Applied Mechanics and Materials Vols. 229-231

Abstract: The prediction of the indoor radio waves propagation characteristic can be a difficult task because of the indoor environment complexity. Based on the finite difference time domain algorithm, when the monopole antenna is used as the excitation, the indoor radio waves propagation characteristic is researched by using measurment method and simulation method. The effectivity of prediction method is verified by comparing the prediction results with the measurment results. The quantitative research of this paper has certain guiding significance to the confirmation of the wireless digital communication reasonable coverage.

Abstract: The distributed multiple-input multiple-output (MIMO) radar can achieve the high- resolution capabilities of target localization by coherent processing, far exceeding the bandwidth-dependent resolution of traditional radar. The conventional beam former synchronizing the phase across the widely separated transmitting and receiving antennas creates high level sidelobes that causes ambiguity in target localization. The Capon beam former with lower level sidelobes for target localization suffers from the irreversible of the covariance matrix when the numbers of transmitting and receiving antennas increase. Thus, the Capon algorithm with diagonal loading is applied to distributed MIMO radar for target localization with lower level sidelobes. Simulation results are presented to verify the effectiveness of the proposed method.

Abstract: This paper presents a 0.18μm CMOS based Gm-C complex band-pass (CBP) filter with tuning circuit. Active-Gm-C structure with Nauta transconductor and phase-locked loop (PLL) architecture are adopted by the filter and the tuning circuit respectively which can achieve accurate frequency response. The layout size is 970μm×920μm. Under a 1.8V supply voltage, measurement results show that the pass-band gain and the ripple of the filter is 3.1dB and 3dB respectively. The bandwidth after tuning is 32.5MHz, image rejection ratio (IRR) is about 47dB, and the power dissipation of the filter is about 21.6mW.

Abstract: In this paper, a programmable gain amplifier (PGA) is designed and implemented for GPS/Galileo and WCDMA dual mode receiver using TSMC 0.18μm CMOS technology. The 0-75dB variable gain range is obtained by cascading a 0-15dB variable gain stage and four 15dB fixed gain stages. An open-loop structured fully-differential amplifier with source feedback resistor is adopted in basic gain stage. Variation of gain is achieved by switch-controlled output resistor network. Gm-boost structure is used in main amplifier. A DC-offset canceller circuit using DC negative feedback technique is proposed to eliminate the DC-offset of the PGA. Post-simulation shows that the PGA has 0-75dB variable gain range, 1dB gain resolution and less than 0.3dB gain error; the minimum DC attenuation is about 15dB over the whole gain range; -3dB bandwidth at the maximum gain configuration is about 15MHz; differential output peak to peak voltage is greater than 1V; and the entire circuit consumes about 3.6mA current under 1.8V supply voltage.

Abstract: The electromagnetic simulation software CST was used to analyze the effects of reentry plasma sheath on the GPS navigation antenna. The Impedance and radiation characteristics of antenna were studied on condition that the antenna was coated with uniform and nonuniform electron density distribution plasma sheath respectively. The results show that, the antenna coated with the uniform plasma sheath, the plasma electron density increasing, the antenna operating frequency moves to high-frequency and that the directivity decreases as well; when the antenna was coated with nonuniform plasma, with the higher electron peak density of plasma sheath, besides that the operating frequency also moves to high-frequency, the bandwidth stretches wide and the return loss reduces; the antenna radiation pattern distorts seriously at the electron peak density of 10¹⁸m^-3.

Abstract: The Archimedean spiral (ARSP) antenna is widely used in many wide band electronic systems due to its good radiation performances. This paper designed and fabricated a specific planar ARSP antenna within the operating frequency range of 1 GHz to 9GHz. The meander line technique was employed to miniaturize the planar ARSP antenna. The designed ARSP antenna was fed by a wide band miniaturized bent microstrip Balun. The diameter of the fabricated ARSP antenna was 82 millimeters. A metal cavity filled with absorber materials was used to obtain the unidirectional radiation patterns and its height was 30 millimeters. The parameters of designed ARSP antenna were determined by numerical simulations. A practical designed ARSP antenna was fabricated according to designed parameters and the experimental results of the fabricated ARSP antenna are provided. The experimental research results demonstrate that the fabricated ARSP antenna has radiation performances of wide beam and approximately circular polarization. The fabricated ARSP antenna can be used in several practical electronic systems such as wide band radar systems.

Abstract: A CPW-fed microstrip monopole antenna which is conformal to a conical surface is presented in this paper. It has a simple structure printed on a substrate with dielectric constant of 2.55 and thickness of 0.2mm. By the aid of electromagnetic simulation software of CST Microwave Studio, the main influencing parameters of the antenna are simulated and analyzed, the difference between planar antenna and conical conformal antenna has been discussed, and the optimized physical model has been achieved. The simulated result shows the proposed CPW-fed conical conformal antenna has a broad bandwidth property that covers from 6.2 to 20GHz(VSWR 2), and it is suitable for wideband radar applications.

Abstract: For CMOS circuitry the models which are able to determine the reliability of the components and the methods which lead them to the degradation of the reliability issues are very important. Negative bias temperature instability (NBTI) is a critical issue for the p-MOSFETs. It causes, shifting of drive current and threshold voltage of P-MOSFET. Till date many models capable of simulating various features of the NBTI degradation have been proposed by researchers. Reaction Diffusion (R-D) model is notable among them. This paper demonstrates a new approach which analyzes the combination of R-D model and transistor theories. To do so, we analytically correlated R-D model and device theory. The analysis shows the lifetime estimation for p-MOSFET device with respect to drain current.

Abstract: When an STM tip is brought close to a nano sized sample then it can deliver (or draw) a current that is determined by the Landauer-Büttiker formalism in terms of the scattering matrix that gives partial local density of states. We show that, very paradoxically, the interference related term in this formula vanish in a quantum regime making semi-classical formula for injectance exact in some regime. We explicitly show how evanescent modes are responsible for this. This can have useful implications to experimentalists as semi-classical formulas are much simpler.

Abstract: The relible and fast data transmission over noisy band limitted channels is the basic requirment of digital communication and transmission system. Reliability considerations require that forward error correction techniques be used. This techniques find and correct limitted erros caused by a transport or storage systems. Such coding technique is therefore used to help compensate for signal degradation and provide increase in system capacity and reliability. In this paper, we analyze the performance of three codes which are the Reed Soloman Code, the convolutional code, and turbo code for the same signal that is corrupted by transmission channel. The type of channel considered in this work is the AWGN. For the same message length, the turbo code gives the best performance and the Reed Soloman Code gave the poorest performance when the signal is corrupted by AWGN channel.