Modulator Topology Research Articles

On Maximal Chains in the Lattice of Module Topologies

Let (R,τ R ) be a topological ring and R M, a left unitary R-module. The set L(M) of all (R,τ R )-module topologies on R M is a complete modular lattice. A topology τ∈L(M) is n-premaximal if in L(M) there exists an inclusion-maximal chain τ0>τ1>...> τ n such that τ0 is the largest element in L(M) and τ n =τ. Section 1 contains conditions for existence of 1-premaximal Hausdorff topologies on R M; Section 2 contains a description of all n-premaximal topologies in the case when (R,τ R ) is a topological skew field whose topology is determined by a real absolute value.

Magnetoresistive tunnel junctions deposited on laterally modulated substrates

Co/Al 2 O 3 /NiFe tunnel junctions were deposited on misoriented silicon substrates. A thermal treatment activates a step bunching mechanism on the silicon surface leading to a modulated topology with a nanometric lateral period. The bottom magnetic electrode and the barrier follow this topology. Such junctions present good magnetotransport characteristics with a magnetoresistance about 14% at room temperature. Due to the uniaxial anisotropy induced by the topological modulation, the antiparallel configuration of the magnetization is well defined leading to perfect square magnetoresistance cycles at all temperatures. The magnetic behavior of patterned junctions has been investigated by transport measurements and Kerr microscopy. More than inducing a strong uniaxial anisotropy, the modulated topology is shown to strongly influence the switching mechanism of the magnetization.

A 2D CMOS microfluxgate sensor system for digital detection of weak magnetic fields

This paper presents a CMOS two-dimensional (2-D) vector magnetic sensor system integrating two planar microfluxgate sensors and the complete electronics for sensor excitation and signal readout. The system is based on an industrial 0.8-/spl mu/m double-poly, double-metal CMOS technology with ferromagnetic NiFeMo cores added in a simple postprocessing sequence. The fluxgate sensors are embedded in a /spl Sigma//spl Delta/ analog-to-digital converter for a stable and precise digital detection of weak magnetic fields. A cascaded /spl Sigma//spl Delta/ modulator topology is utilized to obtain second-order noise shaping and to suppress pattern noise. Within the range of /spl plusmn/50 /spl mu/T, the system nonlinearity is less than 1.5 /spl mu/T. The angular resolution as a 2D vector sensor is less than 4/spl deg/ for a measured magnetic induction of 50 /spl mu/T. This makes the 2-D microfluxgate magnetometer suitable for use as fully integrated electronic compass.

Comparison of series and parallel optical modulators for microwave down-conversion

Photonic down-conversion of microwave signals using a pair of broad-band optical modulators is investigated theoretically and experimentally for cascaded and parallel modulator topologies. Improvement of 14 dB, roughly equal to the composite modulator insertion loss, was measured. Low-biasing and balanced detection in parallel links allows a further improvement of over 20 dB through increased laser power without detector saturation.

A 900-mV low-power ΔΣ A/D converter with 77-dB dynamic range

The design of a low-voltage and low-power /spl Delta//spl Sigma/ analog-to-digital (A/D) converter is presented. A third-order single-loop /spl Delta//spl Sigma/ modulator topology is implemented with the differential modified switched op-amp technique. The modulator topology has been transformed as to accommodate half-delay integrators. Dedicated low-voltage circuit building blocks, such as a class AB operational transconductance amplifier, a common-mode feedback amplifier, and a comparator are treated, as well as low-voltage design techniques. The influence of very low supply voltage on power consumption is discussed. Measurement results of the 900-mV /spl Delta//spl Sigma/ A/D converter show a 77-dB dynamic range in a 16-kHz bandwidth and a 62-dB peak signal-to-noise ratio for a 40-/spl mu/W power consumption.

Alternative topologies for sigma-delta modulators-a comparative study

This paper investigates four frequently used modulator topologies, namely two single-stage and two multistage architectures. Simple parametric expressions are derived which describe minimum amplifier gain and bandwidth requirements for all implementations as well as C-ratio matching conditions for the two multistage circuits. The cumulative effect of all amplifier nonidealities, including slewing, is revealed by a discrete-time simulator. This study not only presents accurate quantitative results that illustrate the negative impact of the most stringent amplifier nonidealities but also provides the necessary insight to circumvent or minimize these parasitic effects which ultimately limit performance.

