Over-the-Air Waveform Synthesis and Calibration for D-Band Digital Arrays with Imperfect Low-Resolution Digital-to-Phase Modulation

Digital beamforming solutions above 100 GHz require large arrays with high power consumption and control requirements. An alternative is to eliminate excessive amplitude and phase weight calibration per element in favor of low-resolution (2-bit) control per element to maintain manageable power consumption across N elements. Spatial linear combinations of 2-bit phase-modulated signals can compose complex communication waveforms but suggests precise alignment of the individual elements, which in turn requires accurate calibration. We find that directional complex communication waveforms can be generated with obfuscated digital alphabets formed using over-the-air (OTA) measurements of the possible digital phase states in a 4-element antenna array. Imperfect element-to-element variation is found to improve the EVM. We synthesize a complex root-raised-cosine pulse-shaped waveform in different directions. We illustrate a 125 Mb/s 32-QAM constellation with EVM of 7.9% at 112.8 GHz.