Abstract:
Phased arrays were used to locate waterborne targets, and to focus ultrasonic fields onto the targets using phase conjugation in computer simulations. Array performance was evaluated in the presence of small uncertainties added to the amplitudes and phases of the array elements. For the cw case, the free-space Green's function was used to calculate the conjugated field in space. The propagation of a wideband pulse utilizing time reversal concepts is simulated using a finite-difference code that allows the introduction of inhomogeneous media. Again, the performance of the array with uncertainties in the phase, amplitude, and pulse-shape information is studied. The focusing capability of a high-intensity phase conjugation array operating in the nonlinear regime will suffer from the nonlinear response of the propagating medium and transducer devices. This study examines the performance penalties of uncertainties in the linear regime as a first step to implementing a digital time-reversal system with high-intensity, nonlinear arrays in the laboratory. [Work supported by the ONR.]