Time-Mode Signal Quantization for Use in Sigma-Delta Modulators

A design of a 5.6 GHz frequency synthesizer with switched bias LIT VCO and low noise on‐chip LDO regulator for 5G applications

Multi-band RF front-ends with adaptive image rejection : a DECT/Bluetooth study case

Several integrated capacitors can be used in analog-to-digital converters (ADCs) for complementary-metal-oxide-semiconductor (CMOS) image sensors, including metal-insulator-metal (MIM), metal-oxide-metal (MOM) and metal-oxide-semiconductor (MOS) capacitors. Among those capacitors, MOS capacitors have the highest capacitance density per unit area but a large voltage dependency, which will cause the non-linearity of ADCs. Recently, several types of ADCs are employed for column-parallel ADCs, including a single-slope (SS), sigma-delta (ΔΣ), successive approximation (SAR) ADC, cyclic ADC and folding-integration/cyclic (FI-Cyclic) ADCs. A Cyclic ADC is well known for its ability to achieve medium resolution while requiring a small silicon area and implementing a reasonable conversion rate of one conversion cycle per bit of resolution. Compared with other ADCs, the cyclic ADC has superiority in overcoming the difficulty of compatibility between ADC speed and bit resolution, while maintaining low-noise and HDR. On the basis of inheriting the advantage of cyclic ADC, FI-Cyclic ADC has better performance on low noise, high grayscale resolution and resulting high dynamic range.

A numerical study of magnetohydrodynamic flows and heat transfer past a circular cylinder in a duct under a strong magnetic field parallel to the cylinder axis is presented. In this configuration, the flow is quasi-two-dimensional and the modified Navier–Stokes equations are solved in a two–dimensional domain. The numerical simulations have been performed over a range of parameters including the Reynolds number 50 ≤ Re ≤ 3000, modified Hartmann number 50 ≤ Ha⋆ . 500, blockage ratio 0.1 ≤ β ≤ 0.5, offset ratio 0.25 ≤ γ ≤ 1, velocity amplitude 0 ≤ A ≤ 3 and forcing frequency 0 ≤ Ste ≤ 10. The primary aim of this study is to understand the fundamental mechanism that governs transition to unsteady flow in this system and exploit this for further improvements in heat transfer for MHD cooling duct flows. With this aim in mind, a spectral-element method is employed to compute the MHD flow and heat transfer past a confined circular cylinder in a rectangular duct. Meshes have been constructed to deal with the significant number of geometric flow parameters combinations. Thorough validation and grid resolution studies have been performed to ensure adequate domain sizes, and spatial and temporal resolutions to accurately resolve all flow and thermal features for the reported flow variable ranges. Studies show that the reported flow parameters are converged to better than 0.3% in terms of spatial and temporal accuracy and 1% with respect to the domain size. For the optimal growth studies, the dependence of energy growth on upstream domain length is also considered through the calculation of the energy growth over a fixed time span. This verifies that the effect of truncating the upstream length from 32d to 8d causes an error of less than 3% in the growth rate prediction. The critical Reynolds number Rec for the transition from steady to periodic flow is determined as a function of Ha⋆ and β, and this is found to increase with increasing Ha⋆ and β. In addition, the variation of the wake recirculation length in the steady flow regime is determined as a function of Reynolds number, Hartman number and blockage ratio, and a universal expression is proposed. The characteristics of heat transfer depend strongly on the proximity of the cylinder to the heated wall. For small blockage ratios, it increases significantly as the gap ratio decreases from 1 to 0.25. However, there is a substantial drop in heat transfer for high blockage ratio. Downstream cross-stream mixing induced by the cylinder wake is found to increase the heat transfer augmentation by more than a factor of two in some cases. The maximum gain in heat transfer generated by placing the cylinder in the channel near to the wall with that at the centerline was obtained for the lowest blockage ratio β = 0.1, as the cylinder is further approached the heated wall. For all β, a very significant transient energy growth is found in the subcritical regime below the onset of vortex shedding. This suggests a potential for the design of an actuation mechanism to invoke vortex shedding and then enhance heat transfer in these ducts. The energy amplification of the disturbances is found to decrease significantly with increasing Hartmann number and the peak growth shifts towards smaller times while it increases significantly with increasing blockage ratio. The structure of the optimal initial disturbance is found to be consistent across the all blockage ratios being tested. In line with similar problems, it convects along the separating region being amplified to the peak growth state downstream of the recirculation bubble. The maximum time for maximum energy growth τmax is found to increase significantly as recirculation length increases which demonstrates the amplifying nature of the separated shear layers in the wake. The critical Reynolds number for the onset of positive growth at different Hartmann numbers and blockage ratios is determined. It is found that it increases rapidly with increasing Hartmann number and blockage ratio. For all β, the peak energy amplification grows exponentially with Re from low Hartmann numbers. Direct numerical simulation studies in which the inflow is perturbed by random white noise confirms the predictions arising from the transient growth analysis: that is, the perturbation excites and feeds energy into the global mode. A considerable increase in heat transfer from the heated channel wall occurs from rotational oscillation of the cylinder, with a maximum enhancement of approximately 22% observed at higher amplitude over that for steady flow. The oscillation frequency range for effective enhancement is widened in both directions, while the frequency at which the peak of the Nusselt number occurs is shifted slightly to a lower frequency as A is increased. It is found that as the amplitude was reduced, the forcing frequency approaches the global frequency mode.

