A high resolution highly linear low spur fractional time-to-digital converter (FTDC) for All Digital PLL (ADPLL) is presented. This FTDC employs a linear high gain time amplifier (TAMP) and a spur reduction digital filter to eliminate the spurs at the output. Unlike conventional TDCs, no delay line is utilized in the new FTDC, and hence no mismatch error cancelation technique is required. The FTDC structure is verified in theory and via simulation using an 180nm CMOS technology. The results illustrate a time resolution of 5psec, differential nonlinearity (DNL) free dynamic range of about 350psec, and the total power consumption, apart from the clock generator, of nearly 3mW.
A new Matrix Pencil (MP) method including mutual coupling effects based on a Uniform Linear Array (ULA) is presented. By setting a group of elements as auxiliary on each side of the ULA, it can accurately estimate the Direction of Arrival (DOA) using a single snapshot of data and the effect of mutual coupling can be eliminated by the inherent mechanism of the proposed method. Theoretical analysis and simulation results demonstrate the effectiveness of the proposed algorithm.
A large quasi-TEM waveguide for EMC testing is successfully designed by a waveguide with two artificial magnetic conductor (AMC) side-walls comprising an array of a dipole frequency selective surface (FSS) printed on a grounded dielectric slab. In this paper, characteristics of the large quasi-TEM waveguide which dimensions are equal to or larger than the wavelength are investigated. At the resonant frequency of the AMC side-walls, the phase velocity is equal to the speed of light and the electric field distribution is uniform in the large quasi-TEM waveguide. Therefore, a quasi-TEM mode has been achieved in the large quasi-TEM waveguide. In addition, by adjusting the size of the AMC structure, a large quasi-TEM waveguide can be applied to arbitrary frequency for EMC testing.
Distributed power control by beamforming approach in cognitive radio networks requires a precise analysis of the impacts of the transmission parameters, tolerable interference and guarantees the quality of service of both the primary users and secondary users. In this paper, we propose an improved performance to solve the constrained nonlinear multi-object optimization and coherent power assignment by beamforming problem based on particle swarm optimization. This method is invoked to solve the constrained nonlinear optimization problem in order to reach to maximum capacity. A numerical study is performed to show the convergence behavior of the proposed algorithm and the efficiency of the proposed technique with a dynamic cost function.
Running average is a simple and effective background modeling method that generates adaptive background image for moving object detection. Fuzzy Running Average (FRA) improves the selectivity of Standard Running Average (SRA). However, its background restoration rate is slow. This leads to false object detection when a static object becomes dynamic. To overcome this problem, an Extended Fuzzy Running Average (EFRA) is proposed. The results show that the EFRA not only retains the selectivity benefit of FRA, but also improves the restoration rate significantly.
In cognitive radio networks, allocation of the sensing duration is of critical importance for efficient spectrum sensing. Conventional optimization of sensing duration is limited in two primary channels as well as same constant thresholds for all the primary channels. In this paper, we consider multiple primary channels and formulate the problem of sensing duration allocation as a convex optimization with respect to both the sensing durations and detection thresholds. Then, based on Penalty method and Newton's method, a searching algorithm is proposed to obtain the optimal solution. We show via simulation results that our scheme substantially improves the transmission opportunity of cognitive user compared with existing ones.
A stochastic signal detection circuit that uses a non-linearity reduction technique is designed using a 65-nm CMOS process. The fabricated chip demonstrates the feasibility of stochastic signal detection at 500MS/s.
The electrical properties of Organic thin-film transistor (OTFT) with a pentacene active layer of 3nm and 50nm were examined. By a new estimation method of applied voltage in channel layer of OTFT, it was found that the ratio of potential drop to lateral direction of channel at on-state is smaller than that at off-state and also that of 3nm thickness OTFT is larger than 50nm thickness. The on-state current of 3nm thickness OTFT was larger than that of 50nm thickness. The main reason of this phenomenon is due to the difference of the resistance of hole injection from Au to pentacene. The quantum-mechanical effect is also discussed.
A fuzzy controller is suited to control Antilock Brake System (ABS) however time complexity of fuzzy controller is high order. Problem Solution Data Structure (PSDS) has been introduced as a data-oriented model of fuzzy controller to reduce the response time. Locally learning of PSDS controller has been left as an open issue. Fuzzy Learning Mechanism (FLM) has been introduced by using fuzzy inference as learning function, but it needs considerable long process time and steady state errors. In this paper an Adaptive Neuro Fuzzy Inference System (ANFIS) Learning Mechanism (ALM) to learn PSDS is presented. The simulation results show better performance of ALM PSDS comparing to FLM PSDS controller in terms of slip ratio control, stop distance, process time and reduction in steady state errors.
Flash file systems are used for flash memory-based storage devices for more efficient use of flash memory. In the file system, metadata, especially directory management, is one of the crucial management points to enhance storage system performance. In this paper, we present an efficient directory management scheme of flash memory based file system for giga scale flash memory. Specifically, we design the hash-based directory architecture for directory management and indexing structure for file index management. The hash-based directory management can reduce redundant write operations of flash memory. It can also reduce the file system mount time and memory usage during runtime.
This paper proposes the use of a beam steering scheme for establishing multicast communication between millimeter-wave devices in 60GHz wireless networks. It should be noted that beam steering is a key technique for the millimeter-wave multicast devices scattered omni directionally. We derive the analytical expression for the dynamic beamforming, and we observe the impact of the number of beams. Extensive simulation results show that dynamic beam steering enable more efficient sectoring than fixed beam steering.
Measurement results of bending diameter dependence of the crosstalk of each core in a multi-core fiber are presented. The crosstalk of cores shows different diameter dependence although the difference in core parameters is very small. The behavior is explained by taking into account the change of propagation constant caused by the fluctuation in the diameter and the refractive index of cores. The diameter dependence simulated with coupled-power theory shows the same tendency with the measured crosstalk.
We proposed and fabricated an optical spectrum control circuit using an arrayed-waveguide grating (AWG) and an array of channel waveguides with tunable phase shifters. We found that the spectral phase and amplitude of a modulated optical signal could be arbitrarily controlled if the number of channel waveguides was set to be more than twice the number of waveguides in the AWG. As a first demonstration, we successfully obtained a flat band-pass filter function with the fabricated device by controlling the tunable phase shifters to control the interference between the light propagating through them.
We have derived a novel uniform asymptotic solution for reflection of the Gaussian beam that is incident on a dielectric interface from a denser medium to a rarer one. The validity of the novel uniform asymptotic solution has been confirmed by comparing with the reference solution. It has been shown that the transition beam plays an important role to connect two different solutions smoothly through the transition region. It becomes apparent that, near the critical angle of the total reflection, the Gaussian beam is displaced to either direction by the interference between the geometrically reflected beam and the lateral beam.