Anil Vohra

Analysis of Sheet Electron Beam Transport Under Uniform Magnetic Field

The transport of sheet electron beam through the drift tube tunnel under uniform magnetic field has been analyzed. The edge curling due to the sharp increase of horizontal component of the space charge field has been explained by a windlike shear model, and an expression for vertical displacement of the beam edge from the top or bottom surface of the beam is derived on the basis of the aforementioned model. The effect of the height fill factor of the beam on the vertical displacement of the beam edge is analyzed analytically and then validated with numerical results by CST Particle Studio and OPERA 3-D software tools by considering some useful beam parameters. The vertical displacement of the beam edge enhances, and the higher portion of the beam is affected when it transports through short periodic vane-loaded interaction structures. For the sheet beam transport through planar vane-loaded structures suitable for subterahertz traveling-wave tube, the sum of the drift tube tunnel height and twice of the vane height should be considered as the effective tunnel height to calculate the required magnetic field in order to keep the vertical displacement maximum up to some desired value so that the beam edges must not strike on the vanes.

Sheet Electron-Beam Transport Analysis Through Closed Short PCM for Vacuum Subterahertz Devices

Closed short periodic cusped magnets consisting of miniature permanent magnets of material NdFeB 35H have been designed for transporting the sheet electron beam suitable for vacuum subterahertz devices. The aspect ratio of the magnetic tunnel is selected as 2 to provide proper focusing force in both horizontal and vertical directions. Numerical analysis performed by CST Particle Studio shows that both the peak value of the magnetic field and the nature of variation of the transverse components of the magnetic field along their respective transverse directions depend on the transverse thickness of the magnets. The peak value of the magnetic field increases by increasing the transverse thickness of the magnets. When the magnetic period, axial thickness, and transverse thickness of the magnets are 3.4, 1.3, and 8 mm, respectively, the simulated peak value of the magnetic field is 0.131 T. Under the tunnel of the aforementioned structure, the sheet electron beam of size 3 mm (width) × 0.15 mm (height), current density 100 A/cm2, and kinetic energy 20 keV transports up to a 60-mm distance without any significant instability through the drift tube of tunnel size 5 mm (width) × 0.3 mm (height). When the magnetic period, axial thickness, and transverse thickness of the magnets are 2.8, 1, and 8 mm, respectively, the simulated peak value of the magnetic field is 0.181 T. Under the tunnel of this structure, the sheet electron beam of size 2 mm (width) × 0.1 mm (height), current density 120 A/cm2 , and kinetic energy 20 keV transports up to a 60-mm distance without any significant instability through the drift tube of tunnel size 3 mm (width) × 0.2 mm (height).

A novel real-time resource efficient implementation of Sobel operator-based edge detection on FPGA

A new resource efficient FPGA-based hardware architecture for real-time edge detection using Sobel operator for video surveillance applications has been proposed. The choice of Sobel operator is due to its property to counteract the noise sensitivity of the simple gradient operator. FPGA is chosen for this implementation due to its flexibility to provide the possibility to perform algorithmic changes in later stage of the system development and its capability to provide real-time performance, hard to achieve with general purpose processor or digital signal processor, while limiting the extensive design work, time and cost required for application specific integrated circuit. The proposed architecture uses single processing element for both horizontal and vertical gradient computation for Sobel operator and utilised approximately 38% less FPGA resources as compared to standard Sobel edge detection architecture while maintaining real-time frame rates for high definition videos (1920 × 1080 image sizes). The complete system is implemented on Xilinx ML510 (Virtex-5 FX130T) FPGA board.

Staggered Closed PCM for Stable Rectangular Sheet Electron Beam Transport

Sheet electron beam transport under the magnetic field of a novel staggered closed periodic cusped magnet (PCM) has been investigated. In a staggered closed PCM, the horizontal and side magnets are placed in axially staggered positions and magnetized in the axial and transverse directions, respectively. Soft iron pole pieces are placed between two adjacent horizontal magnets of opposite polarity. Numerical analysis shows that effective root-mean-square value of the axial component of the magnetic field for the initial half cycle is higher for the proposed PCM than the conventional one by keeping the pole piece close to the magnets at first position. The magnetic period required to obtain desired peak value of the axial component of the magnetic field is shorter for the proposed PCM than for the conventional PCM for similar other parameters. Aforementioned advantages of the staggered closed PCM reduce the vertical displacement of the beam edge and stable transport of the sheet beam is possible through it. For a wide magnetic tunnel, required horizontal component of the magnetic field can be provided by extending the pole pieces between the horizontal magnets toward the beam surface and in the axial direction after the beam edges.

