A 2.4 GHz Wide-Range CMOS Current-Mode Class-D PA with HD2 Suppression for Internet of Things Applications

Area of Science:

• Integrated circuit design
• Wireless communication systems
• Radio frequency engineering

Background:

• Short-range Internet of Things (IoT) sensor nodes require energy-efficient, wide-range output power for ubiquitous wireless sensor networks (WSNs).
• Integration on a single chip is crucial for wireless body area networks (WBANs) and wireless personal area networks (WPANs) using low-power Bluetooth (BLE) and Zigbee.

Purpose of the Study:

• To propose a fully integrated transmitter (TX) utilizing a digitally controllable current-mode class-D (CMCD) power amplifier (PA).
• To achieve second harmonic distortion (HD2) suppression for reduced VCO pulling and compliance with harmonic regulations.
• To enhance performance for BLE and Zigbee standards in WBANs and WPANs.

Main Methods:

• Development of a CMCD PA with 7-bit reconfigurable slices (differential/single-ended).
• Implementation of duty cycle distortion compensation for HD2 suppression.
• Integration of an HD2 rejection filter and a modified C-L-C low-pass filter (LPF).

Main Results:

• Achieved a wide output power (P_OUT) range from 12.1 to -31 dBm.
• Maximum efficiency of 39.8% at 12.1 dBm P_OUT with 41.1 mW power consumption.
• Calibrated HD2 level of -82.2 dBc at 9.93 dBm P_OUT, yielding a TX figure of merit (TX_FoM) of -97.52 dB.

Conclusions:

• The proposed integrated TX meets regulatory requirements with higher-order harmonic levels below -41.2 dBm at 12.1 dBm P_OUT.
• The design offers significant improvements in efficiency, output power range, and harmonic suppression for IoT applications.
• The reconfigurable CMCD PA architecture provides a flexible and robust solution for modern wireless communication standards.