Informatics Publishing Limited

M. V. Nageswara Rao ¹, K. Raja Rajeswari ²

Affiliations
1 Department of ECE, G. M. R. Institute of Technology, Rajam, Srikakulam (D.T), A.P, IN
2 Department of ECE, College of Engineering, Andhra University, Visakhapatnam, A.P, IN

Abstract

Ternary codes have been widely used in many applications such as in synchronization of block codes and pulse compression codes in radar. When these codes are used for radar applications, the auto correlation property must be good, but the design of ternary sequences with good auto-correlation property is a nonlinear multivariable optimization problem, which is usually difficult to deal with. This paper presents a novel and efficient design of Ternary sequences with low Peak Sidelobe Ratio (PSLR) using Particle Swarm Optimization with Cauchy Mutation (PSOCM) technique. The various properties of these sequences like autocorrelation function, peak sidelobe ratio have been studied. The performance of these sequences in detection, and range and Doppler measurement is also demonstrated. The cross-ambiguity function(CAF) method is used to detect the stationary and moving targets in various target detection scenarios. The contour plots of the crossambiguity function are computed as a function of delay and Doppler frequency shift. The results of ternary sequences of the sequence
lengths N=30, N=100, N=200, N=500 and N=1000 are compared.

Keywords

Cross Ambiguity Function, Cauchy Mutation, Particle Swarm Optimisation, Ternary Sequences.

Full Text

     

B. Leelaram Prakash ¹, K. Raja Rajeswari ²

Affiliations
1 Vignnan's Institute of Information Technology, Visakhapatnam, IN
2 A.U. College of Engineering (A), Visakhapatnam, IN

Abstract

Pulse compression achieved with un-weighted linear FM (LFM) suffers from relatively high autocorrelation function (ACF) side-lobes. Since the ACF is the inverse Fourier transform of the power spectrum, the ACF sidelobes could be reduced by shaping the signal according to one of the many sidelobe suppression techniques. The shaping is performed by changing the pulse amplitude along the time axis. In LFM instantaneous frequency is linearly related to time. Indeed, the resulting spectral shaping is very close to the desired spectrum. But it has a serious drawback. In a matched transmitter-receiver pair, it results in variable amplitude of the pulse transmitted. Variable amplitude requires linear power amplifiers which are less efficient than saturated power amplifiers. This problem can be alleviated by performing amplitude weighting only at the receiver. The resulting mismatch causes SNR loss. In linear FM the transmitter spends equal time at each frequency; hence the nearly uniform spectrum will result. Another method for shaping the spectrum is to deviate from the constant rate of frequency change and to spend more time at frequencies that need to be enhanced. This approach is termed as nonlinear FM (NLFM). In this paper an attempt is made to compare the performance of Gaussian NLFM, Rayleigh NLFM and the combination of both these NLFM signals with respect to their ambiguity plots and range resolution plots.

Keywords

Pulse Compression, LFM, NLFM, Ambiguity Plot and Range Resolution Plot.

Full Text

     

Ch. Srinivasu ¹, K. Raja Rajeswari ¹

Affiliations
1 Department of ECE, AUCE (A), Visakhapatnam, IN

Abstract

The performance of ultra wideband (UWB) radar in target detection, resolution and recognition depends on the structure of the radar waveform. So, many types of waveforms are being used in multi target detection in the field of radar. Sinusoidal and non-sinusoidal waveforms can be implemented practically. In this paper performance of non-sinusoidal waveforms are presented. Resolution is the important parameter, which gives the goodness of the waveform.  The ambiguity function is a three dimensional and two variable mathematical tool, which demonstrates the both range and Doppler resolution capability of the waveform. These two resolutions are important parameters to know the goodness of the transmitted waveform. In practical applications of the radar these parameters are essential to resolve the closely moving (or stationary) targets in the space. In this paper mathematical models of ambiguity functions are developed for bi-phase coded non-sinusoidal UWB Gaussian waveforms signal. Ambiguity plots are three dimensional plots, which represent range axis, Doppler axis and magnitude axis. The three dimensional plots are generated for the above UWB coded signals and results are compared with sinusoidal coded waveforms.

Keywords

Ambiguity Function, Barker Codes, Range Resolution.

Full Text

     

B. L. Prakash ¹, G. Sajitha ², K. Raja Rajeswari ³

Affiliations
1 Department of Electronics and Communication Engineering, K.L. University, Guntur - 522502, Andhra Pradesh, IN
2 Department of Electronics and Communication Engineering, K.L. University, Guntur - 522502, Andhra Pradesh
3 Viswanadha Institute of Technology and Management, Visakhapatnam - 531173, Andhra Pradesh, IN

Abstract

Background/Objectives: In modern radars waveform design plays a vital role. In the design of radars the most significant parameter is the range resolution. With the help of the signal processing tools like auto correlation and ambiguity function various waveform designs can be achieved. Methods/Statistical Analysis: In the proposed paper the discrete frequency coding method of random NLFM (Non Linear Frequency Modulation) signal is described which results in a random like frequency evolution. Random NLFM enables to achieve the thumbtack ambiguity function while minimizing the crosstalk between frequencies. Findings: Random NLFM signals for different lengths are generated which are used in radars and sonars and also their ambiguity plots are obtained. The PSLR (Peak Side Lobe Ratio) and ISLR (Integrated Side Lobe Ratio) for these signals are evaluated and a comparison is made among these signals to identify best NLFM waveform. Application/Improvements: Non Linear Frequency Modulation waveforms using algebraic random number generators that are quite robust to electronic counter measures and have long duration for long range applications. In future applications of NLFM especially in RADAR/SONAR applications, this idea may result into new methodology

Keywords

Ambiguity Function, Discrete Frequency Coding, ISLR, NLFM, PSLR, Pulse Compression, Radar.

Full Text

   

K. Raja Rajeswari ¹, C. H. Sri Durga ¹, V. Rama Mohan Gupta ¹

Affiliations
1 Pulla Reddy Institute of Pharmacy, Affiliated to Jawaharlal Nehru Technological University, Hyderabad, Telangana-502 313, IN

Abstract

Apart from the regular clinical trials, bioavailability/bioequivalence studies are conducted to assess the safety and efficacy of generic drugs, comparing it with a reference listed drug. Clinical trial data is mandatory for further approval of the drug, for it to enter the market. These investigations are strictly regulated by various global and national regulatory authorities. The global clinical trials market is expected to register a Compound Annual Growth Rate (CAGR) of nearly 4.5% during the forecast period, 2018 to 2023. A major challenge for them to achieve the forecasted growth is meeting the increased level of compliance to the regulations. In recent times the research Organizations have been issued an increased number of warning letters with stringent procedures and even subsequent closure of the organizations. This case study conducted by the review of warning letters and other observations pointed out by two major global regulatory authorities, the FDA and EMA and the critical areas were identified. Recommendations were made for the major areas which were critical and repetitive. It was concluded that consistent methods are required to improve the quality of studies to effectively eliminate the challenges in mere future and contribute for the betterment of the drugs’ market.

Keywords

World Health Organization, Food and Drug Administration, Clinical Research Organizations, Quality Management System, Clinical Trials, Regulatory Authorities, Warning Letters, Medical Devices, Drugs, Biomedical Research.

Full Text