Noise Radar Technology

The well-known classical pulse radar has several disadvantages. The high transmitted peak power can be easily detected and warn an enemy, and the ambiguities in both range and Doppler measurements lead to problems with unambiguous localization and tracking. For a long time researchers have tended to overcome these problems and find waveforms that will free the radar from the aforementioned issues. The design of the frequency modulated continuous wave radar with linear frequency modulation was an important step; the mean power is equal to the peak power and it is much harder to detect such radar, but range and Doppler ambiguities remain due to periodicity in the waveform repetition. The next step was the introduction of the noise radar concept. At first glance it is hard to believe that a noise signal, without any clear internal structure and well-defined instantaneous frequency, can be used for radar purposes. But thanks to the development of digital correlators which are able to compute the ambiguity function in real time, it is now possible to unambiguously estimate the range and radial velocity of the target using noise illumination. But of course one must pay a price: noise radar is limited not only by ambiguities in range and Doppler, but also in dynamic range. The strong return signal from nearby targets, or clutter, can entirely mask a weak and distant target's echoes. The second drawback is that signal processing is much more complex than in classical radars and thus the radar signal processing unit for a noise radar must have much higher computational power, which is achievable only by using modern computers equipped with graphical processing (GPU) units. The potential applications for noise radar can be vast; it is possible to use it for surveillance, traffic monitoring, and early warning and imaging (SAR, ISAR) purposes as the time on target is usually very long (hundreds of milliseconds to seconds).