Near-field imaging of one-dimensional aperture synthesis radiometers

For synthetic aperture radiometers under far-field (FF) condition, the relationship between the visibility and the brightness temperature is a Fourier Transform. However, it is no longer valid when synthetic aperture radiometers are applied at short distances. A novel method based on a reference position for near-field (NF) imaging of one-dimensional aperture synthesis radiometers (ASR) is proposed. By subtracting the phase of NF visibility samples of a point source at the reference position from the phase of NF visibility samples of the imaged scene, the relation between the brightness temperature and the NF visibility can be represented by another form of Fourier Transform. Then direct DFT inversion algorithm is applied. Simulations and NF experimental results demonstrate the validity of the method for both point and extended sources. The method can be used not only in those applications at NF region of ASR, but also indoor performances test of spaceborne ASR.