ABSTRACT
This chapter presents a multimode low-power radio transmitter (TX) which is designed for implantable biomedical applications. It reviews the conventional TXs, including mixer- and phase-locked-loop (PLL)-based topologies, and describes their architecture trade-offs. The chapter focuses on the design of a frequency-shift-keying (FSK)/phase-shift-keying (PSK) dual-mode transmitter, and presents a dual-mode FSK/PSK transmitter for higher flexibility in modulation. It proposes a MUX-based transmitter that can be adopted as a dual-mode FSK/PSK transmitter for uplink transmission. The selection of operation frequency for an implanted transmitter must consider the signal propagation characteristics of the human body, circuit power consumption, and implantable antenna size. In many low-power low-data-rate wireless communication systems for biomedical applications, amplitude-shift-keying (ASK) modulation is often used because of its low power consumption and fast turn-on time. The modulation quality of RF transmitters is significantly influenced by the quadrature gain and phase accuracy of the analog baseband and local oscillator (LO) signals.
