Omnidirectional circularly-polarized conformal microstrip array for telemetry applications

Arbitrarily-oriented satellites and space vehicles such as missiles and rockets require an omnidirectional antenna to maintain a communication link with a central receiving unit. To avoid selective reception, a circularly-polarized (CP) omnidirectional antenna is often desirable. In designing a CP microstrip patch array, the design of each array element is crucial in yielding a good tradeoff between a low reflection loss and a low axial ratio. To yield a high gain, it is also important to minimize mismatch in the feed network. The analysis at the subarray level is often required to assess the effect of mutual coupling between patches. This paper examines the design of CP arrays at the element as well as the subarray level. We demonstrate how the design process can be enhanced by the use of a powerful computed-aided design (CAD) software tool for designing microstrip antennas. By assuming a flat mounting surface first in the design process, our results show that the effect of the curvature is negligible for mounting cylinders with radii greater than one guided wavelength.