151 GHz CMOS transmitter and receiver are presented for ultra-short distance (~1 mm) contactless connection and plastic waveguide communications. To continue to scale the communication bandwidth, the 4-level pulse amplitude modulation (PAM-4) is utilized by implementing a current-mode PAM-4 modulator in the transmitter. The transmitter and receiver suffer non-linear characteristics and create amplitude distortions on PAM-4 signaling. A digital pre-distortion circuit is integrated in the PAM-4 modulator to correct such system non-idealities. 151 GHz antennas are realized on FR4HR substrate and used as air-to-air/chip-to-waveguide couplers. On top of contactless connection and plastic ribbon waveguide, plastic-embedded PCB channels are introduced by exploiting copper-coated slots on PCB and plastic ribbons to communicate through PCB substrates. The transmitter and receiver are fabricated in 28-nm CMOS process. The demonstrated system consumes 60.2 mW under 1.2 V supply while transferring 30 Gb/s of PAM-4 data, achieving 2.01 pJ/bit energy efficiency.