Frequency Modulated Waveforms for Integrated Imaging and Communications

Combining the functions of environmental imaging and communication requires waveforms that are simultaneously modulated to convey information while retaining desirable detection properties such as low autocorrelation sidelobes. This paper explores the use of an optimized frequency modulated (FM) chirp waveform designed for integrated imaging and communications. The waveform is radiated by a moving transmitter, such as a synthetic aperture radar (SAR) mounted on an airborne or satellite platform, and it simultaneously embeds a communication bit stream while retaining the autocorrelation properties desired for creating images of a ground scene. The transmitted chirp contains spectral nulls within its bandwidth that are created by applying a continuous offset to the phase modulation function. Within the nulled spectral regions, a second waveform modulated by a communication bit stream can be inserted. Simulated results demonstrate two techniques for creating the spectral nulls in the adapted chirp.