A low profile broadband UHF canted turnstile antenna phasing network

A broadband UHF antenna-phasing network providing equal amplitude and quadrature phase shifts to four radiating elements of a canted turnstile antenna was designed and prototyped. The antenna was designed for use on a pair of CubeSats on the ORS Tech 1 and 2 mission, which launched in November 2013. The design consists of a transmission line transformer and a pair of broadside-coupled quadrature hybrids operating over 240 MHz to 390 MHz with a worst case amplitude imbalance within ±0.8 dB and a phase imbalance within ±2.5°. The RF power handling capability is 25 W, continuous wave (CW), and is achieved in a form factor of less than 5 cm × 5 cm × 0.4 cm, ideally suited for low profile applications. The radiating elements, made of flexible tape, are mounted directly on the phasing network circuit board, eliminating the need for coaxial feeds and allowing stow and deploy capability. The prototype was installed in a mockup of the CubeSat, including deployed solar panels and tested at an antenna range facility.