Linear power amplifier for high frequency ultrasound coded excitation imaging

Commercial function generators and power amplifiers are generally used in high frequency coded excitation imaging systems. In order to minimize size, reduce external noise and deliver transmit energy to transducer efficiently in a system with the coded excitation, digital waveform generator and power amplifier should be placed on a single board. The pulser with capability of doing arbitrary waveform amplification was custom-designed and developed for a high frequency coded excitation imaging system. The matching of input stage was achieved by transmission line transformer (TLT) with ferrite core. Using TLT, matching circuit became simple otherwise it would require matching circuit using lumped components. Transformers were used between stages. The 6dB bandwidth of developed amplifier was from 10MHz to 110MHz. In the pass band, the gain of amplifier fluctuated within 4dB. Wire target measurements and ex-vivo measurements on tissues clearly demonstrated its superior performance.