Modeling and experimental verification of the interconnected mesh power system (IMPS) MCM topology

A new low-cost multichip module (MCM) topology, the interconnected mesh power system (IMPS), has been shown capable of reducing the metal layers of a conventional four-layer MCM by half. To provide a complete MCM on only two metal layers, the IMPS topology provides a unique and complex power distribution system and signal transmission environment. This paper reports on models of the IMPS structure based on finite-difference/partial-inductance methods and PSpice simulation. The models can easily he constructed using a commercial three-dimensional (3-D) field solver and the circuit models can be solved by PSpice. The agreement between the modeled and measured results is excellent. Discrepancies between models and results are also discussed.

A prototype recipe management system in batch processes

A prototype knowledge-based system for recipe management in batch chemical processes is presented in this paper. The recipe management system (RMS) consists of three main modules: a plant topology module (PTM), a product recipe module (PRM) and a recipe transformation module (RTM). The PTM was designed to represent the equipment units in the process flowsheet and the PRM was designed to represent the recipes defined in SP88 Part 1 (draft 10). The RTM was designed to carry out the task of recipe transformation. The mechanism of the RMS is demonstrated through two examples and the results have clearly demonstrated that the challenge of efficient recipe transformation and management can be solved using object-oriented programming and artificial intelligence techniques.

Sigma-delta modulators for high-resolution and wide-band A/D converter applications

High-resolution and wide-band sigma-delta (∑Δ) A/D converters are based on high-order single-stage or cascade modulators and, more recently, also on multibit topologies. This paper reports a comparative study of the most promising modulator topologies available today, paying special attention to a new class of cascade multibit topologies that we have developed which do not require multibit D/A converters. Comparisons are made in terms of design and implementation complexity, sensitivity to amplifier dc-gain and matching between components, thermal noise, amplifier slew-rate and bandwidth, and D/A converter linearity. Design examples are given showing that 12-bit, 14-bit and 16-bit ∑Δ A/D converters with 4 MHz, 1 MHz and 150kHz output rates respectively are possible using state-of-the-art silicon technologies.

A stable high-order delta-sigma modulator with an FIR spectrum distributor

A stable high-order delta-sigma modulator topology is presented. The topology can be completely stabilized for arbitrary order by a finite impulse response (FIR) spectrum distribution technique. The stability of the modulator is examined by means of the root locus method. The topology inherently has less sensitivity to component mismatch, and can be realized without any hardware penalty compared to noise-shaping integrators of the same order. The modulator realizes 16-b resolution at 20-kHz bandwidth when a filter order of four and an oversampling ratio of 64 are employed. >

On the lattice of linear module topologies

We study various features of the lattice LM of linear module topologies on a module M and their impact on the structure of the abstract module. A particular emphasis is given to: a) permanence properties of 1- minimal topologies (=atoms in the subset of LM of Hausdorff topologies) in analogy with the theory of minimal topological groups; b) the usual equivalence between linear topologies and the equivalence classes of the atoms; c) characterization of the abstract modules M such that certain classes in LM are singletons (in particular, modules such that each non-discrete linear topology is topologically artinian). Point c) involves the class of modules having all proper quotients artinian.

Third-order cascaded sigma-delta modulators

A sigma-delta modulator architecture wherein third-order noise shaping is achieved with relatively modest constraints on device matching is explored. The architecture is based on a cascade of a second-order modulator stage followed by a first-order stage, both using 1-b quantization. To improve the dynamic range, the input to the second stage is generated as an asymmetrically weighted error signal from the first stage. An analytical model for assessing the performance and device matching requirements of cascaded architectures is introduced, and computer simulations are used to verify the approximations made in this model. The analytical model is used to show that the proposed architecture offers performance comparable to other third-order cascaded sigma-delta modulator topologies, while being less sensitive to device matching errors. >

Module Design for VLSI - heuristics to optimize layout topology

This paper presents a new method to automate essential parts of modular VLSI custom design. Our approach is dedicated to the design of bit-slice structures such as a data path of a microprocessor built up from basecells [1,2,3]. We propose three heuristics optimizing the module's topology by computing an appropriate sequence of basecells. Due to this optimization the routing expenditures are minimized. Experimental results are discussed.