Tat-Jin Teo

Angular Spectrum Decomposition: Improving the Resolution

Angular spectrum decomposition is a technique which is being used to represent a given wave field the way a spectrum is used to represent a given time varying signal. This technique can reconstruct a source from the measured field on a plane. This paper deals with the resolution aspect of the reconstruction. In particular, two methods to improve the resolution of the reconstruction are described and substantiated with simulations. The first concerns the use of multiple frequency and the second involves the use of multiple element spacing in the detecting array.

Multifrequency holography using backpropagation

The technique of wavefield backpropagation has been used quite extensively in the literature. We report on an analytical study of the resolution properties of this technique. Backpropagation as a form of holographic reconstruction suffers from poor axial resolution. We derive expressions for both the axial and the lateral resolutions. We also show that the axial resolution can be substantially improved by the use of multiple frequencies. We derive an expression relating the resolution and bandwidth.

Range estimation using backpropagation

The method of backpropagation is used to estimate the range between two planar surfaces. This method is shown to be more tolerant in a noisy environment than another method that uses the spatial derivative of the measured wave field to estimate the range.