Integrated Pulsewidth Modulation Control for a Scalable Optical Switch Matrix

In this paper, a pulse width modulation (PWM) generator based on a switched capacitor for LCD backlight brightness control is described. The proposed scheme uses a simple RC network along with a clocked-comparator which samples the output of the ambient light sensor, and generates a PWM signal corresponding to the light level. Furthermore, by using a switched-capacitor resistor with variable clock frequency, the RC time constant is programmable and less sensitive to process variations with respect to passive resistors. In addition, it is shown that the linearity of the proposed PWM generator can be enhanced by replacing the RC network resistor with a constant current source. The operation of the PWM generator is verified through circuit level simulations, and the prototype circuit is fabricated using CMOS 0.18um technology.

The first fully integrated GaN pulse width modulation (PWM) generator for power conversion applications is presented in this paper. The solution is implemented in a 0.5-μm technology, avoiding additional pins and external capacitors for sawtooth signal generation while providing high accuracy. Indeed, the large GaN process spreads are addressed through an innovative dynamic offset compensation approach whose clock signal takes advantage of the PWM signal itself. The proposed PWM generator adopts a 6-V power supply and includes a 25 digital divider to set the PWM frequency at 500 kHz and the minimum and maximum duty cycles at 6% and 94%, respectively. Experimental results on integrated prototypes validated the correct circuit functionality over the temperature range from -40°C to 120°C. As a main achievement, this work demonstrates effective all-GaN integration of complex mixed analog and digital circuits, thus representing a significant advancement in the approaches to overcome the main limitations of GaN devices and enable fully integrated signal processing implementation.

As product complexity continues to increase, test engineers are challenged with improving test coverage on a variety of devices while keeping costs at a minimum. When finished products incorporate hundreds or thousands of devices, developing and maintaining separate test systems for individual components lacks scalability. An approach to this problem is to standardize on a single platform and develop a small number of test systems that can each test tens or hundreds of different devices. Test engineers are increasingly seeing the benefits of developing, deploying, and supporting a reduced number of test systems that use common components. Although many factors such as system assurance and platform longevity influence the long-term success of these systems, the core requirements consist of modular, reconfigurable hardware. A switching matrix is the main hardware component that gives a single test system the flexibility to test a variety of devices. With a switching matrix, you can connect all of your instruments and test points through a series of relays and close relevant relays via software. Switching matrices provide several benefits such as simple connectivity and test repeatability; however, it's usually not practical to have a switching matrix that completely matches the I/O of your instruments. For example, if you have a 1,000 V DMM, a 2 A power supply, and a 1.5 GHz digitizer, you're unlikely to find a COTS switching matrix that maximizes those I/O points. Selecting a switching matrix involves evaluating various trade-offs between density, power, bandwidth, and so on and optimizing the cost of your test system. This paper examines the trade-offs you should evaluate when choosing a switching matrix along with considerations for reducing cost and size.

This paper proposes new solutions for implementing wideband large switch matrices. These solutions are based on crossbar and L-shaped topologies. This paper introduces a high-performance wideband switch cell to build up scalable NtimesN switch matrices and gives an account of the design, fabrication, and characteristics of the switch cell and a 3times3 crossbar switch matrix. The chosen design procedure is seen to be appropriate since it produces valid measured results. In addition, this paper presents an RF microelectromechanical systems L-shaped switch matrix, which indicates less variation of characteristics for certain types of connectivity. It also demonstrates that for a 4times4 switch matrix, there is a 50% improvement in insertion loss and phase-shift variation.

Current electronic broadband switch matrices employ discrete semiconductor devices or VLSI chips. Isolation between ON- and OFF-states degrades and crosstalk between input and output lines of these electronic switch matrices increases at high operation frequencies. These will limit electronic switch matrices to low-frequency or low-bit-rate operations. In addition, optical-to-electrical (electrical-to-optical) conversions at the input (output) ends are required for these switch matrices to be used in a fiber environment. One way to achieve broadband, low-crosstalk, and high-isolation switching and to eliminate E/O and O/E conversions is to use optical switches. This paper describes an optical broadband switching architecture using optical/optoelectronic logic gates. Input and output signals are optical. No E/O or O/E conversions are needed for this architecture. The optical/optoelectronic logic gates that can be employed in this architecture are reviewed. Performance of this architecture is evaluated by calculating the crosstalk, isolation, insertion loss, switch matrix size, drive power, and switching speed. Technologies needed for hybrid and monolithic implementations of this architecture are also identified.

