Development of Advanced Radar Technologies for Missile Defense

There is currently interest in using alternative waveforms in radars. Chaotic waveforms are one class that are being considered because of their correlation properties. The application of chaotic dynamics to rf technology remains unproved, to some extentbecause of the lack of experimental devices that can produce chaotic behavior at microwave frequencies with understandable dynamics. Ideally, an experimental rf source would be capable of operating at microwave frequencies, have a low-dimensional dynamics(with a nearly 1-d Poincar¿ return map and binary symbolic dynamics), and have high power-conversion efficiency. Although traveling wave tubes, klystrons, and many other rf sources may be capable of generating chaotic output, the dynamics is likely to behigh-dimensional. A more tractable approach to be used at this stage is circuit design. Our goal is to develop a distributed element design at above 1 GHz, so that scaling to higher frequencies can be accomplished. The construction of chaotic rf devicesthat are efficient, operationally stable, and produce low-dimensional waveforms is within reach using circuit design methods. We also plan to characterize the device with a simple binary symbolic dynamics so that, for RADAR applications, the waveform canbe encoded with minimal information. Since Syncrodyne is already geared up to develop and prototype an 800 MHz HBT-based chaotic oscillator, we will perform theoretical work towards a true distributed-element design and analysis to determine how high thefrequency can be scaled, up to about 10 GHz. The commercial potential for an rf source technology that reduces cost and complexity, while having increased efficiency and reduced size and weight is enormous. In personal wireless devices, for example, theefficiency of the rf power amplifiers for signals with large variations in the amplitude envelope remains extremely low; 20 percent power-added efficiency is not uncommon. (Standards adopted for the next generation of cellular communications use signalswith high peak-to-average power ratios. Such signals are necessary to increase bandwidth efficiency.) Because it is not possible now to change the standards, the only option available to achieve comparable battery life to voice-only handsets is toradically change implementation architectures. In the RF domain, this means that linear circuit approaches must be abandoned in favor of nonlinear designs. Strongly nonlinear RF architectures are possible with amplifiers based on chaotic dynamics, but thesystem itself can have a linear transfer function, thus allowing for high power-conversion efficiency as well as low signal distortion for non-constant envelope signals.