8-QAM Software Defined Radio Based Approach for Channel Encoding and Decoding Using Forward Error Correction

The aim of this paper is to use a software defined radio (SDR) based approach in order to select channel encoding and decoding method accordingly using 8-QAM (Quadrature Amplitude Modulation) in terms of bit error rate (BER). By selecting a higher order format of QAM, we are able to carry more bits of information per symbol; also the data rate can be increased thus achieving greater distance between adjacent points in the I–Q plane by distributing the points more evenly. Hence the constellation points are more distinct and data errors are reduced. In the present work 8-QAM is chosen as modulation scheme so that balance can be maintained between higher data rates while maintaining an acceptable bit error rate for SDR. Channel coding schemes forward error correction are used where the re-transmission of the data is not feasible, thus redundant bits are added along with the message bits and transmitted through the channel. On the receiver side, this channel coded signal is decoded in order to get back the original data even if the channel coded signal undergoes some interference from the noise in the transmission medium. The performance is then analyzed in terms of BER for Hamming and convolution coding algorithms at a particular value of SNR in LabVIEW graphical programming. With the help of LabVIEW we were able to design the systems in a block-based manner in shorter time as compared to the commonly used text-based programming languages.

Comprehensive Review and Comparative Analysis of Hardware Architectures for Sobel Edge Detector

This paper presents a comprehensive review and a comparative study of various hardware/FPGA implementations of Sobel edge detector and explored different architectures for Sobel gradient computation unit in order to show the various trade-offs involved in choosing one over another. The different architectures using pipelining and/or parallelism (key methodologies for improving the performance/frame rates) are explored for gradient computation unit in Sobel edge detector. How the different architectures affected performance (in terms of video frame rate and image size) and area (in terms of FPGA resources usages) has been demonstrated. By exploiting the trade-offs between video frame rate, image size, and FPGA resources a designer should be able to find an optimal architecture for a given application.

Electrical Properties of Electrodeposited ZnCuTe Ternary Nanowires Embedded in Polycarbonate Membrane

The electrical properties of electrodeposited zinc-copper-telluride (ZnCuTe) nanowires embedded in polycarbonate track-etch membrane (Whatman) having pore-diameters of 200, 100 and 50nm have been studied and reported in this paper. Scanning electron microscopy (SEM) confirmed the formation of the nanowires of uniform diameter equal to the diameter of the templates used. I-V measurements at room temperature (303K) reveal that the nanowires of diameter 200, 100 and 50nm have linear and ohmic characteristics. Higher electron transport was observed in larger diameter nanowires compared to smaller ones which may be attributing to size effect. The temperature-dependent electrical transport measurements over a temperature range 308- 423K reveal that the temperature dependence of electrical conductivity increases with increasing temperature and decreases as the nanowires size decreases. The study reveals that ZnCuTe nanowires have negative temperature coefficient of resistance (TCR).

Novel Design of a Low Cost Flexible Transceiver Based on Multistate Digitally Modulated Signals Using Wi-Fi Protocol for Software Defined Radio

This paper relates to development of a novel generic transceiver module for software defined radio (SDR) built using graphical user interface language LabVIEW. The main advantage of the module is that it is built entirely on the user input interface where the users get the flexibility to change any parameters according to their needs and the generic module supports there digital modulation schemes with two forward error correction coding techniques where the user has the flexibility to decide about the same. The SDR module has been fully implemented and it has the ability to navigate over a wide range of frequencies with programmable channel bandwidth and modulation characteristics. The module has been tested on real time data, text and image transmissions using the test jig for Wi-Fi module. With the help of the Wi-Fi hardware test jig it has been proved that the signal transmitted has been recovered with very low probability of error at the destination. A plot between bit error rate (BER) and the signal to noise ratio shows that a low BER has been achieved using this design. The novelty of this design is that the module auto identifies the best available digital multistate modulation scheme i.e. M-ary quadrature amplitude modulation, M-ary frequency-shift keying, M-ary phase-shift keying for the selected input.

Pole-Piece With Stepped Hole for Stable Sheet Electron Beam Transport Under Uniform Magnetic Field

An electron gun is designed for a W-band sheet beam TWT using a planar rectangular cathode working in the space charge limited region. A permanent magnet solenoid focusing system is designed to focus the beam. A pole-piece with a novel multisized (stepped) hole is investigated for stable transport of the beam. The size of the hole in the pole-piece is larger near to the magnets and it is gradually decreased stepwise toward the cathode. The pole-piece with the multisized hole reduces both the transverse magnetic field and magnitude of flux leakage toward the cathode. Simulation results show that the sheet beam transports without significant beam ripple and edge curling under the magnetic field of the designed focusing structure with the pole-piece of multisized hole. The thermal velocity of the electrons is also considered in the simulation. The beam transmission up to 70-mm distance is 98.8% and 97.3%, respectively, for nonthermal and thermal beam under the magnetic field of the designed focusing system.

Real-Time Implementation of Change Detection for Automated Video Surveillance System

Change detection is one of the several important problems in the design of any automated video surveillance system. Appropriate selection of frames of significant changes can minimize the communication and processing overheads for such systems. This research presents the design of a VLSI architecture for change detection in a video sequence and its implementation on Virtex-IIPro FPGA platform. Clustering-based scheme is used for change detection. The proposed system is designed to meet the real-time requirements of video surveillance applications. It robustly detects the changes in a video stream in real time at 25 frames per second (fps) in gray scale CIF size video.