment sensitivity, low power consumption, and low switching times make the GCC ideal for use in free space optical communication links.

Electrooptic and Dielectric Properties in Bent-Shaped Liquid Crystals

Abstract: Electrooptic and dielectric properties were studied in the antiferroelectric phase, B2, of bent-shaped liquid crystal molecules. We have succeeded in selectively obtaining the homogeneously chiral domain, the racemic domain, and the intermediate domain in which layers with opposite chirality are partially mixed, by properly choosing particular waveforms of the electric field applied. Tristable switching was observed for all domains under a triangular wave field. The switching current profiles under a rectangular wave field indicate that the switching time of homogeneously chiral domains is slower than that of racemic domains. The magnitude of spontaneous polarization depends not on temperature but on the carbon number of the terminal chain of the molecules. Two relaxation modes were detected in dielectric measurements, one of which was attributed to the distortion of the antiferroelectric ordering.

On the response speed of pi-cells

Abstract: We discuss the role of the Miesowicz viscosities on director reorientation in pi-cells, showing that the symmetry of this system allows for a simplification of the dynamical equations. We consider practical aspects of material optimisation for increased pi-cell switching speed. We make an observation regarding the switching speeds of positive and negative dielectric anisotropy surface mode devices.

Micro-opto-mechanical grating switches

Abstract: This paper reports the design, fabrication, and testing of a Micro-opto-mechanical grating switch driven by electrostatic actuator for fiber-optic communication applications. It consists of two bounded silicon wafers. One input fiber with a hemispherical lens at its end and three photodetectors are mounted on the upper wafer. A movable platform with two gratings and one mirror are fabricated on the lower wafer. When the movable platform is at a certain position, the input beam can be split into three beams by the gratings. The reflectivity of the mirror is about 85% while the efficiency in the three different order is 29%, 26%, and 26%. The switching speed is about 500 μs. Details of the grating switching design, theoretical analysis, fabrication and experimental results are presented in this paper.

The Mott Transition Field Effect Transistor: A Nanodevice?

Abstract: A field effect transistor device (FET), consisting of a nonlinear Mott Insulator channel material, and a high dielectric-constant gate oxide, is explored as a nanoscale device. Experimental functionality of a large scale prototype (5 μm channel length) has been demonstrated. The underlying physics of the device is analyzed and modeled using a time-dependent Hartree approach. Timing estimates suggest a relatively short switching time.

Switching properties of SrBi2Ta2O9 thin films produced by metalorganic decomposition

Abstract: The process of polarization reversal in a SrBi2Ta2O9 (SBT) thin film capacitor produced by a metalorganic decomposition method was investigated. The switching time (100–600 ns) and the reversible polarization have been measured at different voltages in the range of 0–5 V. It was found that by annealing the SBT sample in AR atmosphere at 400 °C, the switching times were significantly reduced. This indicates that oxygen vacancies in the film speed up nucleation and growth of new domains.

1/spl times/8 micro-mechanical switches based on moving waveguides for optical fiber network switching

Abstract: The feasibility of 1/spl times/N switches based on moving waveguides has been demonstrated. Solutions have been developed to overcome the technological hurdles encountered. The elementary 1/spl times/2 switch performances have been strongly improved: very low crosstalk (<-42 dB), low optical losses (1.5 dB), insensitivity to wavelength (<0.2 dB, 1250-1650 nm wavelength range) and polarisation (<0.3 dB), low driving voltage (<70 V), low switching time (<5 ms). Due to the results associated with a size reduction and a very accurate and reproducible control of residual deflection, we have demonstrated that the fabrication of larger 1/spl times/N switches is possible by cascading 1/spl times/2 switches. 1/spl times/8 switches have been fabricated. Moreover an 8/spl times/8 switching matrix has been demonstrated using arrays of 1/spl times/8 switches. These demonstrations show that this technology can address the different switching applications.

A mechanical shutter for light using piezoelectric actuators

Abstract: The design and performance of a mechanical shutter for laser light based on low voltage piezoelectric transducers is described. By focusing the beam through a pair of piezo-mounted slits, a transmission of 80%, a switching time of 10 μs, and an extinction ratio of 300:1 are obtained.

Asymmetric Switching of Ferroelectric Polarization in a Heteroepitaxial BaTiO3 Thin Film Capacitor

Abstract: Asymmetric switching of ferroelectric polarization was measured and analyzed for a heteroepitaxial BaTiO3 thin film of 58 nm thickness. The BaTiO3 film prepared on a SrRuO3/SrTiO3 substrate by radio-frequency magnetron sputtering has a c-axis oriented normal to the surface which is 3% longer than that of the bulk due to lattice misfit between SrRuO3 and BaTiO3. When positive and negative voltage pulses of the same amplitude were sequentially applied, asymmetric responses were observed in the transient current. Although the switching charge densities Qsw were the same for both the polarities, the switching time ts was longer and the peak current imax was smaller for the positive response. From the analyses of the transient current, the asymmetric switching of polarization was attributed to the discrepancy in coercive voltages Vc between polarities.

