Chaotic Radio Frequency (RF) Sources for Ranging and Detection (RADAR) Applications

The application of chaotic dynamics to rf technology remains unproved, to some extent because of the lack of experimental devices that can produce chaotic behavior at microwave frequencies with understandable dynamics. Ideally, an experimental rf sourcewould 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 manyother rf sources may be capable of generating chaotic output, the dynamics is likely to be high-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 thatscaling to higher frequencies can be accomplished. The construction of chaotic rf devices that are efficient, operationally stable, and produce low-dimensional waveforms is within reach using circuit design methods. We also plan to characterize the devicewith a simple binary symbolic dynamics so that, for RADAR applications, the waveform can be encoded with minimal information. Since Syncrodyne is already geared up to develop and prototype an 800 MHz HBT-based chaotic oscillator, we will performtheoretical work towards a true distributed-element design and analysis to determine how high the frequency can be scaled, up to about 10 GHz. A prototype in this phase is also possible. The commercial potential for an rf source technology that reducescost and complexity, while having increased efficiency and reduced size and weight is enormous. In personal wireless devices, for example, the efficiency of the rf power amplifiers for signals with large variations in the amplitude envelope remainsextremely low; 20 percent power-added efficiency is not uncommon. (Standards adopted for the next generation of cellular communications use signals with 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 to radically change implementation architectures. In the RF domain, this means that linear circuit approachesmust be abandoned in favor of nonlinear designs. Strongly nonlinear RF architectures are possible with amplifiers based on chaotic dynamics, but the system itself can have a linear transfer function, thus allowing for high power-conversion efficiency aswell as low signal distortion for non-constant envelope signals.