An energy-efficient 1.5-Mbps wireless FSK transmitter with A ∑Δ-modulated phase rotator

An energy-efficient PLL-based FSK transmitter is reported in this work. The PLL output signal is manipulated by a sigma-delta modulated phase rotator, whose output frequency is controlled by the input data, to produce FSK signals. Since the data is applied outside the PLL, the frequency modulation characteristics are no longer constrained by the PLL loop. Fabricated in a 0.18-mum CMOS process, the whole transmitter draws 13 mA from a 1.5-V supply. With a 1.5-Mbps data rate, the transmitter achieves an energy efficiency of 13 nJ/bit, and delivers an output power of -9 dBm.