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Vol 45, No 3, July-September 2004
Band-pass/Band-stop Filter Design by
Frequency Transformation
S C DUTTA ROY, DFIETE
Given the specifications of a band-pass filter (BPF) or a band-stop filter (BSF), the same can be translated to those of a normalized low-pass filter (LPF) by frequency transformation. Once the latter is designed, one can realize the BPF/BSF by using the same transformation in the reverse manner. The process of translation to the normalized LPF is usually not explained in details in standard text-books, and in some of them, the process has even been wrongly stated or illustrated. This paper clarifies this important step in BPF/BSF design.
Design of a Broadband Two Layered Slotted Rectagular
Microstrip Antenna with a Single Feed
P K SINGHAL, FIETE, BHAWANA DHANIRAM AND ASHIMA KHERA
Microstrip Patch Antennas (MPA) are very useful for high frequency range due to their small size and low cost. However, they have their greatest limitation in terms of small bandwidth. To enhance the operational bandwidth and make it more effective, parasitic patch, slots and cavity walls have been used. This paper presents a broadband double-layered slotted rectangular microstrip patch antenna of bandwidth 40%. Use of metallic walls enhances it to 62.94% for VSWR <2.00. Proposed antenna has been simulated using IE3D software. Various antenna parameters have been examined with and without using the metallic walls.
An Algorithm for Task Scheduling in
Heterogeneous Computing Environment
G GABRANI, FIETE, AND ABHISHEK KHARE
Heterogeneous computing systems are of considerable interest because a single parallel architecture may not be adequate for exploiting all the parallelism available in the program. In some cases, heterogeneous systems perform better than a single large machine and that too at a lower cost. In heterogeneous systemms, task scheduling is done with a view to minimize the overall completion time of a parallel application by properly allocating the tasks to the processors. In this paper, a task-scheduling algorithm called Alternate Heterogeneous Earliest Finish Time (AHEFT) is proposed and its performance is analyzed with respect to Heterogeneous Earliest Finish Time (HEFT) algorithm. A simulation environment has been developed in C++ and both the algorithms were implemented. Different weighted Directed Acyclic Graphs (DAG's) were used to compare the two algorithms. A network of fully connected heterogeneous processors was assumed for task scheduling. The performance indices used for comparison of algorithms are Schedule Length, Speedup Factor and Efficiency. The results substantiate the fact that for higher values of CCR (Communication to Computation Ratio), AHEFT algorithm performs better than HEFT. Moreover, as the number of tasks in the DAG increase, the performance improvement of AHEFT algorithms is more as compared to HEFT.
Vol 45, No 4, November - December 2004
Information Theory and
its Two basic Applications
R C Jain, miete
Entropy, relative entropy and
mutual information which are three fundamental quantities in information theory
are discussed. The difference between entropy of an information source and
thermodynamic entropy is given. The meaning of the term information source is
discussed in detail. Two applications of information theory: data compression
and data transmission are given. Entropy also gives the lower limit up to which
lossless compression can be achieved. When rate of transmission is less than or
equal to the capacity of the channel, reliable communication can be obtained on
a noisy channel. The theoretical limits given by information theory motivate
researchers to find new practical systems to reach closer to these limits.
Derivation of the FIR Lattice Structure
S C Dutta Roy, Dfiete, and R Vishwanath
A simple derivation is presented for the FIR lattice structure, based on the
digital two-pair concept.
Simulation of Slotted, Controlled and Heirarchical Alohas
Sudhanshu gupta and H M Gupta
In this paper a simulation tool is
presented for characterization of Slotted and Controlled Alohas. The tool will
be useful in obtaining throughput versus load, delay versus throughput and
backlog versus throughput characteristics. A new scheme, Hierarchical Aloha is
proposed and its performance is found to be superior to the Slotted Aloha.
Matlab Simulation of a Fuzzy Controller for Attitude Control of a Geostationary Satellite
S B Pokle, K D Kulat, fiete, and A G
Keskar, fiete
The Geostationary satellite undergoes drift in its position due to variety of
forces acting on it. These forces are additive in nature. Since satellite
communication is highly line of sight communication, attitude (drift in its
position) has to be controlled. For this it is necessary to determine the exact
position of the satellite from time to time. Once the satellite position is
determined, appropriate correction can be applied by suitable attitude control
system. Various techniques exist for attitude control of a satellite.
Conventional techniques like proportional, Bang-Bang controllers etc are in use.
