This dissertation describes the design and implementation of a radar simulator called Sarsim2. The radar simulator was originally developed to produce synthetic range profiles (SRPs) of complex aircraft models. It was then expanded and upgraded to generate simulated synthetic aperture radar (SAR) data.
Over the last few years a substantial amount of work has been carried out by the Radar Remote Sensing Group (RRSG) at the University of CapeTown (UCT) to produce SRPs of aircraft using an L-Band search radar of Reutech Systems. The high range resolution that can be obtained from SRP processing makes it feasible to extract characteristic features from a profile obtained from an aircraft. The ultimate aim of producing SRPs is to use these extracted features for non-cooperative target recognition (NCTR), i.e. to be able to identify an aircraft type from the echo signal received by the radar. The radar simulator was written to produce SRPs of aircraft models, which could then be used to investigate the feasibility of various aircraft-identification algorithms.
The stepped-frequency processing required to obtain SRPs of aircraft targets has initiated further research in the RRSG into more efficient stepped-frequency processing techniques, and the radar simulator has been used extensively to generate simulated data.
The RRSG group is also actively involved with SAR processing techniques, and the radar simulator has been invaluable in providing necessary simulation data to test various processing algorithms.
One of the main objectives of this simulator was to have an easy-to-use graphical interface, which can show results in real-time. This requirement makes it necessary to find some way of reducing the required computation. The solution implemented may be called WYSIWIC (what you see is what is calculated). This means that the data is only calculated to a resolution depending on the screen resolution. Only when the data is saved to disk will it be calculated and written with the required sampling rate.
Some of the features of the radar simulator include:
- Chirp, monochrome and user-defined pulse modulations
- Stepped-frequency implementation with constant or user-defined frequency increments
- Independent moving platforms with user-defined paths
- Generation of text script files
- Configurable A/D conversion
- Angle dependent radar cross section (RCS) of point targets
- Rotating antennas, spot mode SAR
- Point target and platform motion errors
- All user-defined functions can be imported by a separate text file
- Powerful image viewer which can display SAR files of practically any size
The program has been kept flexible so that features (for example using real-life antenna gain patterns) can be loaded with ease.
The graphical frontend of the simulator was initially written in C++ using the Object Windows Library (OWL) from Borland C++ 5.0, but was then rewritten with Borland C++ Builder, which made the development much easier. Borland C++ Builder (BCB) can be cnosidered as the best Rapid Application Development (RAD) tool currently available, offering visual components combined with the flexibility and speed of C++. The simulator exploits the protected memory model of 32 bit programs which has the advantages of crash protection and practically no memory restrictions. It therefore has to run under either Windows 95 or Windows NT 4.0. For portability reasons all the code (except the windows front end) has been written in ANSI C++. All processor intensive calculation routiens have been written as threads. This makes other tasks running in the background more responsive and also enables the user to abort a calculation at any time.
A second program has been included, which is basically the same program without the graphical frontend. This program is portable as it is written in pure ANSI C++. It performs like a compiler which reads the script files (text files) and writes the required simulation files to disk.