Integrated Demodulator for Manchester-Coded AM Signals with Clock Retrieval in US Applications

Data transfer and clock generation is a general challenge that must be tackled in implantable devices. In this work, we propose an integrated demodulator for Manchester-coded AM signals. The developed demodulator for the data Down-Link of an implantable device based on ultrasound (US) with a power consumption of 115 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{W}$</tex> fits into an area of 378.5 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\times$</tex> 136.9 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}^{2}$</tex> and uses a robust design to cope with variations in the input signal due to misalignment. It is designed to receive an envelope, which provides the Manchester-coded data with an amplitude margin of 30 mV, and to output a retrieved clock together with the demodulated data, thereby rejecting fluctuations on a close-to-DC reference, validated with frequencies of up to 20 Hz. The circuit functionality is verified by simulation in 0.18 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu\mathrm{m}$</tex> CMOS technology, applying the upper sideband of an AM modulated signal with data rates of 9 to 15 kHz.