A 2.4 GHz Power Receiver Embedded with a Low-Power Transmitter and PCE of 53.8%, for Wireless Charging of IoT/Wearable Devices

This article presents a 2.4 GHz and high-efficiency wireless power receiver (Rx) integrated with a low-power transmitter (Tx) for wireless charging of the Internet-of-Things (IoT) or wearable devices. A single pole double throw (SPDT) circuit isolates the operation of the Rx from Tx, thereby offering the capability of sharing antenna between them. The Rx employs a high-efficiency radio frequency (RF)-dc converter, which is facilitated with threshold voltage cancellation technique for enhancing the efficiency, and adjustable internal impedance matching network to compensate the nonlinear behavior of the input impedance with respect to input power level. In addition, it includes a boost dc-dc converter to charge the storage element with a fixed voltage and current. The Tx utilizes a low-power phase-locked loop (PLL) and a class-D power amplifier (PA). Several techniques are adopted to achieve low power consumption. The chip is implemented in a 180 nm CMOS process with a die size of $2.3\,\,\mathrm {mm} \times 5\,\,\mathrm {mm}$. The Rx shows the measured RF to dc maximum power conversion efficiency (PCE) of 53.8% at the input power level of 0 dBm. The Tx achieves a variable output power range of -10 to 10 dBm, while consumes 4 and 23 mA at 0 and 10 dBm output power, respectively.