The cross-connect architecture using star couplers, wavelength converters and optical switch matrices is the simplest of the many architectures proposed so far. The authors demonstrate a design criterion for attaining a strictly non-blocking network between any wavelength and spatial channels.

With the increased commercial availability of high channel count MR coil arrays and the associated higher number of plugs in the patient bed, it has become a common practice to include switch matrices in the receive path of MR systems. These allow the arbitrary routing of a signal from any plug to any receiver in the console. While switch matrices are standard in systems at clinical field strength and have been developed for systems operating up to 4T, they have not yet been implemented at ultra-high field (UHF). Here, we present a switch matrix suitable for operation at UHF. Crossbar switches, which are the most frequently employed forms of a switch matrix, use RF switches to connect horizontal input lines with the desired vertical output line. This leaves transmission line stubs of variable length physically connected with the selected signal path, potentially resulting in elevated signal losses. While this can be tolerated at low frequencies, and only needs partial compensation at intermediate frequencies (4T), a full compensation is required at UHF. In this study, an RF crossbar switch, which uses switchable compensation elements in both horizontal and vertical transmission lines, was implemented for a 9.4T MRI scanner. The prototype developed was evaluated for single channel and multichannel receive performance and benchmarked against a fixed wire connection.

In a generic switching problem, a switching pattern consists of a one-to-one mapping from a set of inputs to a set of outputs (i.e., a permutation). We propose and investigate a wireless switching framework in which a multi-antenna relay is responsible for switching traffic among a set of N stations. We refer to such a relay as a MIMO switch. With beamforming and linear detection, the MIMO switch controls which stations are connected to which stations. Each beamforming matrix realizes a permutation pattern among the stations. We refer to the corresponding permutation matrix as a switch matrix. By scheduling a set of different switch matrices, full connectivity among the stations can be established. In this paper, we focus on “fair switching” in which equal amounts of traffic are to be delivered for all the N(N - 1) ordered pairs of stations. In particular, we investigate how the system throughput can be maximized. In general, for large N the number of possible switch matrices N! is huge, making the scheduling problem combinatorially challenging. We show that for N = 4 and 5, only a subset of N - 1 of the N! switch matrices need to be considered in the scheduling problem to achieve good throughput. We conjecture that this will be the case for large N as well. This conjecture, if valid, implies that for practical purposes, fair-switching scheduling is not an intractable problem.

Integrated optics switch matrices are expected to play an important role in optical space switching systems due to their ability to route information practically irrespective of its bandwidth and coding format (” code and frequency transparency”), in marked contrast to electronic switching networks. The integrated optics switches also offer the advantage of integration, as opposed to mechanical optical switches. Accordingly a number of integrated optics matrices have been reported1,2,3. However , all of these have been polarization sensitive, requiring interfacing to non-standard polarization holding fibers, and this can be considered a major factor in complicating systems applications. Ref4describes a polarization independent 1×16 switch in the tree structure employed below, however with strict fabrication tolerance on the switches. One reason for staying with polarization sensitive matrices has been the difficulty to combine integratability (reasonably low voltage -length product) with high yield for low crosstalk switch points. Here we report a matrix based on a switch point which combines these features by electronic tuning of its switching characteristics, relaxing fabrication tolerances5. The switch points are further arranged in a tree structure6,7which combines the capability for communicative as well as distributive switching with relaxed requirements on the crosstalk of each switching point. This is achieved at the expense of the number of switches: The 4×4 matrix reported in this paper (Fig 1) comprises 24 switches as opposed to the 16 switches of a crossbar structure, but the number of cascaded levels is only 4, as opposed to 7 in the crossbar case.

