Analysis and Modeling of Probe-Fed Rectangular DRA Using Artificial Neural Network

-- Sriparna Bhattacharya (Mitra) and Bhaskar Gupta

Dielectric Resonator Antenna (DRA) has become very popular in the field of wireless communication and a lot of research has been done in this field in the last few decades. But no closed form relationship is still available relating the dimensions of the DRA or those of feed structures to the performance parameters of the antenna. Various models and numerical techniques are used to predict the performance parameters of the antenna. The disadvantages are that the first approach gives only approximate values and the second one is a time-consuming process. On the other hand, Artificial Neural Network (ANN) is a mathematical model which is used to predict the performance parameters of any complex nonlinear system. Once the model is ready, the ANN predicts very quickly the performance parameters for a given set of input parameters. So two ANN models are developed for DRAs operating at two different center frequencies of the ISM bands. The ISM bands with center frequency of 2.45 GHz (2.4-2.5 GHz) and 5.8 GHz (5.725-5.875 GHz) are chosen as both of them have widespread application, and considering their importance, the DRAs are separately made to operate in these two bands. Both the models are first trained using two different datasets collected through simulations using the software ANSYS HFSSTM (v.13). The outputs of the ANN models are then compared with other two test datasets, and in every case, the error found is negligibly small. The outputs of the neural networks are also verified experimentally. Each of the networks is trained with five input parameters, the three dimensions of the rectangular DRA (length, width and height) along three axes, probe offset position and the probe height. The output parameters consist of resonant frequency, gain and bandwidth.

© 2014 IUP. All Rights Reserved.

Modeling of Subthreshold Surface Potential for Short Channel Double Gate Dual Material Double Halo MOSFET

--Debarati Das, Swapnadip De , Manash Chanda and Chandan Kumar Sarkar

The short channel effects can be reduced using two techniques—the gate engineering technique and the channel engineering technique. The gate material engineering technique allows the Double Material Gate (DMG) devices to have same threshold voltage for a reduced doping concentration in the channel region, which gives better immunity to mobility degradation. In DMG MOSFET, two different materials of different work functions are combined to form a single gate of a bulk MOSFET, and in the channel engineering technique, a single halo or double haloes are used, which shows a considerable reduction of Strongly Correlated Electron Systems (SCEs) and hot electron effects. It is seen that a single gate double material double halo MOSFET provides excellent short channel suppression as compared to single halo or double halo MOSFET for channel lengths around 40 nm. In this paper, a surface potential model for Double Gate Double Metal Double Halo (DGDMDH) MOSFET in the subthreshold regime is proposed. The basic idea is to model the subthreshold surface potential applying Gauss’s law to a rectangular box covering the depletion layer depth. This structure provides excellent immunity to short channel effects as compared to conventional devices and hence can be used in low power VLSI circuits.

© 2014 IUP. All Rights Reserved.

Spwm Techniques in Closed Loop Control of Five-Level Inverter Fed 3F Induction Motor

-- M V Subramanyam and P V N Prasad

The paper investigates the effect of carrier frequency variation on Total Harmonic Distortion (THD) of output current using different Sinusoidal Pulse Width Modulation (SPWM) techniques. The induction motor is fed by closed loop fuzzy logic controlled five-level Multilevel Inverter (MLI). The MLI has several advantages over two-level conventional inverters such as reduced harmonics and lower voltage stress on power electronic switches. The different techniques in SPWM of phase disposition methods are used.

© 2014 IUP. All Rights Reserved.

Ultrathin Narrowband Convoluted Square Frequency Selective Surface-Based Microwave Absorber

--Deepak Sood and C C Tripathi

In this paper, the design, fabrication and experimental characterization of a ultrathin, polarization insensitive, planar microwave absorber are presented. The unit cell of the absorber consists of convoluted square as Frequency Selective Surface (FSS) within a metal grid. The designed absorber results in efficient absorption of the incident microwave energy. The validation of the proposed design is conducted by fabricating a 1.63 mm thin (only 0.054l) absorbing array of 15 ´19 FSS elements which is then tested for normal and oblique incidences through horn antenna on low cost X-band microwave test bench setup using WR90 waveguide. Full wave electromagnetic simulation demonstrates 99.999% microwave absorption at 10.7 GHz with 1.86% absorption bandwidth. The absorber demonstrates very good absorption rate and frequency stability for Transverse Electric (TE) and Transverse Magnetic (TM) polarizations with variation in incidence angle (q) from 0° to 45°. The parametric analysis of the proposed FSS-based absorber is carried out to understand its absorption mechanism for practical applications.

© 2014 IUP. All Rights Reserved.

Two-Unit PLC System with Preventive/Corrective Maintenance and Repair

--Manoj Duhan and Anil Dahiya

The paper deals with two-unit cold standby Programmable Logic Controller (PLC) system with regular inspections, repairs and various types of maintenances by regular visiting repairmen at industry itself or at service station. From the literature, it is observed that in the past, considerations were depicted regarding the hypothetical industrial cases. It is felt that a practical industrial case may be taken up, in which practical side of the unit will be studied with utmost care and slightness. For this purpose, we have taken PLC as a unit. Here regular engineers are appointed; expert repairman can also be called upon, if required. Besides, PLC can be sent to authorized service station if required. To go deep into the matter, two types of maintenances—preventive and corrective maintenance—can be consulted. Also, various reliability parameters of a system are studied and plotted graphically.

© 2014 IUP. All Rights Reserved.