Application of coherent radar using stepped frequency modulation: an evaluation of a practical, narrowband design

Rowsell, Dean Francis (2008) Application of coherent radar using stepped frequency modulation: an evaluation of a practical, narrowband design. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (10MB)

Abstract

Coherent radar is poised to supersede traditional (typically magnetron-based) radar in a vast array of applications, that until recently could not bear the high cost of coherence. The reason for this is that the wireless communications age has accelerated the development of enabling technologies and tremendously improved associated costs. -- Coherent radar systems are capable of equaling or exceeding the performance of traditional radar, at power levels reduced by up to several orders of magnitude. To accomplish this, an equivalent energy is distributed over time using special modulation schemes, such as stepped-frequency-modulation (SFM). SFM is a multi-parameter waveform, so much of the understanding of the effects of different parameter sets can be attained through simulation and investigation of ambiguity responses. Such investigation led to the development of generalized ambiguity patterns for SFM that provide a reference for understanding the impact of changing the waveform parameters. SFM can also be inherently exploited in receiver design since its bandwidth is linearly distributed over time. Therefore, a receiver can be dynamically and synchronously tuned so that instantaneous reception is over a narrow bandwidth-effecting cost savings in the digitizing hardware. An algorithm has been developed, called an isomorphic matched filter, to support this method. -- To investigate the practical aspects of coherent radar, a research program was launched at C-CORE to design and implement a radar prototype and conduct a field assessment. This research program yielded a working prototype that was subjected to a variety of field exercises. The results showed that the performance, in terms of range and Doppler resolutions, predicted by theory and simulation was indeed realizable, and with a radar platform constructed for moderate cost. -- An SFM-based, scanning, coherent radar carries many configuration possibilities. A simple model was developed to consider various parameter sets associated with the SFM waveform and the scanning platform. The model predicts achievable resolutions and range constraints in particular. One interesting finding is that the SFM waveform does not lend itself, simultaneously, to target detection at both short range and long range, and that the signal parameters can only be optimized for one or the other. Operationally, this implies that if both near range and far range data is needed, strategies must be decided upon to render such data to the user (e.g., alternate the parameter set in successive scans). -- While the radar prototype was well-suited to fulfilling the objectives of the research program, it is not in a form suitable for demonstration in real operational scenarios. To accommodate this, the next design iteration must incorporate the following elements: azimuth scanning; a much higher level of integration in the hardware; and, support for real-time processing and rendering of the radar output. This research provides a sound foundation for further development and commercial exploitation of SFM-based coherent radar. It is recommended that such development focus on producing a prototype that can be placed in real operational scenarios in order to fully assess the utility of the technology.

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