A 0.7-2.5GHz NB-loT/GNSS/BLE Hybrid PLL with PA Pulling Mitigation and Out-of-Band Phase Noise Reduction

A 0.7-2.5GHz NB-IoT/GNSS/BLE hybrid PLL with a single D/VCO is implemented in 28nm CMOS. With careful frequency planning, the PA pulling effect is mitigated by using a multi-mode divider chain. A divider-by-2.5 relaxes the tuning range requirement of the D/VCO and mitigates the PA pulling for NB-IoT HB band, while a divider-by-6 is designed for NB-IoT LB. With an 8-tap FIR filtering method, a wideband fractional-N PLL is designed without increasing the out-of-band phase noise. The proposed PLL consumes the maximum 4.7mW with 0.9V supply. Experimental results show that the PLL meets the phase noise and spur requirements of the NB-IoT/GNSS/BLE standards.