New research work in fuzzy theory shows that fuzzy controllers can provide
faster control over traditional ones. In this paper, fuzzy controller is
designed using MATLAB. Simulink model interfaced with MATLAB shows relatively
much better results over traditional controllers for on board simulation.
New Nonlinear
Filtering Strategies for Eliminating Medium and Long Tailed Noise in Images with
Edge Preservation Properties
E Srinivasan
Arithmetic filters are quite effective in recovering the images confounded by medium-tailed (Gaussian) noise. These filters, however, perform poorly in the presence of additive long-tailed (impulse) noise and they do not preserve edge structures. Median smoother discards outliers (impulses) effectively, but it fails to provide adequate smoothing for images corrupted with non-impulsive noise. In this paper, two new nonlinear techniques for image filtering, which we call New Filter I and New Filter II, are proposed based on a recently developed nonlinear highpass filter algorithm. New Filter I suppresses Gaussian noise quite well. New Filter II effectively eliminates impulses and filters out noise having Gaussian statistics. Both the filters are shown to have good edge preserving characteristics. The proposed filters are evaluated for their performance on a test image and the results obtained are included.
Application
of Information Theory to Spectral Estimation
R C Jain
The need for spectral estimation in some areas of science and engineering is discussed. Some early developments in this area, with an emphasis on the problems in different methods of spectrum estimation are briefly described. Parametric and non-parametric methods are briefly discussed. The maximum entropy method which provides an unbiased method to select unknown data values, that are not determined by the prior information, is given at the end.
Development of Active Bridge Technique for Measuring Low Capacitance Over Wide Frequency Range
Tarikul Islam and H Saha
BJT Biasing Revisited
S C Dutta Roy
The familiar four resistor circuit for biasing a Bipolar Junction Transistor (BJT) is generalised through simple reasoning, and transformed to yield a different topology. Three alternative four resistor circuits are derived as special cases of the transformed generalised circuit, which do not appear to have been widely known in the literature. A detailed and careful analysis reveals that the bias stability parameters of all the alternative circuits are comparable to those of the conventional circuit. An illustrative example is included for demonstrating this fact.
Determination of Amplitudes of the Frequency Components present in a Single Tone Amplitude Modulated Carrier through Lissajous Figures
P Hari Krishna Prasad, FIETE
This paper presents a technique for determining the amplitudes of the frequency components present in a single tone amptitude modulated sinusoidal carrier wave through the use of Lissajous figures. The amplitude modulated signal and the reference sine wave are applied to the deflection plates of cathode ray oscilloscope(CRO), which is being operated in X-Y mode. Appropriate selection of the reference signal amplitude based on a certain criterion used in conjunction with the Lissajous figure will enable the determination of the amplitudes of the side frequency components. The mathematical equations, experimental results along with the limitations of this method are presented.
A Note on the FFT
S C Dutta Roy, DFIETE, D Mohan Krishna and Nilotpal Ghosh
This note gives a formula for the exact number of non-trival
multipliers required in the basic N-point FFT algorithms, where N is an integral
power of 2.
Vol 46, No 3, July-September 2005
Basic
Principle of Beam forming using Array Antenna
Mainak Mukhopadhyay, amiete, and Ajay
Chakrabarty
Basic principle of Beam forming in
Adaptive Array Antenna with analogy with the FIR
filter structure antenna and adaptive controlling of radiation pattern through
weighting vector is presented.
Multiple
Watermarking Scheme for Digital Images
M S Raval & P P Rege,
If
you hold any currency note up to the light you will see the portrait echoed in
the note in form of watermark. It makes the currency note difficult to fake.
Similarly the boom of internet which has acted as a distribution system for
digital media, content owner sees the risk of piracy. Invisible watermarking
involves imperceptibly embedding data called as “Watermark” into an image or
other digital media to protect its value. Different techniques are used to embed
different types of watermark to accomplish various goals. Some are intended to
robustly carry ownership information, some are intended to carry content
verification information like in medical imaging. These two are extremely
diverse requirements. In this work, to accomplish several goals we propose to
embed multiple watermarks in a cover image. A robust watermark is embedded to
convey the ownership information. For it to be effective, it should robustly
resist image processing attacks, intentional or unintentional, that might remove
it. For the application of content authentication of image we focus on how the
watermark can be used to assist in verifying the integrity of the associated
cover image. We call this watermark a “Fragile Water mark” as it is
extremely sensitive to any intentional or unintentional change.