Vandana Nath

Mitigation of Atmospheric Turbulence in Free Space Optics: A Review

This paper reviews the work done for modeling and mitigating the effect of atmospheric turbulence and fog in the Free Space Optics (FSO). The various models proposed in recent times have been discussed and analyzed. The strengths and weaknesses of the scheme have been highlighted, providing the reader with a well rounded holistic picture of the work done in this area. The paper discusses an example to show the best mitigation technique related to Signal to noise ratio and Bit error rate (BER) based on data mining results.

Silicon carbide based DSG MOSFET for high power, high speed and high frequency applications

In this paper, High Power Double Surrounding Gate(DSG) MOSFET with 4H-SiC as material has been studied. Also, the RF performance of DSG MOSFET has been investigated for various channel length and the results so obtained are compared with the conventional Surrounding Gate(SG) MOSFET, using ATLAS 3D device simulator. From the analysis, it is shown that cylindrical Double Surrounding Gate(DSG) MOSFET exhibits superior power and analog performance than conventional cylindrical Surrounding Gate(SG) MOSFET. DSG MOSFET has a number of desirable features, such as higher transducer power gain, better current gain, high on-state current, improved transconductance gm, high unity-gain frequency fT. The improvement is due to formation of two conducting paths because of the presence of two gates. Power has further been improved because Silicon Carbide has been used as material instead of Silicon.

Design and simulation of tri-band spidron fractal equilateral triangle microstrip antenna

This paper is aimed at proposing an equilateral triangle microstrip patch antenna (ET MA) having Spidron fractal shape at one of its corners. The multiple resonance phenomenon of fractal geometry by repeating the similar segments in the radiating patch, is used in the proposed structure. Several iterations of Spidron fractal structure are simulated and analyzed. It is evident from the simulation results that the resonant frequency of the patch decreases after every iteration. The fourth iteration on the proposed antenna structure makes it suitable for operating in three different frequency bands and hence, suitable for wireless communication devoted to C (6.15-6.28 GHz), X (9.26-9.62 GHz), and Ku (12.08-15.71 GHz) band applications. Miniaturization up to 62.78% is also achieved for the proposed antenna structure, making it appropriate candidate for several wireless applications. The proposed antenna structure has an optimized dimension of 18×26 mm2. The antenna characteristics such as reflection coefficient, radiation patterns, and radiation efficiency obtained by the proposed fractal antenna confirm to its effectiveness for these applications.

Introducing Multiband and Wideband Microstrip Patch Antennas Using Fractal Geometries: Development in Last Decade

This paper deals with an extensive review of incorporating compactness, multiband and wideband features in microstrip patch antennas and their arrays using electrodynamics of various fractal shapes. A fractal geometry uses self-similar or its own scaled down replica for increasing the perimeter of given shape. This gives rise to increased current length leading to miniaturization. Different fractal shapes like Minkowski Island, Koch snowflake, Sierpinski carpet, Sierpinski gasket, crossbar tree, and several polygonal shapes and their hybrids are discussed in this paper. Applications of these fractal shapes in the field of modern wireless systems are also discussed. This paper also incorporates quantitative analysis involved in achieving miniaturization and multiband properties of microstrip antennas due to fractalization.

A numerical model of GaN based cylindrical junctionless gate all around MOSFET for subthreshold region at cryogenic temperatures

In this paper, a temperature dependent numerical model for Subthreshold region has been developed for Surface Potential, Subthreshold Current and Subthreshold Slope of GaN Junctionless (JNT) nanowire MOSFET. The effect of cryogenic temperature on the above parameters has been examined. The analytical results are found to be in good agreement with the simulated results. The performance of Gallium Nitride (GaN) based Junctionless (JNT) MOSFET at cryogenic temperatures has been presented and compared with conventional silicon and other compound semiconductor MOSFETs for channel length L = 18nm. Later the effect of temperature on the performance of GaN JNT has been studied. It is found that GaN based MOSFET shows higher drain currents, higher Ion/Ioff ratio and higher transconductance over other semiconductor materials. Also as the temperature increases the change in drain current and transconductance is minimum, so GaN based MOSFET is more immune to temperature variation.

Dual metal (DM) Insulated Shallow Extension (ISE) Gate All Around (GAA) MOSFET to reduce gate induced drain leakages (GIDL) for improved analog performance

In this paper a Dual Metal Insulated Shallow Extension Gate All Around (DMISEGAA) MOSFET has been proposed to solve a big issue of Gate Inducted Drain leakage (GIDL) current in cylindrical Gate All Around (GAA) MOSFET for improved analog performance. DMISEGAA MOSFET improves gate leakages by minimizing the tunneling from Valence Band to Conduction Band so bringing down the gate induced drain leakages. DMISEGAA MOSFET has been compared with cylindrical Dual Metal Gate All Around (DMGAA) MOSFET and cylindrical Gate All Around (GAA) MOSFET. DMISEGAA MOSFET exhibits higher drain currents, higher transconductance and higher output conductance. It also poses Subthreshold Slope (SS) in proximity with the ideal value and an enhanced on state to off state current ratio (Ion/Ioff ratio). Higher frequency operation of DMISEGAA MOSFET over DMGAA MOSFET and GAA MOSFET has been directed by higher cutoff frequency (fT) of DMISEGAA MOSFET.

AC analysis of Junctionless Double Surrounding Gate (JLDSG) MOSFET for Tera Hertz applications

In this paper, AC analysis of a novel Junctionless Double Surrounding Gate MOSFET for TeraHertz applications has been investigated and the results so obtained have been compared with the performance of Junctionless Transistor (JLT). AC performance parameters such as scattering parameters (S11, S12, S21, S22), cut off frequency, Gate Capacitance, Stern Stability Factor (K) and drain currents have been analyzed. The performance has also been analyzed for different channel lengths ( L= 18nm, 24nm, 30nm). JLDSG MOSFET is found to be suitable for Tera Hertz applications.

GaN based Junctionless Double Surrounding Gate (JLDSG) MOSFET for high power, high voltage and high frequency applications

In this paper GaN based JLDSG MOSFET has been analyzed for the time for different channel lengths (L = 18 nm, 24 nm, 30 nm) for its high power (HP), high voltage (HV) and high frequency operation. The performance of JLDSG MOSFET has been compared with conventional Junctionless Surrounding Gate (JLSG) MOSFET. It is found that JLDSG MOSFET poses high drain current, transconductance, Subthreshold Slope, Transconductance Generation Factor (TGF), cut off frequency (fT), Maximum Transducer Power Gain (MTPG) and Unilateral Power Gain (UPG).

An efficient high performance turbo code implementation in Rayleigh fading channel

Turbo codec in 3GPP LTE standard is implemented in an existing Rayleigh fading channel. Its bit error rate (BER) performance is gauged. The research is investigated to compare the performance of turbo codes with traditional Quadratic Permutation Polynomial (QPP) interleaver and comparatively simpler matrix interleaver in Rayleigh flat fading channel. The simulation outcome reveals that the BER performance of turbo codec with matrix interleaver outruns the performance with QPP interleaver.