An Ultra Low Energy FSK Receiver With In-Band Interference Robustness Exploiting a Three-Phase Chirped LO

An ultra-low-energy Binary Frequency Shift Keying (BFSK) receiver is proposed. It features improved in-band interference tolerance by chirping the transmission frequency. To reduce the receiver power consumption, a novel three-phase passive mixer along with a three stage digitally controlled ring oscillator is proposed, while still allowing quadrature detection. A mixer-first direct conversion receiver architecture moves the required gain to lowest frequency and lowest bandwidth to reduce power consumption. A low power flip-flop based BFSK demodulator is proposed that reduces the baseband power further. The receiver is designed and fabricated in a 65 nm complementary metal-oxide-semiconductor process. It consumes 219 μW from 1.2 V power supply, while having a sensitivity of -70 dBm for a bit error rate of 0.1% at 2.4 GHz. Except the off-chip 64 MHz clock generation, the total receiver requires 27 pJ/bit. Using a chirped clock spreading of 360 MHz and chirp repetition rate of 1 MHz, it can tolerate up to -8 dB signal to interference ratio for all interferer frequencies. This is 13.5 dB better than previously reported in literature and 12 dB better than ideal noncoherent BFSK receiver interference robustness.