A Broadband Phased-Array Antenna System Employing Frequency-Upconverted Local Signals With Phase Difference

This paper proposes a novel configuration for a phased-array antenna system (PAS) that achieves ultrabroadband transmission using millimeter-wave (mm-wave) and quasi-mm-wave. Since a PAS is expected to employ an unprecedented number of antenna elements to compensate for propagation loss in high-frequency bands, the configuration must be compact and cost effective. A PAS that employs radio frequency (RF) phase shifters to control the phase of RF carriers is a promising approach for broadband transmission because it needs to control only the phase of a continuous wave signal and not that of the broadband signal. In the proposed configuration, direct digital synthesizers (DDSs) are employed to generate phase-controlled local signals with a lower frequency than the carrier frequency. The signal is upconverted to an RF carrier frequency. More specifically, a formed beam using RF radiated signals with mm-wave or quasi-mm-wave is steered by the DDS in a precise phase-controlled manner. To confirm the feasibility of the configuration, a four-branch PAS transmitter is configured and tested in a 28-GHz operating band. The results verify that the proposed configuration is applicable to a PAS that operates in a broadband at high frequency.