Subsampling digitizer-based frequency synthesizer

Abstract: A reduced phase noise multiplication, digitally controlled frequency synthesizer employs a subsampling digitizer to downconvert (perform ‘constructive aliasing’ of) the synthesizer's output frequency to baseband for precision tuning of the synthesizer's output frequency in a digitally controlled phase locked loop. The use of a digitally controlled phase locked loop allows the stepsize of the synthesizer output frequency to be controlled in very small (e.g., sub-Hertz) increments. Since the phase locked loop uses all digital components for tuning control, no additional frequency division by the loop is required. This means that only the value of the subharmonic ratio ‘n’ of the subsampling clock to the analog-to-digital converter will determine multiplicative phase noise error.

Self aligned vertical mirrors and V-grooves applied to a self-latching matrix switch for optical networks

Abstract: This paper reports a new and low cost method of fabrication for M*N matrix switch using wet etching of silicon: a self-aligned batch process allowing the fabrication of vertical mirrors and V-grooves is performed in one-level of mask in [100] silicon wafer. The feasibility of a self-latching system with electromagnetic force is shown for the actuation of switch. Promising performances such as insertion loss lower than 0.5 dB, submillisecond switching time (0.4 ms) and reliable operation (20 > million cycles) are achieved.

Intrinsic Josephson effect and single Cooper pair tunneling

Abstract: We proposed a new, small and fast switching gate based on the intrinsic Josephson effect of single crystals of a cuprate superconductor The switching time is of subpicosecond order, and the operating frequency is up to several terahertz We used the focused-ion-beam (FIB) method for the fabrication of small Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) stacked intrinsic Josephson junctions (IJJ) with in-plane size down to the submicron level without the degradation of their T c We observed clear Fraunhofer patterns in I c – B curves and flux-flow velocity of up to 10 6 m/s for the stack junctions with the size of several micrometer scale For the submicron junction, the low-temperature behavior is governed by the Coulomb-charging effects This is the first observation of the Coulomb-charging effects in layered high- T c materials

Switching circuit having a switching semiconductor device and control method thereof

Abstract: The present invention provides a switching circuit and an electronic switching component having a switching semiconductor device to perform switching between a conducting state and a non-conducting state of a conducting path to thereby reduce the power loss thereof and a control method thereof. In the present invention, at least two FETs 11 and 12, wherein the FET 11 has a faster switching time and the FET 12 has a lower ON resistance. Active terminals (drains and sources) of the FETs 11 and 12 are connected to each other in parallel. By employing these FETs 11 and 12, the conversion between an ON-state and an OFF-state of the conducting path is performed. In converting from the non-conducting state to the conducting state, the control circuit 13 first turns on the FET 11 and then turns on the FET 12 when if a voltage between terminals of the FET 11 reaches around a saturation value thereof. In converting from the conducting state to the non-conducting state, the control circuit 13 first turns off the FET 12 and then turns off the FET 11 when if a voltage between terminals of the FET 11 reaches around a saturation value thereof.

Windowing scheme for analyzing noise from multiple sources

Abstract: Method and apparatus for detecting and analyzing effects of noise in a digital circuit that arises from a coupling of signals produced by switching of a first gate and a second gate in a timed relationship. Where each of a first gate and a second gate can switch within a selected switching time interval, the gate switching effects are combined and the second gate output signal is analyzed with reference to the first gate input signal. Otherwise, the gate switching effects are not combined. When the second gate output signal satisfies at least one of three criteria, this condition is interpreted as indicating that the second gate permits propagation of a noise pulse produced at the first gate.

CoolMOS-a new approach towards system miniaturization and energy saving

Abstract: The CoolMOS Technology from Infineon is in most cell electrical parameters superior to the conventional power MOSFET. The entire and very easy variation of switching time di/dt- and dv/dt values open up a wide area in the application from extremely fast switching to the soft switching behaviour. Ruggedness aspects such as avalanche behaviour are excellent. The overall dynamic behaviour gives an outstanding MOS-controlled device.

Phase-locked loop frequency synthesizer

Abstract: A phase-locked loop frequency synthesizer includes circuitry which determines the real gain of a voltage-controlled oscillator from at least one measurement parameter and delivers a signal representative of the real gain of the voltage-controlled oscillator.

Kick-down switching speed optimization for an automatic transmission of a motor vehicle

Abstract: In the method for kick-down switching speed optimization in a motor vehicle with an automatic transmission, the kick-down upshift point is determined as a function of the load conditions and the road inclination in each case.

Peak hold and calibration circuit

Abstract: The present invention generally relates to a peak hold and calibration circuit, and more particularly, to a peak hold and calibration circuit for use in measuring the signals in a digital multi-meter implemented by using an integrated circuit (IC) and a capacitor, wherein said IC is connected to said capacitor; wherein said IC comprises an operational amplifier, and a switching circuit; wherein a first voltage is applied to one input terminal of said operational amplifier and the other input terminal of said operational amplifier is connected to the feedback network while the output terminal of said operational amplifier is connected to said switching circuit; wherein the output of said switching circuit is a second voltage and connected to said capacitor. The peak hold and calibration circuit for use in measuring the signals in a digital multi-meter of the present utilizes only a few components, thus it has lower fabricating cost, higher economic profit, low power-consumption and can solve the problems in that the diode which has short switching time, small parasitic capacitance, and small leakage current is hardly found.