TIME FREQUENCY ANALYSIS - AN APPLICATION TO FMCW RADARS

The Fourier transform of a signal defines the frequency domain representation of the signal in that it specifies relative amplitudes of the various frequency components of the signal. However, the Fourier transform is not always the best tool to analyze 'real-time signals' which have frequency components that change over time. Joint time-frequency techniques were developed for characterizing the time-varying frequency content of the signal. This project presents an overview of the basic concepts and well-tested algorithms for joint time-frequency analysis with particular reference to their application to radar signals. The time-frequency techniques can be classified into twofrequency distribution series). The aforementioned techniques are discussed in detail and are tested first against ideal simulations of normal cosine and chirp signals and then with the radar beat signal. A brief description of FMCW sea-ice radar developed in RSL, University of Kansas is given, and the data from this radar is used as experimental data to compare simulation results with measured sea-ice thickness levels. One of the important applications of time-frequency analysis is to exactly predict the occurrence of surface return layers and to distinguish it from noise signals and multiples. These techniques are also investigated for time-variant filtering of noise from the radar echogram and suitable recommendations are provided. iii To my parents & brother iv ACKNOWLEDGEMENTS I would like to thank Dr. Glenn Prescott (Advisor & Chair) for giving me the opportunity to work on this research project. He has been a great source of inspiration and his invaluable guidance and timely input has helped me throughout my Masters degree course in the University of Kansas. I would also like to thank Dr. Christopher Allen for serving on my project committee and for giving me the opportunity to work as Graduate Teaching assistant under his supervision. His guidance has given me an exposure to interact with people, lead a team of students as well as learn new things. I also thank Prof. Swapan Chakrabarti for serving on my committee. A special mention to Dr. Pannirselvam Kanagaratnam for helping me in providing the radar testing data, for numerous simulation related discussions that I have had with him, for showing constant interest and enthusiasm in my work and helping me to complete the project successfully. Special thanks to my friend Sudarsan Krishnan, who has been instrumental in motivating my approach, guiding me in each stage of project and helping me in times of …