In previous work, a complete dynamic inflow model for flow above the rotor disk has been developed; and numerical results have been presented in both the frequency domain and the time domain. In this paper, we extend the inflow model to all three components of inflow below the disk. The inflow model, which is expressed in terms of a finite number of states, is derived in a mathematically rigorous way. The essence of the extension is that if one computes the co-states of the inflow equations (along with the normal states), then one can find the velocity in the hemisphere below the plane of the rotor disk (including the velocity within the wake) with accuracy equal to that of the flow above the rotor plane. The derivation is for the case of general skew angle. Numerical comparisons with exact solutions for the z-component of flow in axial flow––given for some special cases––illustrate the effectiveness of the new model. The simulations also illustrate that the model is valid for either the frequency domain or the time domain. Nomenclature n m a : real part for cosine induced inflow expansion coefficients n m b : imaginary part for cosine induced inflow expansion coefficients [ ] D :

In this paper a new digital background calibration method for successive approximation register analog to digital converters is presented. For developing, a perturbation signal is added and also digital offset is injected. One of the main advantages of this work is that it is completely digitally and eliminates the nonlinear errors between analog capacitor and array capacitors due to converter’s capacitors mismatch error by correcting the relative weights. Performing of this digital dithering method does not require extra capacitors or double independent converters and it will eliminate mismatches caused by these added elements. Also, No extra calibration overhead for complicated mathematical calculation is needed. It unlike split calibration, does not need two independent converters for production of two specified paths and it just have one capacitor array which makes it possible with simple architecture. Furthermore, to improve DNL and INL and correct the missing code error, sub radix-2 is used in the converter structure. Proposed calibration method is implemented by a 10 bit, 1.87-radix SAR converter. Simulation results with MATLAB software show great improvement in static and dynamic characteristics in applied analog to digital converter after calibration. So, it can be used in calibration of successive approximation register analog to digital converters.

Abstract— A 2.5 V feed-forward second-order delta-sigma modulator for audio application is presented. A 9-level quantizer with a tree-structured dynamic element matching (DEM) was employed to improve the linearity by shaping the distortion resulted from the capacitor mismatch of the feedback digital-to-analog converter (DAC). A chopper stabilization technique (CHS) is used to reduce the flicker noise in the first integrator. The prototype delta-sigma analog-to-digital converter (ADC) implemented in a 65 nm 1P8M CMOS process occupies 0.747 mm 2 and achieves 109.1 dB dynamic range (DR), 85.4 dB signal-to-noise ratio (SNR) in a 24 kHz audio signal bandwidth, while consuming 14.75 mW from a 2.5 V supply. Index Terms —Delta-sigma modulator, feed-forward, dynamic element matching, chopper stabilization I. I NTRODUCTION Recent advances of CMOS technology have enabled the high quality signal processing in the multi-media and communication systems and have resulted in a great demand for the high resolution analog-to-digital converters (ADCs). Among various ADC architectures, the delta-sigma ADC offers high dynamic range by using oversampling and noise shaping properties. Moreover, as it requires only simple and relatively high-tolerance analog components with fast and complex digital signal processing to achieve high resolution, it is very well-suited for the digital CMOS process. The theoretical signal-to-quantization noise ratio (SQNR) of the delta-sigma ADC is given by Eq. (1)

