DEVELOPMENT OF SIGNAL ENHANCEMENT TECHNIQUES FOR TARGET DETECTION WITH MICROWAVE/ MILLIMETER WAVE IMAGING SYSTEMS

Abstract

Signal and image processing are the classical tools to improve the detection ability of any imaging system, so signal enhancement is an integral part of any imaging technique to have a better signal to noise ratio (SNR). Different microwave and millimeter wave imaging techniques such as millimeter-wave radiometry, Infrared, Lidar, X-ray, and ultrasound sensors can be used to detect and locate the targets, but radar sensor is a more suitable ‘non-destructive technique’ (NDT) in many senses. The millimeter-wave radiometry technique can be harmful to the human body if exposed beyond a certain time. Infrared cannot be used to detect the target behind the wall at a larger distance due to higher attenuation from the wall. Ultrasound techniques can be used to detect and locate the target behind the metallic and non-metallic wall but cannot be used for imaging due to higher resolution requirements. Microwave/millimeter wave imaging is emerging as a popular technology because of the above reasons. It is useful in developing images for hidden objects which are not visible otherwise to the naked eye or by using high-definition cameras. These types of systems are very useful in several military, disaster management, civilian and industrial applications. The commonly used microwave/millimeter wave imaging systems are through-wall imaging (TWI), ground penetrating radar (GPR), and millimeter-wave imaging (MMW). Through-wall imaging is a popular technique to see ‘through the wall’, ground-penetrating radar to locate the target under the ground while to find out the objects under the ‘cloth’ or detect the cracks in the material millimeter-wave imaging can be useful. The major challenges faced by microwave/millimeter wave imaging are the noise and clutter due to the other reflections and objects present in the scene apart from the target. To overcome the above drawbacks, signal and image enhancement using signal processing techniques attracts the attention of many researchers with the objective of target detection and image resolution enhancement in microwave/ millimeter-wave imaging. The signal enhancement improves the system’s detection capability and image enhancement improves the image resolution.