Piotr Serafin

Airborne radar terrain imaging system

Synthetic aperture radar (SAR) imaging systems are becoming increasingly useful in military and civilian surveillance applications. Installation of a SAR system on a miniature unmanned aerial vehicle (mini UAV) enables high resolution terrain imaging in adverse observational conditions, e.g. at night, in fog or in smoke, where classical or infrared cameras would be useless. Use of a small and relatively low-cost radar platform allows for reduction of the mission costs and reduces the risk of detection and destruction of the carrier by the enemys air defence. The paper presents a concept, a structure, and the most important elements of the UAV-based SAR terrain imaging system, currently developed in a project WATSAR, jointly realized by the Institute of Radioelectronics of the Faculty of Electronics, Military University of Technology, Warsaw, Poland and a Polish private company WB Electronics S.A., under a grant financed by the National Centre for Research and Development. It is assumed that the system will provide high resolution radar images, comparable with aerial photographs, which will be used for tactical scale military reconnaissance. The SAR images from the developed system can also augment multisensory data processed in Battlefield Management Systems (BMS), supporting decision processes on contemporary battlefield and increasing situational awareness of individual soldiers.

Chosen results of flight tests of WATSAR system

The paper describes a Synthetic Aperture Radar system currently developed by the Military University of Technology and a Polish private company WB Electronics S.A. in a frame of a project under acronym WATSAR. The project is aimed at designing, development and testing of a terrain imaging radar system operating from a miniature UAV. The paper presents structure and way of operation of the system and its current state of development. The main focus of the paper is directed onto presentation of radar images obtained during two flight campaigns realized in May and July 2015. The paper addresses also the algorithms used for SAR processing and the adopted methodology of in-flight experiments.

Inertial navigation system for radar terrain imaging

The article presents a navigation system used to improve the quality of terrain images obtained from a Synthetic Aperture Radar (SAR) installed on a miniature unmanned aerial vehicle. An inertial navigation system is used to determine the flight path deviations from an assumed straight line. Calculated position corrections are used to correct the phase of the received echo signal in order to get a focused SAR image. The paper describes chosen results of in-flight experiments, presenting the influence of navigation correction on SAR images.

A multichannel receiver application for platform motion compensation in Synthetic Aperture Radar

Synthetic aperture radar (SAR) is an advanced radar technique that provides high resolution radar images from an airborne or spaceborne platform. The quality of the radar image, however, is strongly affected by motion errors of the radar carrier. One of the ways to reduce those effects is to utilize information from carrier onboard sensors (inertial navigational systems - INS) to estimate phase errors and compute phase corrections for the processing algorithm. In order to improve the image quality and reduce the residual phase errors a variety of autofocus techniques is applied. Those are mainly based on estimating phase errors from one channel signal. This paper presents a method to compensate platform motion errors based on application of an auxiliary receiving channel. Simulation results of such a system are presented in the paper.

3-D inverse synthetic aperture sonar imaging

The article presents an experimental sonar high resolution imaging system capable of producing three-dimensional images of observed objects. The system works in an inverse synthetic aperture configuration with rotating object. In order to achieve a 3-D image the vertical position of the sensor changes during the observation. The architecture of the ultrasonic sensor, simulation as well as experimental results are presented.

Chosen results of field tests of synthetic aperture radar system installed on board UAV

The paper presents a synthetic information on a UAV-based radar terrain imaging system, its purpose, structure and working principle as well as terrain images obtained from flight experiments. A SAR technology demonstrator has been built as a result of a research project conducted by the Military University of Technology and WB Electronics S.A. under the name WATSAR. The developed system allows to obtain high resolution radar images, both in on-line and off-line modes, independently of the light conditions over the observed area. The software developed for the system allows to determine geographic coordinates of the imaged objects with high accuracy. Four LFM-CW radar sensors were built during the project: two for S band and two for Ku band, working with different signal bandwidths. Acquired signals were processed with the TDC algorithm, which allowed for a number of analyses in order to evaluate the performance of the system. The impact of the navigational corrections on a SAR image quality was assessed as well. The research methodology of the in-flight experiments of the system is presented in the paper. The projects results show that the developed system may be implemented as an aid to tactical C4ISR systems.

Object Georeferencing in UAV-Based SAR Terrain Images

Abstract Synthetic aperture radars (SAR) allow to obtain high resolution terrain images comparable with the resolution of optical methods. Radar imaging is independent on the weather conditions and the daylight. The process of analysis of the SAR images consists primarily of identifying of interesting objects. The ability to determine their geographical coordinates can increase usability of the solution from a user point of view. The paper presents a georeferencing method of the radar terrain images. The presented images were obtained from the SAR system installed on board an Unmanned Aerial Vehicle (UAV). The system was developed within a project under acronym WATSAR realized by the Military University of Technology and WB Electronics S.A. The source of the navigation data was an INS/GNSS system integrated by the Kalman filter with a feed-backward correction loop. The paper presents the terrain images obtained during flight tests and results of selected objects georeferencing with an assessment of the accuracy of the method.

Some issues of continuous wave synthetic aperture radar range resolution

In this paper the issues of frequency modulated continuous wave synthetic aperture radar range resolution are discussed. A method of acquiring the requested range resolution by dividing the sounding signal into several sub-bands with simultaneous or sequential transmission is proposed. Necessary changes to SAR image synthesis algorithm are considered.

Synthetic aperture radar raw signal simulator for both pulsed and FM-CW modes

Simulated raw radar signals prove to be very useful at the first stages of testing radar signal processing algorithms and procedures. This is particularly true for synthetic aperture radar (SAR), where the costs of real signals acquisition are very high due to the costs of building the system as well as the costs of mission (air or space-borne). This paper describes a multifunctional SAR raw signal simulator that has been used for the verification of SAR image synthesis algorithms. Generated signals can be imitated for pulsed as well as FM-CW radars both in SLAR and squinted cases, it is also possible to choose between video and intermediate frequency signals. The simulator allows us to generate echo signals from stationary and moving targets. The user is able to differentiate the statistic properties of received echo signals for each target, thus allowing us to generate different types of reflecting surfaces. If present, a real raw SAR signal can be merged with a simulated one to produce more complicated scenarios. The paper presents results of the simulation of raw signals and their image after SAR processing.

A real time SAR processor implementation with FPGA

Great numerical complexity is a characteristic of synthetic aperture radar (SAR) image synthesis algorithms that poses a particularly serious problem for realtime application. Advances in the operating speed and density of the field programmable gate arrays (FPGA) have allowed many high-end signal processing applications to be solved in commercially available hardware. A realtime SAR image processor was designed and implemented with the commercial off the shelf (COTS) hardware. The hardware was based on the Xilinx Virtex 5 FPGA devices. Under the assumption of squinted SAR geometry and range migration effect present the SAR image synthesis algorithm was developed and implemented. The results of the processor tests conducted with simulated and real raw SAR signals are presented in the paper.