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This paper presents a practical implementation of an integrated MRI-compatible CMOS amplifier capable of directly driving a piezoelectric ultrasound transducer suitable for high-intensity focused ultrasound (HIFU) therapy. The amplifier operates in Class DE mode without the need for an output matching network. The integrated amplifier has been implemented with the AMS AG H35 CMOS process. A class DE amplifier design methodology for driving unmatched piezoelectric loads is presented along with simulation and experimental results. The proposed design achieves approximately 90% efficiency with over 800 mW of output power at 1010 kHz. The total die area including pads is 2 mm(2). Compatibility with MRI was validated with B1 imaging of a phantom and the amplifier circuit.

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theoretically demonstrated that, if the SOA is polarization insensitive, the total power in both harmonics is constant. Therefore, by isolating these harmonics using a bandpass filter and a polarizer, we achieved a polarization-insensitive wavelength conversion producing an output beam whose polarization state is linear for all input signal polarization states. On the other hand, this system can be placed at the input of a polarization-sensitive block in order to make it polarization insensitive, acting as an active polarization controller. Experimentally, we have implemented a scheme providing a weak polarization sensitivity in the output amplitude of about 0.9 dBm. This discrepancy is due to the polarization sensitivity of the SOA used; however, by increasing the power of the pump whose polarization coincides with the amplifier waveguide TM mode, the scheme polarization sensitivity can be reduced to zero. REFERENCES1.

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