Crystal-free narrow-band radios for low-cost IoT

A transceiver was designed and fabricated in 65 nm CMOS to verify the feasibility of using a free running, on-chip LC tank as the local oscillator in an IEEE 802.15.4 transceiver. The elimination of the off-chip frequency reference is possible while still using a standards based narrow-band architecture. A free running LC tank is shown to have frequency stability better than ± 40 ppm in the absence of temperature changes. Demodulator-based feedback is implemented to allow a receiver to track transmitter drift due to varying environmental factors and phase noise. The modulation accuracy of a free-running open loop Minimum Shift Key (MSK) transmitter is shown to be within the limits set by IEEE 802.15.4.