150-GHz CMOS TX/RX with Digitally Predistorted PAM-4 Modulation for Terahertz Contactless/Plastic Waveguide Communications

In this article, 150-GHz CMOS transmitter (TX) and receiver (RX) are presented for contactless and plastic waveguide communications. The implemented system employs a four-level pulse-amplitude modulation (PAM-4) and noncoherent detection. The direct upconversion TX and self-mixing RX suffer amplitude nonlinearity and distort the carrier-modulated multilevel signals. A current-mode digital predistortion is integrated in the PAM-4 modulator to correct the nonlinearity for the carrier-modulated multilevel signaling. Coupling antennas are designed on FR4-HR substrates. The same antenna launches electromagnetic energy into plastic waveguides to extend the communication distance. A plastic printed circuit board (PCB) is introduced by inserting plastic waveguides into copper-coated slots on PCBs to realize terahertz PCB communications. The TX and RX are fabricated in the 28-nm standard bulk CMOS process. The system consumes 60.2 mW under 1.2/1.5 V supply while transferring 30 Gb/s PAM-4 data, achieving 2.01 pJ/bit energy efficiency.