Disclosed is a method of generating electrical signal waveforms by a generator. The method includes storing phase points of first and second digital electrical signal waveforms in first and second lookup tables. The first and second digital electrical signal waveforms are represented by a predetermined number of phase points that define wave shapes. At each clock cycle, a digital synthesis circuit retrieves phase points from the first and second lookup tables and the digital processing circuit combines phase points from the first and second lookup tables. A digital-to-analog converter (DAC) circuit converts the combined phase point into an analog signal. The analog signal is configured to drive a first and second ultrasonic transducer.