Miniaturized design of wideband mm-wave circularly polarized transmitarray for CubeSat applications

This chapter presents a wideband millimeter-wave circularly polarized (CP) transmitarray designed for Ka-band CubeSat applications. The proposed design integrates multiple band antennas into a single wideband structure using a linear-to-circular polarization (LP-to-CP) converter. This converter, implemented on a single-layer substrate, provides angular stability up to 50° and achieves a 3-dB axial ratio bandwidth of 29% over the 29.5–39.5 GHz frequency range. The unit cell of the converter measures 0.38λ × 0.38λ × 0.15λ, where λ corresponds to a frequency of 30 GHz. A wideband 2-bit phase-quantized transmitarray is incorporated with the polarization converter, forming a CP wideband transmitarray. This array is illuminated by a wideband linearly polarized (LP) Vivaldi antenna. The transmitarray surface consists of polarization-rotating elements with dimensions of 0.3λ × 0.3λ × 0.15λ (λ at 30 GHz). The proposed CP transmitarray exhibits an axial ratio bandwidth of 27.3% (29.5–39.5 GHz) and a 1-dB gain bandwidth of 24.5% (30–38.5 GHz), with a peak gain of 21.4 dBic. Fabrication and measurement of both the LP-to-CP converter and the integrated CP transmitarray have been performed, demonstrating strong agreement between simulated and measured results.