Watt-Level, Direct RF Modulation in CMOS SOI with Pulse-Encoded Transitions for Adjacent Channel Leakage Reduction

This article reports signal processing and circuit techniques for direct RF signal modulation. A pulse-encoded transition (PET) technique is introduced to reduce undesired harmonic distortion (HD) and adjacent channel leakage ratio (ACLR) generated by the direct RF modulation. To enable PET RF switching, two variations of a high-power, stacked-FET switch modulator, an 8-and 12-device stack, are designed in 45-nm silicon on insulator (SOI) CMOS. The switch design uses a tapering design to significantly improve power handling with minimal impact to switching speed. The modulators have P1 dB values between 34 and 39 dBm while demonstrating a modulation bandwidth of nearly 500 MHz with a 1-GHz carrier. The input referred third order intercept point (IIP3) is between 46 and 61 dBm. Additionally, ACLR measurements of up to-50 dBc are demonstrated using the proposed PET technique at 30-dBm output power. To the best of our knowledge, this is record power handling and ACLR for a CMOS switch.