A 28 GHz fully integrated GaN enhanced single-sideband time-modulated MMIC for phased array system

This paper presents a 28 GHz GaN enhanced single-sideband time-modulated phased array (ESTMPA), based on a monolithic microwave integrated circuit (MMIC), including both a time-modulated circuit and an RF front-end module (FEM). The time-modulated circuit mainly consists of a numerically controlled attenuator to balance the amplitude, compact phase shifters to generate balanced signals, a reconfigurable power divider, and a quadrature power divider. The FEM mainly consists of a low noise amplifier and a power amplifier, featuring codesign of input/output networks. Based on the in-phase/quadrature (I/Q) composite modulation technique, a stepped modulation waveform, realized by the time-modulated circuit, is used to enable a weighted array of phases. This helps generate a scanned beam at the first positive sideband and eliminate the undesired sidebands. The final MMIC-based four-element ESTMPA shows a relative suppression level of -16 dB at the positive fifth sideband and -13 dB at the zeroth sideband, and a much higher level at the other undesired sidebands. As a result, a wider signal bandwidth and a higher harmonic efficiency are achieved. In addition, the ESTMPA shows a beam sweeping angle from -30 degrees to 30 degrees in far-field measurement.