Power efficiency enhancement analysis of an inverse class D power amplifier for NB-IoT applications

Analog Integrated Circuits and Signal Processing - The power amplifiers (PAs) are generally the most power-consuming building blocks in Radio Frequency (RF) transceivers. This paper presents a high...     

Acquisition of high-precision images for non-contact atomic force microscopy

The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. The distance between cantilever tip and sample surface in non-contact AFM is a time-varying parameter even for a fixed sample height, and typically difficult to identify. A remedy to this problem is to directly identify the sample height in order to generate high-precision atomic-resolution images. For this, the microcantilever (which forms the basis for the operation of AFM) is modeled as a single mode approximation and the interaction between the sample and cantilever is derived from a van der Waals potential. Since in most practical applications only the microcantilever deflection is accessible, we will use merely this measurement to identify the sample height. In most non-contact AFMs, cantilevers with high-quality factors are employed essentially for acquiring high-resolution images. However, due to high-quality factor, the settling time is relatively large and the required time to achieve a periodic motion is long. As a result, identification methods based on amplitude and phase measurements cannot be efficiently utilized. The proposed method overcomes this shortfall by using a small fraction of the transient motion for parameter identification, so the scanning speed can be increased significantly. Furthermore, for acquiring atomic-scale images of atomically flat samples, the need for feedback loop to achieve setpoint amplitude is basically eliminated. On the other hand, for acquiring atomic-scale images of highly uneven samples, a simple PI controller is designed to track the desired constant sample height. Simulation results are provided to demonstrate the feasibility of the approach for both sample height identification and tracking the desired sample height.     

Low-voltage and low-power Ku-band CMOS LNA using capacitive feedback

Analog Integrated Circuits and Signal Processing - An ultra-wideband (12–18 GHz) low-noise amplifier (LNA) using a 65 nm CMOS technology is proposed, in which a...     

Analysis and Design of a Phase-Tunable Source Injection-Coupled LC Quadrature Oscillator

This paper presents the design and analysis of phase-tunable injection-coupled quadrature oscillator (PT-IC-QO). Like other LC QOs, the mismatches between LC tanks are the main source of phase error in this oscillator. Using tail current in network coupling is novel approach to design new IC-QO. One of the advantages using added extra tail current in coupling network is control of coupling factor and also that it drastically reduces supply noise over classic IC-QO. Analysis and simulation result show that phase error can be controlled and cancelled simply by using tunable tail current in network coupling while that is difficultly controlled in the previse work. The basic idea of the presented design to reduce phase error due to tank mismatches is its compensation with an intentional mismatch between \(I\hbox {/}Q\)-side injection current. Based on the equations, a new tunable source-injected QO is proposed which is able to cancel the phase errors up to \(\pm 20^\circ \), without undesirable impact on phase noise. To evaluate the proposed analysis and consequent designed quadrature oscillator, a 5.4-GHz CMOS PT-QO is designed and simulated using the practical \(0.18\,\upmu \hbox {m}\) TSMC CMOS technology.     

Estimation of lung's air volume and its variations throughout respiratory CT image sequences

A respiratory image-sequence-segmentation technique is introduced based on a novel image-sequence analysis. The proposed technique is capable of segmenting the lung's air and its soft tissues followed by estimating the lung's air volume and its variations throughout the image sequence. Accurate estimation of these two parameters is very important in many applications related to lung disease diagnosis and treatment systems (e.g., brachytherapy), where the parameters are either the variables of interest themselves or are dependent/independent variables. The concept of the proposed technique involves using the image sequence's combined histogram to obtain a reasonable initial guess for the lung's air segmentation thresholds. This is followed by an optimization process to find the optimum threshold values that best satisfy the lung's air mass conservation and tissue incompressibility principles. These threshold values are consequently applied to estimate the lung's air volume and its variations throughout respiratory Computed Tomography (CT) image sequences. Ex vivo experiments were conducted on porcine left lungs in order to demonstrate the performance of the proposed technique. The proposed method was initially validated using a breath-hold CT image sequence with known air volumes inside the lung, where results show that the proposed technique outperforms single-histogram-based methods. This was followed by demonstrating the proposed technique's application in a 4-D-CT respiratory sequence, where the air volume inside the lung was unknown. Consistency of the obtained results in the latter experiment with tissue near incompressibility principle was validated. The results indicate a very good ability of the proposed method for estimating the lung's air volume and its variations in a respiratory image sequence.     

A time-domain noise-coupling technique for continuous-time sigma-delta modulators

In this paper, a time-domain noise-coupling technique based on the pulse width modulation is proposed. The time-domain quantization error is digitally extracted and shaped by an asynchronous digital filter. This digitally filtered quantization error is applied to the quantizer input to increase the modulator’s noise-shaping order. By using this technique in continuous-time sigma-delta modulators, the modulator’s shaping property is significantly enhanced. Comparative analytical calculations and simulation results are presented to estimate the performance of modulators employing the proposed quantizer. System-level simulation results reveal a (L + 2)th order noise-shaping capability of the proposed modulator while it employs only L analog integrators. The effects of main circuit non-idealities in the modulator’s performance are analytically investigated and confirmed by the simulation results.     

New methods for enhancing fine acquisition in dual folding algorithm of long pseudo noise codes

Long code Direct Sequence Spread Spectrum is a good choice for applications where security and antispoofing ability of a spread spectrum connection is concerned. Due to long period of spreading code, acquisition is a challenge for these systems because a trade‐off between detection probability and acquisition time must be made. For confronting this challenge, various algorithms were proposed in the literature but almost all of them focus on expediting the coarse acquisition. In this paper, we consider the efficient dual folding algorithm for coarse acquisition level and propose 3 methods for enhancing the fine acquisition level leading to faster execution of overall acquisition algorithm. The methods are based on estimations from coarse acquisition level that are not used in conventional algorithms for fine acquisition, ie, zero padding. Theoretical expressions of 2 main comparison criteria in acquisition algorithms, ie, detection probability and mean acquisition time, are derived for conventional zero padding and each of the proposed method. Besides, a coarse estimate of resource consumption is provided by the number of floating point operations for each algorithm to make a useful comparison. Considering these 3 parameters, in comparison, the proposed methods surpass zero padding in 1, 2, or all of the 3 aspects. Simulation agrees well with analytical results.     

POLAROGRAPHIC CHARACTERIZATION OF AROMATIC STRUCTURES IN COAL LIQUID PRODUCTS

Reducible aromatic species in coal liquid products from five major processes (Synthoil, FMC COED, HRI H-Coal, PAMCO SRC, and Catalytic Inc. SRC) together with solvent elution chromatography fractions of a selected asphaltene has been evaluated. The half-wave potentials measurments are found to be consistant with other methods. The total polarographic reduction of measurement per average molecule for Synthoil solvent fractions, as measured by diffusion constant (i_d/C), increases in the following manner: gas oil → resin → asphaltene → carbene → carboid. The same trend was observed when color indices (I) and refractive indices (n₂₅) were individually studied.