Large-scale optical switching matrix is the core technology of automatically switched optical network. With the significant increase of the matrix size, the study showed that the nonlinear factors, such as the correlation of the wavelength, phase and polarization between the optical switches have major impacts for the system performance. Because the full-size optical simulation is not available now, the research will be a great significance that we establish an overall model with not only considering the performance of optical switch unit, but also reflecting the structural characteristics of the network.In this paper, we calculated the transmission field of 2×2 Mach –Zehnder(MZI) silica on silicon thermo optic(TO) switch with different structure by using the finite difference beam propagation method(BPM). On the basis of optimization design, we constructed and simulated the large-scale 16×16 MZI silicon-based SiO2 Silica on silicon thermo switching matrix. The results are: In TE Mode, for Crossbar and banyan structures, insertion losses are 13.35 dB and 4.3638 dB; crosstalk losses are 27.125~29.0173 dB and 42.2318-43.7159 dB; extinction ratios are 29.57 dB and 26.79 dB respectively.

This paper presents a simple and novel generalized pulse width modulation (GPWM) algorithm for voltage source inverter fed induction motor drives. The classical space vector approach requires angle and sector information for the calculation of switching times, which increases the complexity of the PWM algorithm. Hence, to reduce the complexity, the proposed GPWM algorithm generates the modulating signals by using the instantaneous phase voltages only. In the proposed algorithm, a unique zero sequence signal is added to the instantaneous phase voltages in order to generate the modulating waveforms. By varying a constant in the zero sequence signal from 0 to 1, various PWM algorithms such as space vector PWM (SVPWM) and discontinuous PWM (DPWM) algorithms are generated. Moreover, a simple overmodulation algorithm is also presented in this paper. Thus, the proposed GPWM algorithm generates all possible PWM algorithms in the entire modulation region. To validate the proposed algorithm, several simulation and experimental results are presented and compared. The results show the best agreement with the published work.

Construction of large scale switch matrix by interconnecting integrated optical switch chips with EDFAs

High-speed low-drive power guided-wave optical matrix switches should perform various functions in future wideband multichannel integrated and fiber optic systems. An integrated optical switching matrix (network) was first described by Taylor(1) and a 4x4 switching network was later realized in a LiNbO3 substrate using five stepped Δβ reversal directional-coupler switches(2) by Schmidt.(3) In this paper we will report on an electrooptical channel waveguide matrix switch which utilizes total internal reflection (TIR) in a Y-cut LiNbO3 substrate. We will first present the performance characteristics of a basic channel waveguide TIR switch which is an improved version of the one we reported earlier.(4) We will then describe the design, fabrication, measurement technique, and the performance characteristics of a 3x3 and a 4x4 integrated switching matrices consisting of such basic TIR switches.

This paper investigates a novel optical multicast scheme without excess optical splitting loss to be realized using an active vertical coupler (AVC)-based optical switch matrix, due to the optical gain available in the AVC switch cells. Theoretical analysis and computer simulation have been carried out regarding the operational principle and switching characteristics of this scheme. Computer simulation further suggests that the amplified spontaneous emission (ASE)-limited scalability of the scheme can be as high as more than 40. Experiments using an existing 4 /spl times/ 4 switch-matrix device successfully demonstrated the predicted multicast switching operation. Measured switching characteristics and the optical signal-to-noise ratio (OSNR) values are in good agreement with simulation predictions. High switched-signal Q-factor values of 1-to-2 and 1-to-3 multicasting configurations indicate that the scale of the multicasting scheme can be further increased significantly.

Optical switch matrices are important devices in communication systems due to their frequency and code transparency. Several such matrices have been demonstrated, most of them, however, exhibiting different levels of blocking. For many systems applications a strictly nonblocking matrix (i.e., one where established signal paths do not need rearrangement when a connection between unoccupied ports is established) is preferable. The busbar structure, shown in an 8 × 8 version in Fig. 1, fulfills this requirement. Any of the eight upper (lower) inputs can reach any of the eight upper (lower) outputs by switching the appropriate cross-point.