High Resolution Radar Focusing Using Spectral Estimation Methods in Wide-Band and Near-Field Configurations: Application to Millimeter-Wave Near-Range Imaging

Abstract

The spatial resolution of an imaging system is a key factor, which steers its performance for complex target detection, characterization and recognition. Active electromagnetic imaging systems with limited frequency bandwidth and synthetic aperture may fail to discriminate important details during the imaging process, due to their insufficient resolution properties. Spectral estimation methods may be used to overcome such limitations through dedicated signal processing techniques. This study proposes a new signal processing chain, which is able to cope with near-field and wide-band configurations, to significantly improve 2-D resolution, using classical spectral estimation methods. This work is based on the efficient handling and compensation of critical signal properties, such as near-field and large bandwidths, which make the proposed technique able to deal with very general imaging configurations, such as near/far-range, narrow/wide-beamwidths and-bandwidths, very short aperture... Experimental results obtained at millimeter-wave are shown to demonstrate the performance and versatility of the proposed approach.

Partially Excited Antenna Array for Near-Field Patterned Focusing

“…Firstly, when the desired focusing pattern is designed, the pattern is divided into multiple focal points. The phase and amplitude distributions of the antenna array aperture are calculated using Equation (1). Since the amplitude values of some elements are small less than −10 dBW, which means that these elements contribute very little to the focusing pattern, it can cause high sidelobes around the focusing pattern.…”

“…Today, near-field focusing antennas are widely used in many applications, such as microwave imaging [1,2], wireless energy transfer (WPT) [3,4], microwave hyperthermia [5], and radio frequency identification (RFID) [6,7]. For a traditional dielectric lens antenna, the incident waves from different positions of the lens arrive at the focal point in the same phase to achieve near-field focusing [8].…”

Near-field Shaped Focusing with Planar U-slot Antenna Array of Amplitude and Phase Regulation

“…Near-field focusing antennas can be used to focus electromagnetic energy to any point in the nearfield region like lenses. They are widely applied in various scenarios, such as wireless power transfer (WPT) [1], industrial inspection [2], and microwave imaging [3]. Near-field focusing can be realized by adjusting the phase distribution of the antenna aperture, where the phase is superimposed in the same direction at the focus.…”