Propagation and Clutter Considerations for Long Range Radar Surveillance Using Noise Waveforms

Open Access
Author:
Allebach, Joshua M
Graduate Program:
Electrical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 03, 2016
Committee Members:
  • Ram Mohan Narayanan, Thesis Advisor
  • Timothy Joseph Kane, Committee Member
  • Ram Mohan Narayanan, Committee Member
Keywords:
  • Radar
  • Noise Radar
  • Long Range Radar
  • Noise Waveform
Abstract:
The use of noise waveforms is investigated for long range radar surveillance. In addition to the noise signal, a chirp waveform was also simulated for the various scenarios to act as a direct comparison of traditional radar signals. The correlation and relative ratio of received to transmitted power was found for the two waveforms after reflecting from simple targets and terrain. For the simple shapes, the correlation of the two signals were similar in value and pattern with respect to incidence angle. The reflection from terrain gave smaller correlations for the noise waveform indicating that it may be less susceptible to false alarms when terrain is considered clutter. Advanced simulations were then run with a realistic hummer target and terrain clutter model. Accounting for the atmospheric propagation loss, system gains, and receiver noise, the probability of detection and false alarm were found to create receiver operating characteristic curves. It was found that the noise waveform performs as well as the chirp for cases of strong clutter response, and much better for cases of weak clutter response. Next, modeling radar propagation as a series of cascaded two-port devices was explored. This allowed different sections of propagation, such as through air or rain, to be computed separately for a particular wavelength and then combined together to form a set of system parameters. The first radar that was modeled was forward-looking which examined an air-rain-air-target scenario. The system parameters for this case were computed for various rain rates and rain path lengths then applied to the noise and chirp waveforms. It was found the both the noise and chirp signals resulted in similar correlations with respect to path length and rain rate. The final radar that was modeled was down-looking where the waveforms were reflected and transmitted through different layers of soil with various moisture content. The correlation of both waveforms were similar in that they varied with path length due to the phase introduced by the system S11 parameter. However, the noise signal correlation was consistently lower than the chirp's. This again indicates that the noise waveform may be a better alternative for reducing clutter false alarms. Finally, the use of double spectral processing for determining target ranges was investigated in comparison to the use of cross-correlation. It was found that while the double spectral processing method efficiently determines target range, it produces echo responses in the case of multiple targets which may cause false alarms. Additionally, this method has lower peak-to-average responses than the correlation for noisy return signals, again increasing the false alarm rate.