Arbitrary waveform generation based on phase and amplitude synthesis for switched mode excitation of ultrasound imaging arrays

The implementation of miniaturised excitation circuitry in portable systems and transducer integrated front ends is challenging due to the requirements for high voltage and high current generation. Arbitrary excitation performed using digital to analog converters and high specification amplifiers cannot be easily miniaturised. Switched excitation circuitry can easily miniaturised but requires careful waveform design to achieve arbitrary excitation. Previously, Harmonic Reduction Pulse Width Modulation (HRPWM) has been proposed to allow the design of low harmonic content switched mode excitation signals through a parameterized design process. This paper proposes the technique arbitrary-HRPWM (AHRPWM) to allow the synthesis of three and five level true arbitrary switched mode excitation waveforms. The technique is demonstrated through the design and evaluation of linear frequency modulated waveforms that have been pre-distorted to compensate for transducer characteristics. After simulating the transducers response the resulting switched mode waveforms show am 0.06% amplitude error in the time domain compared to the amplified analog waveform and -45 dB and -35 dB third harmonic powers for the three and five level switched mode waveforms respectively.