I. Introduction
One of the significant problems with medical ultrasound systems is achieving a sufficiently high imaging depth for the system to be useful, while maintaining a sufficient resolution. The imaging depth may be improved by increasing the power of the transmitted pulse, but for safety reasons there are limits on how much power can be used. Therefore, to increase the imaging depth beyond this limit requires the use of longer pulses, which contain more energy. However, using a longer pulse results in a decrease in the available resolution.