Enhanced Single-Sideband Time-Modulated Phased Array With Lower Sideband Level and Loss

Abstract

This article presents an enhanced single-sideband time-modulated phased array (ESTMPA) using modulating pulses with stepped waveforms. Based on the in-phase/quadrature (I/Q) complex modulation technique, this phase-only weighting array generates a scanning beam at the 1st sideband. The proposed modulating pulses realized through a reconfigurable power divider in I/Q time modulator can avoid the power loss from the switches during switch-OFF state and eliminate the maximum undesired sideband—the 5th harmonic in STMPA. As a result, it brings a power spectrum with less undesired sidebands, lower sideband level (−16.9 dB), higher harmonic efficiency (94.96%), and wider allowable signal bandwidth (eight times as wide as that of the conventional time modulated array). To experimentally verify the feasibility of the proposed design, a wideband enhanced I/Q time modulator and its corresponding eight-element ESTMPA are designed and manufactured. A detailed study on the effect of the magnitude and phase deviations in the circuit and the transition period of modulating pulse are presented. The measured results of power spectrum and radiation pattern have a good agreement with the simulated ones.