Low-Power High-Data-Rate Transmitter Design for Biomedical Application

Abstract

For implantable and wearable biomedical applications, such as wireless neural recording and capsule endoscopy, there has been an increasing demand for the development of wireless transmitter (TX) with low power consumption and high data rate. In this thesis, two energy-efficient TXs are proposed. Firstly, a 900-MHz QPSK/16-QAM band-shaped TX will be presented. Unlike the conventional TX, injection locking coupled with quadrature modulation is utilized to achieve band-shaped QPSK/16-QAM modulation with effective sideband suppression of more than 38 dB. Fabricated in 65-nm CMOS, the TX achieves maximum data rate of 50 Mbps/100 Mbps for QPSK/16-QAM with 6% EVM, while occupying only 0.08 mm2. Under 0.77-V supply, the TX attains energy efficiency of 26 pJ/bit and 13 pJ/bit respectively with and without activating band shaping. Secondly, a multi-channel reconfigurable 401~406 MHz GMSK/PSK/QAM TX with band shaping is realized in 65nm CMOS with an area of 0.4 mm2. Using DLL-based phase-interpolated synthesizer and injection-locked ring oscillator, the TX attains 1 kHz frequency resolution as well as multi-phase output without the need of phase calibration. Through direct quadrature modulation at digital PA, the TX achieves less than 6% EVM for data rate up to 12.5 Mb/s. The band shaping maximizes the spectral efficiency with ACPR of -33 dB. Consuming 2.57 mW, the TX attains an energy efficiency of 103 pJ/bit.