Preprocessing for Extracting Signal Buried

Abstract

Digital signals are used everywhere in the world around us due to its superior fidelity, noise reduction, and signal processing flexibility to remove noise and extract useful information. This unwanted electrical or electromechanical energy that distort the signal quality is known as noise, it can block, distort change or interfere with the meaning of a message in both human and electronic communication. Engineers are constantly striving to develop better ways to deal with noise disturbances as it leads to loss of useful information. The traditional method has been used to minimize the signal bandwidth to the greatest possible extent. However reducing the bandwidth limits the maximum speed of the data than can be delivered. Another, more recently developed scheme for minimizing the effect of noise is called digital signal processing. Digital filters are very much more versatile in their ability to process signals in a variety of ways and can handle low frequency signals accurately; this includes the ability of some types of digital filter to adapt to changes in the characteristics of the signal. Fast DSP processors can handle complex combinations of filters in parallel or cascade (series), making the hardware requirements relatively simple and compact in comparison with the equivalent analog circuitry. In order to extract useful information from the noisy signals, raw signal has to be processed. By analyzing and processing the digital data, the useful information is obtained from the noise and present it in a form more comprehensible than the raw data. The signal processing can be roughly divided into two stages by functionality: preprocessing and feature extraction. The preprocessing stage removes or suppresses noise from the raw signal and the feature extraction stage extracts information from the signal. In this thesis the extraction of a signal i.e. preprocessing is done by using LabVIEW which has extensive set of signal processing VI’s that simplify the development of digital processing system for improved noise reduction and efficient extraction of desired signal.