A 31.92% Efficiency Colpitts DCO-PA for BLE TX with Implicit RX Clock Generation Using DM-to-CM Mode-switching

Ultra-low-power (ULP) transceivers (TRX) play a crucial role in Internet of Things (IoT) applications, where Bluetooth Low Energy (BLE) is currently the most popular low-power short-range communication protocol [1–6]. In a conventional TX (Fig. 1(a)), considerable power is consumed into PA driving stages (Pdc,Drive), primarily an RF oscillator and possibly a frequency divider plus buffers in cascading stages, which cannot scale with output $P_{\text {RF }}$ and thus limit the system efficiency. Function-reuse DCO-PAs [1, 3] (Fig. 1(b)) are proposed to merge the driving capability of the RF oscillator into the PA making it self-driven, thereby reducing the Pdc,Drive for scalability and efficiency. However, there are still unsolved issues with recent DCO-PAs: (1) The DCO-PA [1, 3] cannot generate the local oscillator (LO) signal for RX resulting from the inevitable antenna leakage due to the simultaneous power-on of oscillating and PA when directly utilized DCO-PA in RX mode; (2) The source-to-gate transformer (xfmr)-feedback DCO-PA [1] exhibits low efficiency owing to unexpected source swing limiting drain peak output.