Pentacene based organic field-effect transistors (OFETs) with SiO2 and HfON gate insulators have been fabricated, and the effect of deposition temperature and deposition rate on the grain sizes of pentacene films was investigated. It was found that the grain sizes of pentacene films increase with increasing deposition temperature and decreasing deposition rate. Due to the increase in grain size, pentacene based OFET with HfON gate insulator shows enhanced electrical properties, such as a low subthreshold swing of 0.14V/decade and a large on/off current ratio of 1.1×104. Moreover, the hole mobility of pentacene based OFET with HfON gate insulator is 0.39cm2/Vs at an operating voltage of -2V.
An approach to reduce side lobe level (SLL) & back lobe level (BLL) of a printed helical antenna (PHA) is investigated. The strip width is periodically changed by linear and exponential function. Two linear and exponential types of printed antennas is simulated, fabricated and measured.
Power consumption and Static noise margin (SNM) are most important parameters for memory design. The main source of power consumption in SRAM cell is due to large voltage swing on the bitlines during write operation. To reduce the power consumption and enhance the performance of the SRAM cell, we propose a Low-power fast (LPF) SRAM cell. The cell is simulated in terms of power, delay and read stability. The simulated result shows that the read and write power of the proposed cell is reduced up to 33% and 57.12% at 1.2V (in CMOS 0.12µm technology) respectively compared to the 6T cell. The read SNM of the LPF cell is 2x times of the conventional cell.
In this paper, inverse mode operation of class-J amplifier is introduced. Performances such as dc power dissipation, ac output power, and drain efficiency of the inverse mode class-J are compared with the ones of regular class-J operation. Because of the reduced overshoot in the drain current, the minimum drain voltage in inverse class-J mode can be lowered, so that the output power and drain efficiency are improved. The analysis shows that better efficiency is achieved as the minimum drain voltage is lowered below the knee voltage. For the verification, class-J and inverse class-J power amplifiers at 900MHz are implemented. The experimental results show that the efficiency of the inverse class-J amplifier is 66.2% whereas the conventional class-J operation shows 61.2%. This work is expected to be useful for the design of efficient power amplifiers with reasonable linearity.
A near-capacity Time Hopping (TH) Pulse Position Modulation (PPM) based Ultra Wide Band (UWB) Impulse Radio (IR) system is proposed, which invokes iteratively detected Self-Concatenated Convolutional Codes (SeCCC) employing Extrinsic Information Transfer (EXIT) charts. The TH-PPM-UWB-IR-SeCCC system configuration is capable of operating within about 0.9dB of the information-theoretic limits.
In order to fabricate metal gate/high-k gate stacks utilizing ECR sputtering, selective etching of HfN gate electrodes was investigated. It was found that etching rates of HfN gate electrodes at room temperature were 2.9 and 0.23nm/s for DHF (1%) and the mixed solution of HF:H2O2:H2O = 1:2:40, respectively. In addition, the etching selectivity for HfN/HfSiON was relatively high, such as the ratio of 65 which was 3 times higher than that of DHF (1%) by the mixed solution. After the in-situ formation of HfN/HfSiON layers on p-Si(100) and post deposition annealing (PDA), pattering of HfN was carried out utilizing the selective etching process. In case the PDA of 800°C/15s, the MOS diodes were found to be successfully fabricated, and the equivalent oxide thickness (EOT) of 0.56nm, and the leakage current at VFB-1 V of 1.3A/cm2 were obtained.
In this paper, we propose a new localized quality of service routing (LQSR) protocol with service differentiation, for wireless sensor networks. Reliability, real time and energy efficient data forwarding are considered in proposed routing protocol. LQSR uses modular design architecture wherein different units operate in coordination to provide multiple QoS services. Data requirements are made visible to the framework using two bits in the packet header. Simulation results show that the protocol is efficient regarding QoS parameters and has significant improvements over several geographical and QoS-based routing protocols.
The generalized normal-Laplace (GNL) distribution is employed to reflect the heavy-tailed and impulsive nature of the multiple access interference (MAI) plus AWGN noise in ultra-wideband (UWB) systems. To accurately represent the impulsive feature of the MAI-plus-noise while keeping longer tails, the kurtosis matching (KM) method combined with the method of moments estimation (MME) is proposed for the parameter estimation for time-hopping UWB multiple access communications in AWGN channels. The GNL based UWB receiver using the KM approach outperforms the conventional matched filter receiver, the soft-limiting receiver, the Gaussian-Laplace mixture receiver, and the MME-based GNL receiver in high SNR ranges.
A low-phase-noise wide-tuning-range K-band voltage-controlled oscillator (VCO) is presented in this paper. By employing accumulation MOS (AMOS) varactors deposited between drain and source terminations of the cross-coupled pair, the tuning mechanism are enhanced, leading to a boosted VCO tuning range. Moreover, the phase noise can be improved due to the better cyclostationary noise property. Based on this architecture, the fabricated VCO in 0.18-µm CMOS exhibits a measured 18.2% tuning range. Operating at 0.6-V supply voltage, the VCO consumes 2.28-mW dc power excluding the buffers. The measured phase noise is -112.53dBc/Hz at 1-MHz offset from 24.68-GHz oscillation frequency. Compared to the recently published K-band 0.18-µm CMOS VCOs, it is observed that the proposed VCO can simultaneously achieve low phase noise, wide tuning range, and low dc-power dissipation.
A novel dual-band two layered printed antenna for an internal laptop antenna for WLAN operation is presented. The antenna has a simple two layered structure consisting of a spiral strip. The proposed antenna has a low profile and can easily be fed by using a 50Ω microstrip line. It is believed that the size of the antenna is about the smallest among the existing internal laptop antennas for 2.4/5GHz WLAN operation. The antenna occupies a small area of 5mm×12mm on a combined FR4 and foam substrates. The simulated results are in good agreement with the measured results. Compact size, low cost, ease of fabrication and good radiation parameters respect to the previous designs are the most important advantages of the proposed antenna.
In this letter, a cooperative spectrum sensing scheme for cognitive radio networks based on genetic algorithm (GA) is proposed. The proposed scheme lies in optimizing the weighting coefficients vector used in a linear soft-decision fusion- (SDF-) based framework. The detection performance of the proposed GA-assisted SDF-based scheme is compared with the conventional SDF schemes as well as the OR-logic hard-decision fusion (HDF) scheme. The simulation results show that the proposed scheme outperforms all other schemes and can achieve higher probability of detection given the same probability of false alarm.
Identification and modeling of parasitic components in power electronics circuit has become a notable issue for electromagnetic compatibility (EMC) design to achieve faster and higher-frequency switching operations. This paper characterizes and models the dynamic behavior of circuit components with reflectometry measurement in a time domain. To this end, Prony analysis is applied to the TDR measurement data. The proposed method readily identifies the model order and is tolerant to measurement noise.