A 55nm, 0.6mm2 Bluetooth SoC integrated in cellular baseband chip with enhanced coexistence

Abstract

This paper describes a 55nm, 0.6mm2 Bluetooth SoC integrated in cellular baseband. Several techniques are used to enhance co-existence performance of Bluetooth with cellular and Wi-Fi. First is the design of current-mode interfaces from LNA to complex BPF for better linearity and the additional antialiasing LPF placed before ADC for outband rejection in the RX. Second is the use of a passive voltage sampling mixer to lower out-of-band emission noise floor in TX. Moreover, only two inductors are used, one of which is a field-cancelling inductor used in VCO layout to achieve a spur-free LO signal, minimizing magnetic coupling from other parts of SoC. The TX output power is +11dBm at BDR mode and +8dBm at EDR3 mode, with 1.5-kHz frequency drift and <;6% RMS DEVM. The RX sensitivity is better than -96.5dBm and -89.2dBm for BDR and EDR3 modes respectively. The measured BT RX sensitivity is -57dBm at BDR mode while co-existing with -5dBm of Wi-Fi 54Mbps OFDM.