A 700 pJ/bit, 2.4 GHz, narrowband, PLL-free burst mode transmitter based on an FBAR with 5μs startup time for highly duty-cycled systems

This paper presents a PLL-free transmitter based on an FBAR achieving a 5μs startup time to reduce the crystal oscillator power overhead which degrades the energy efficiency for heavily duty cycled systems. The TX upconverts a FSK-modulated FBAR DCO signal with the IF output of a Phase Switching Divider (PSD) injection locked to the DCO. The PSD has a division step of 0.2 to circumvent the limited FBAR tuning range that prevents addressing all the channels in the various bands between 2.36 and 2.5 GHz. Integrated in a 65nm technology, the TX outputs -1dBm and consumes 9.2mA at 1.2V. Further, the TX is capable of data rates up to 16 Mbps leading to a peak energy efficiency of 700pJ/b as well as a multi-fold reduction in the mean power dissipation at lower mean data rates.