No-Need-To-Deploy UHF Antenna for CubeSat: Design Based on Characteristic Modes

This letter proposes a compact 435 MHz telemetry, tracking, and command (TT&C) CubeSat antenna, which does not require an in-orbit deployment mechanism for proper operation. It uses characteristic modes on spacecraft's body to increase the radiating aperture, resulting in a λ/4 sized antenna (as calculated along diagonal of the cube). The antenna aims to provide reliable communication, operating independently from spacecraft's orientation and does not rely on proper deployment of vulnerable mechanical components. The limited space in the launcher limits any protrusions to no more than 6 mm (1/115th of the wavelength) from the spacecraft's wall, which results in low input impedance of 0.4 - 3.2j. To overcome this issue, a differential feeding structure is proposed that incorporates a power divider with impedance matching circuit. It also incorporates a lumped capacitor that can adjust the antenna's operating frequency. The antenna offers a dipolelike radiation pattern with performances comparable to larger deployable UHF antennas. It is intended for reliable TT&C.