We propose a cost effective digitized radio-over-fiber (D-RoF) system employing a sigma delta modulation (SDM) and a bidirectional transmission technique using phase modulated downlink and intensity modulated uplink. SDM is transparent to different radio access technologies and modulation formats, and more suitable for a downlink of wireless system because a digital to analog converter (DAC) can be avoided at the base station (BS). Also, Central station and BS share the same light source by using a phase modulation for the downlink and an intensity modulation for the uplink transmission. Avoiding DACs and light sources have advantages in terms of cost reduction, power consumption, and compatibility with conventional wireless network structure. We have designed a cost effective bidirectional D-RoF system using a low pass SDM and measured the downlink and uplink transmission performance in terms of error vector magnitude, signal spectra, and constellations, which are based on the 10MHz LTE 64-QAM standard.

Accurate prediction of loads on mechanical couplings is crucial in assessment of loads on coupled structures, and in reliable prediction of the motions of coupled bodies. This thesis presents a numerical articulation method, which is capable of modeling various mechanical couplings. The proposed numerical method relies on contact elements. The first objective of the work is to prove the eligibility of contact elements in representation of mechanical couplings, and to highlight the shortcomings and positive aspects of contact elements for this representation. The second objective of the thesis is to study the influence of different hydrodynamic, kinematic, and coupling models on the motion behavior of articulated bodies and coupling forces. To accomplish these objectives extensive and systematic studies on a twofold pushing convoy are conducted. The convoy bodies are interconnected with hinge joints. The hinges are modeled by means of kinematic constraints, and with contact elements. Frequency and time domain boundary element methods with linearized motions of equation, as well as a Reynolds-averaged Navier-Stokes (RANS) code coupled with a nonlinear kinematic solver are used to compute the body motion responses and coupling forces. The simulation results are compared to model basin measurements. It is shown that the contact element model can simulate mechanical couplings efficiently and it provides a suitable method to idealize free and suppressed modes at articulation locations. Furthermore, it is shown, that RANS in association with the nonlinear equation of motion and kinematically constrained joints, as well as boundary element methods in adherence to the contact element model provide more accurate prediction of articulation forces, and motion responses of coupled bodies. However, frequency and time domain boundary element methods with kinematically constrained joints still deliver agreeable and reliable results. Moreover, a case study is presented, in which a river-sea pushing convoy is applied in time domain numerical simulations. The convoy bodies are interconnected with prismatic joints and are free to heave and pitch relative to each other. Prismatic joints are modeled by means of contact elements. The case study demonstrates a successful application of contact elements in simulation of complexly articulated multibody systems. Furthermore, the findings obtained in this work contribute sustainably to the numerical approaches in assessment of hydrodynamic and articulation loads on mechanically coupled floating bodies.

The differentiated services (DS) architecture provides a framework for the scalable provisioning of multiple service levels in the Internet. Its definition and initial work have concentrated mainly on per-hop behaviors (PHB) and mechanisms at each DS domain. Equally important is what happens between DS domains. Thanks to the flexibility of the architecture, it is the providers’ choice how to interconnect with peers. In principle, traditional, static peering agreements work together with DS, but they do not offer the flexibility and dynamics needed in an electronic market for network capacity. Therefore, we look at dynamic service level agreements at the interdomain level. Such agreements are established by software entities called traders. These traders follow market-based principles to decide which contracts will be beneficial. In particular, traders compare the offers made by neighbor providers and select the most interesting ones. This selection of peer services creates competition among providers and integrates route selection based on service level and destination. We describe and implement a framework for service level agreement trading. We show the basic workings and first performance results of SLA trading using specific traders and an experimentally defined PHB in a simulation environment. Keywords— Network architecture, differentiated services architecture, service level agreement, pricing, trading, interdomain QoS routing.

This paper deals with specification and design methodology of analog to digital converter (ADC) stage for high dynamic range wide band multistandard radio receiver. To respect high resolution requirements a sigma-delta (/spl Sigma//spl Delta/) modulator based ADC is proposed. A high dynamic range low complexity 1-bit sigma-delta modulator is designed to guarantee high linearity for GSM/UMTS signals. Hence, a novel stable 3/sup rd/ order 1-bit low-pass /spl Sigma//spl Delta/ modulator is defined. Simulation results show more than 90 dB dynamic ranges for GSM and 60 dB for UMTS.

