K. Raja Rajeswari

RP-HPLC method for the simultaneous determination of Atorvastatin and Amlodipine in tablet dosage form

A simple, precise, accurate, and rapid HPLC method has been developed, and validated for the determination of atorvastatin and amlodipine simultaneously, in combined tablet dosage form. The mobile phase used was a mixture of acetonitrile and 0.03M phosphate buffer pH 2.9 (55:45% v/v). The detection of atorvastatin and amlodipine was carried out on dual g absorbance detector at 240 nm and 362 nm, respectively. Results of the analysis were validated statistically, and by recovery studies. The proposed method can be successfully used to determine the drug contents of marketed formulation.

Unscented Kalman Filter with Application to Bearings- Only Target Tracking

Abstract The unscented transformation coupled with certain parts of the classic Kalman Alter, provides a more accurate method than the Extended Kalman Filter for nonlinear state estimation. Using bearings-only measurements, the unscented Kalman Filter algorithm estimates target motion parameters and detects target maneuver, using zero mean chi-square distributed random sequence residuals, in a sliding window format. During target maneuvering, the co-variance of the process noise is sufficiently increased in such a way that the disturbance in the solution is minimized. When target maneuver is completed, the covariance of process noise is lowered. The performance of this algorithm is evaluated using Monte Carlo simulation and results are presented.

Four-phase orthogonal code design for MIMO radar systems

MIMO (Multiple-Input Multiple-Output) Radars have received considerable attention over the last decade due to their enhanced performance potential. Unlike phased array radar, MIMO radar transmits orthogonal waveforms via its transmitting antennas to improve separability of individual returns at the receiver elements. In this paper, an alternate method for generating four-phase sequences with good autocorrelation and cross correlation properties is proposed. The advantages of the proposed scheme include constant envelope, finite alphabet, large family and efficient structure for generation.

A Genetic Algorithm Based Oblivious Image Watermarking Scheme Using Singular Value Decomposition (SVD)

Digital Watermarking and data hiding have gained popularity in recent years as a means of protecting digital images from theft, illegal copying and unlawful reproduction. Some digital watermarking algorithms were proposed using spatial domain and transform domain techniques. The transform domain could be DFT, DCT, DWT or SVD. Several digital watermarking algorithms using Genetic Algorithms are available in the literature. In this paper, a novel optimal watermarking scheme based on Singular Value Decomposition using Genetic Algorithm (GA) is proposed. The proposed scheme is based on step size optimization using the genetic algorithm to improve the quality of watermarked image and robustness of the watermark. The proposed algorithm is more secure and robust to various attacks, viz., Low Pass Filtering, Median Filtering, JPEG Compression, Resizing, Row-Column blanking, Row-Column Copying etc. Superior experimental results were observed with the proposed scheme over a recent algorithm proposed by Chandra Mohan et al. in terms of Normalized Cross correlation(NC) and Peak Signal to Noise Ratio(PSNR).

New Figures of Merit for Pulse Compression Sequences

Two usual criteria of goodness of pulse compression sequences are discrimination and merit factor. Here new measures of goodness called ‘figures of merit’ are proposed. Justification for them is offered in terms of the properties the measures of goodness should have and the notions analogous to robust signal processing. The return signal is assigned to equivalence classes based on the notion of Hamming distance and the proposed figures of merit are defined in terms of appropriate crosscorrelation properties averaged over the neighbourhood of the transmitted sequence. These figures of merit are tabulated for some binary and ternary sequences. They indicate how the performance of a pulse compression sequence deteriorates as the medium gets noisier and bring out that the best sequence may be different at different noise levels. Adaptive, diversity-combinatorial and robust schemes of pulse compression arise as a result.

MIMO radar ambiguity analysis of frequency hopping pulse waveforms

Radar systems employing multiple transmit antennas and multiple receive antennas have received great interest over the last decade. While single-input multiple-output (SIMO) radar systems employ only spatial diversity, multiple-input multiple-output (MIMO) radars employ both spatial and waveform diversity to improve the system performance. Waveform design for MIMO radars involves optimization of desired delay, Doppler and spatial resolution characteristics. Designs of frequency hopping waveforms that optimize the MIMO radar ambiguity function under small and large Doppler scenarios were recently proposed. These waveforms are obtained by optimizing an appropriately formulated cost function using modified simulated annealing algorithms. In this paper, the MIMO radar ambiguity properties of large sets of frequency hopping waveforms based on algebraic theory are analyzed and their relative performance are compared.

MIMO radar ambiguity analysis of phase coded pulse waveforms

Multiple Input Multiple Output (MIMO) radars transmit partially coherent or noncoherent waveforms for improving spatial resolution or spatial diversity. While waveform design for SIMO radars concentrate on improving the delay and Doppler resolution characteristics, waveform design for MIMO radars involve optimization of delay, Doppler and spatial resolution characteristics. MIMO radar ambiguity function of frequency hopping waveforms is recently derived. In this paper, MIMO radar ambiguity function of phased coded pulse waveforms is derived. Polyphase pulse waveforms based on Kumar sequences are analyzed using this derived MIMO ambiguity function through simulations.

Performance Comparison of Wiener Filter and CLS Filter on 2D Signals

Images acquired by optical, electro optical or electronic means are likely to be degraded by the sensing environment. The degradations may be in the form of sensor noise, blur due to camera misfocus, relative camera motion, random atmospheric turbulence, and so on. Image restoration is concerned with filtering the observed image to minimize the effect of degradation. The effectiveness of image restoration filters depends on the extent and accuracy of the knowledge of the degradation process as well as on the filter design criterion. In this paper, we have considered the performance of Wiener and (CLS) constrained least square filtering methods on the basis of noise to signal ratios, image power, noise power and histograms on restoration images.

Time-delay estimation using MLE approach for wide-band radar systems

The problem of time-delay estimation has considerable practical importance in the area of communication. Consequently many procedures have been developed for this estimation. One such is the maximum likelihood estimation (MLE) method where the time delay between the signals received at two spatially separated sensors in the presence of uncorrelated noise can easily be estimated. A cross-correlation of the resulting sequences is carried out to determine the time difference of arrival (TDOA) of the signal at the two sensors. This can be realized in practice by a pair of receiver filters followed by a cross-correlator. Also the true parameters of interest and hence the target location can be obtained from a set of time delay measurements using a group of sensors.

A New Approach to Investigation of Discrete Wavelet-Based Multiuser MIMO-OFDM for BPSK Modulation Scheme

This paper investigates the approach of discrete wavelet to multiuser (MU) MIMO-OFDM systems and further makes a comparison with the conventional Fast Fourier Transform (FFT) founded MU-MIMO-OFDM. Discrete wavelet-based system is found superior in performance over the FFT based one, where the requirement of cyclic prefix has been eliminated making flexible with greatest selection. The concept of discrete wavelets is a best fit in all the areas of Wi-Fi verbal schemes with OFDM, which is an enduring application for subsequent users. Simulations were created for the double multicarrier schemes. Haar wavelet has been utilized in this paper since it shaded out the performance of its counterparts like Daubechies and Symlet. The proposed wavelet-based scheme superseded the conventional-based system in terms of Bit Error Rate (BER) taking a couple of antennas by means of BPSK and QPSK as dual modulation schemes over the Additive White Gaussian Noise (AWGN) Channel.