A Single-Sideband Time-Modulated Phased Array With Low Sideband Level Suitable for Wide-Bandwidth Signals

Single-sideband time-modulated phased arrays (STMPAs) are able to generate a scanned beam at the first sideband while suppressing undesired sidebands. In this article, an STMPA with very low sideband level (SBL) suitable for wide-bandwidth signals is proposed. The design utilizes time-modulated pulses with stepped waveforms, which are realized by digital attenuators. This provides more degrees of freedom to improve the performance of STMPAs compared with previous techniques. Optimization of waveforms to achieve low SBLs as a function of the number of steps is discussed. This optimization is subject to some practical restrictions stemming from the characteristics and limitations of digital attenuators. Compared with previous STMPAs designed to eliminate undesired sidebands, the proposed design results in very low SBLs while reducing the impact of aliasing for wideband signals. Quantitative analysis of hardware complexity and aliasing effects is presented to demonstrate it. To validate the analysis presented, STMPAs with four-step and eight-step waveforms were designed and fabricated. Their measured SBLs are −28.72 and −33.57 dB, respectively. Measured frequency spectrum, waveform of modulating pulse, and radiation pattern of scanned beams are all presented.