Narrow band synthetic aperture radar image formation

A description is presented of a technique of narrowband synthetic aperture radar imaging (N-SAR), also referred to as coherent Doppler tomography (CDT), which may be a good candidate for space-borne applications. Using this approach, a point spread function with a -3 dB mainlobe width of λ/5 can be attained, where λ represents the wavelength of the transmitted continuous wave signal. However, the high sidelobe level (-8 dB) in the point spread function results in an unacceptable dynamic range. Two approaches to reducing the sidelobe level are presented. One uses multiple discrete frequencies; the other uses a noncoherent subaperture processing technique. Simulation results demonstrate that the sidelobe level is substantially reduced in both methods. The price paid for this improvement in the sidelobe level is a slight increase in the mainlobe width of the point spread function