Abstract
This paper presents an experimental Synthetic Aperture Radar (SAR) system that is under development in the Universidad Politécnica de Madrid. The system uses Linear Frequency Modulated Continuous Wave (LFM-CW) radar with a two antenna configuration for transmission and reception. The radar operates in the millimeter-wave band with a maximum transmitted bandwidth of 2 GHz. The proposed system is being developed for Unmanned Aerial Vehicle (UAV) operation. Motion errors in UAV operation can be critical. Therefore, this paper proposes a method for focusing SAR images with movement errors larger than the resolution cell. Typically, this problem is solved using two processing steps: first, coarse motion compensation based on the information provided by an Inertial Measuring Unit (IMU); and second, fine motion compensation for the residual errors within the resolution cell based on the received raw data. The proposed technique tries to focus the image without using data of an IMU. The method is based on a combination of the well known Phase Gradient Autofocus (PGA) for SAR imagery and typical algorithms for translational motion compensation on Inverse SAR (ISAR). This paper shows the first real experiments for obtaining high resolution SAR images using a car as a mobile platform for our radar.
Highlights
Synthetic Aperture Radars (SAR) typically provide a two-dimensional representation of the scatterers over an extensive area that has been illuminated with microwaves
This paper describes a method for focusing SAR images with movement errors larger than the resolution cell, without using an Inertial Measuring Unit (IMU)
Some measurements of the subsystems have been presented. This sensor is modular, compact and lightweight, so it is very attractive for use in portable applications like Unmanned Aerial Vehicle (UAV) operation
Summary
Synthetic Aperture Radars (SAR) typically provide a two-dimensional representation of the scatterers over an extensive area that has been illuminated with microwaves. For very high resolution SAR systems, the movement errors could be large enough to shift the detected target to other range cells due to non-ideal motion. An additional technique to correct these effects is needed Another solution is to use the motion information provided by an IMU to align the target response for each pulse, removing the range shift. This paper describes a method for focusing SAR images with movement errors larger than the resolution cell, without using an IMU This method is based on a combination of the well known Phase Gradient Autofocus (PGA) for SAR imagery [5, 6, 7], with typical algorithms for translational motion compensation on Inverse SAR (ISAR), such as Envelope. LFM-CW signal facilitates system miniaturization and requires low power operation, which makes it possible to install the system in an UAV
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