A narrow band imaging technique for passive radar

In this paper we report on initial results into Doppler imaging, a technique by which both down and cross-range resolution are obtained with low bandwidth waveforms. Conventional radar imaging utilizes aperture synthesis to obtain cross-range resolution and relies on wideband waveforms for the downrange resolution. More recently, tomography has been proposed an alternative able to generate high-resolution imagery but without necessarily requiring wideband waveforms. Here we introduce the theory behind a third alternative, Doppler imaging and consider how it might be applied to passive bistatic radar. We present results that include the 2D image of two point targets separated by just 0.6 m illuminated using a pure tone signal in an anechoic chamber. The resolution limits using the technique are also shown, using a Fourier domain representation.