A 1.1-mW-RX -81.4-dBm Sensitivity CMOS Transceiver for Bluetooth Low Energy

This paper presents a fully integrated low-power 130-nm CMOS transceiver tailored to the Bluetooth low energy (BLE) standard. The receiver employs a passive front-end zero-IF architecture, which is directly driven by a quadrature voltage-controlled oscillator (QVCO) without any buffering stage. The QVCO, embedded in a fractional-phase-locked loop (PLL), employs a passive network to cancel the parasitic magnetic coupling between the two cores so as to keep the quadrature phase error below 1.5 degrees. The PLL exhibits a high loop bandwidth of 1 MHz to sufficiently reduce the frequency pulling effects due to close-by interferers. The transmitter uses a direct-modulation Gaussian frequency-shift keying scheme in which small PMOS-based cells modulate the output signal of one of the cores of the QVCO. In the baseband section, the transceiver employs a 4-bit phase-domain ADC based on novel linear-combiner topology to generate the required phase rotations. The proposed combiner operates in current domain and does not employ resistors, leading to a power- and area-efficient demodulator implementation. The complete receiver achieves a sensitivity of -81.4 dBm and fulfills the BLE requirements on interference blocking. It consumes 1.1 mW from a 1.0-V supply and has a similar power efficiency as recent super-regenerative receivers that are much more susceptible to interferers. The transmitter delivers 1.6-dBm output power to a differential 100 Omega and consumes 5.9 mW, which implies a total efficiency of 24.5%.