Nonlinear synthetic wideband waveforms

Abstract

Radars commonly use wide bandwidth pulses to attain high range resolution. However, when such wideband pulses are unavailable (or otherwise undesirable), high range resolution can still be achieved by coherently combining a sequence of narrowband pulses spanning the desired bandwidth. Collectively, such narrowband pulse sequences are said to compose a "synthetic wideband waveform" (specific variants are also known by the names "stepped frequency waveform", "frequency jump burst" and "frequency jump train"). Prior publications and reports have examined synthetic wideband waveforms that distribute energy uniformly over the frequency band. Such waveforms require heavy spectral weighting, highly overlapped pulses and/or nonperiodic pulses to control the range sidelobes and grating lobes; unfortunately, undesirable attributes are associated with each of these. We formulate synthetic waveforms that distribute energy nonuniformly over the desired frequency band. These new waveforms are shown to offer improved performance (i.e., lower range sidelobes, higher gain, higher range resolution and/or reduced grating lobes) when compared with traditional approaches.