A 200-pJ/b MUX-Based RF Transmitter for Implantable Multichannel Neural Recording

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents a 400-MHz energy-efficient offset quadrature phase-shift keying (O-QPSK) transmitter for implantable multichannel neural recording applications. Transmitters for these applications must operate at low power while delivering a high data rate. The proposed transmitter incorporates a phase MUX, which directly implements the phase-shift keying operation. The O-QPSK modulation signal is generated by selecting one of the four quadrature phases based on the baseband data via the phase MUX. The power amplifier adopts the inverter-type topology for it is compatible with the quasi-constant-envelope nature of the O-QPSK signal. Implemented in a 0.18-<formula formulatype="inline"> <tex Notation="TeX">$\mu{\hbox{m}}$</tex></formula> CMOS process, the whole transmitter dissipates 2.9 mA from a 1.2-V supply. With a maximum data rate of 17.5 Mb/s, the proposed transmitter achieves an energy efficiency of 200 pJ/bit and is capable of delivering an output power up to <formula formulatype="inline"> <tex Notation="TeX">${-}{\hbox{8 dBm}}$</tex></formula>. </para>