The repetitive processing and large quantity of single product represented by 3C products are urgently needed. However, for current processing operations, previous processing data have not been used in the optimization of control input. In order to utilize previous processing data to facilitate the next process and avoid adverse effects caused by repetitive disturbance and noise, the idea of iterative learning was introduced to improve the accuracy of machining. On the control level, since it is difficult to obtain high accuracy by traditional feedback control when faced with complex trajectories, an open-loop iterative learning controller and a position loop feedback controller were introduced, which worked fast with good convergence effects. Aiming at reducing the influence of accidental error, step type iterative learning was put forward. The iteration mechanism was stopped when the accuracy converged to the allowable range so as to reduce computational complexity, store the current iterative part of the control input, and make constant value compensation. However, in simulation and experiment, it was found that after superposition of the iterative learning controller, the phenomenon of partial divergence of the system tracking error occurred. Therefore, the speed and acceleration characteristics of input trajectories in time domain and frequency domain were analyzed. High-frequency noise was introduced in frequency domain, which was found to be the cause of the abovementioned phenomenon, and high-frequency components were filtered to solve the problem. To further improve the accuracy of convergence and avoid filtering effective high-frequency information in some area, a switchable filter based on the analysis of the frequency characteristics of input trajectory was proposed. Through SIMULINK simulation and dSPACE experimental verification, it was proved that the iterative learning controller of modifying controlled quantity and filter based iterative learning control method are effective.

Low-power systems are essential for Internet-of-Things (IoT) applications powered by harvested energy or batteries, such as wearable devices, structural health monitoring, industrial process monitoring, and personal health monitoring. Analog to digital converter (ADC) is an essential part of the IoT sensor interface and communication system that receives analog signals such as radio waves, light, sound, and biological signals. Depending on the purpose, the ADC is designed for the targets of low voltage operation, dynamic voltage scaling, and high resolution. The technology and supply voltage scaling caused by technological advances reduce voltage headroom and signal power, which makes it challenging to achieve high performance in analog circuit design. A voltagecontrolled oscillator (VCO) based ADC that processes analog information in the time domain can be desirable for technology and supply voltage scaling.

PT Insan Persada as a company engaged in the field of waterproofing contractor with a broad scope of projects and many are located outside the city requires optimal IT involvement so the need for a mechanism appropriate IT governance standards. COBIT 4.1 framework provide solutions to implement IT governance model. This study focuses on the domain of the domain that washy and organise PO4 (determining the IT processes, organization and relationship), PO5 domains (managing IT investments), PO7 domain (IT human resource management), domain PO8 (managing quality), and the domain PO9 (assess and manage IT risks). This research using the method management awareness and maturity level in each domain of each PO4, PO5, PO7, PO8 and PO9. Based on calculations using the performance level of management awareness on PO4 domain has an average value of 1:22 (approximately), PO5 domain with an average value of 1.90 (moderate), PO7 domain with an average value of 1:46 (approximately), with a mean value PO8 domain average 1.67 (medium) and PO9 with an average value of 1:38 (approximately). While the calculation of the level of maturity assessment using the domain PO4 maturity level is 1 (initial/ad hoc), PO5 domain is 2 (repeatable but intuitive), PO7 domain is 2 (repeatable but intuitive), PO8 domain is 2 (repeatable but intuitive) and domain PO9 is 1 (initial/ad hoc). From the results of these studies indicate each is still not optimal for each domain and each domain has a gap that must be addressed as a form of recommendation on the proposed research. Keywords: Plan and organise, Management Awareness, Maturity Level, Waterproofing

Sigma-delta modulation is a common technique used in analog-to-digital conversion. It has been shown that it can be implemented in a field-programmable gate array (FPGA) using minimal external analog components. Zhao et al. demonstrated that energy of scintillation pulses can be computed by adding up all the elements on the output from a conventional 1-bit sigmadelta modulator. However, for parameters selected for a suitable resolution and dynamic range, the system passes through a period of saturation. During saturation, information about the shape of the pulse is lost even though the integrated energy remains preserved. We present the design of a 2-bit version of the sigmadelta modulator that makes use of a nonlinear adaptive digital-to-analog converter (DAC) that keeps the system unsaturated. Each output bit is scaled by one of the four possible values the DAC can take, resulting in a 2-bit modulation. We have demonstrated that the 2-bit modulation retains information about the pulse shape.