Direct digital RF transceiver technology for millimeter-wave DBF systems

Digital RF technology has been developed and has been applied to below 6 GHz wireless applications. By replacing the IC die consumptive RF/analog circuit blocks by digital signal processor and circuit, digital rich/small transceivers can be realized. Since the foundation of this technology is based on the Nyquist theory, the operational frequency of the circuit has been limited by the Nyquist frequency (=1/2 of sampling clock frequency). As a result, the maximum operational RF frequency of existing digital RF technology was below 6 GHz. In this paper, a new direct digital RF technology that utilizes the higher-order Nyquist zones is introduced. This technology enables handling RF signal in beyond Nyquist frequency range which means over 6 GHz range. The results of fabricated 26/28 GHz-band transmitter/receiver are reviewed. Since the transceiver architecture with the proposed technologies does not require an RF local oscillator and up/down converters, it is suitable for microwave/millimeter-wave multi-antenna systems such as next generation satellite on-board digital beam forming and Beyond 5G fully digital Massive multiple-input multiple-output systems.