Calibration for Single-Sideband Time-Modulated Phased Arrays to Improve the Frequency Spectrum by Modifying the Time-Modulating Waveforms

Single-sideband time-modulated phased arrays (STMPAs) can generate a high-efficiency scanned beam at the first sideband and suppress undesired sidebands. However, they have certain imperfections, such as fabrication errors, assembly errors, and imperfect isolation, which deteriorate the frequency spectrum. This article proposes a calibration technique for STMPAs achieved by modifying the time-modulating waveforms. A high degree of freedom for the time modulator in STMPAs provides the possibility to improve the frequency spectrum without the use of any additional hardware. Based on mathematical formulations with the imperfections involved, quantitative analysis of the imperfection is carried out to calculate the practical spectrum. Different types of common imperfections are then analyzed, and the corresponding methods of calibration are presented. An eight-element STMPA was fabricated to test the effectiveness of the calibration.