Miniaturized UHF microstrip antenna for a Mars mission

The JPL/NASA Advanced Technology Demonstration (ATD) Program is planning a Mars Sample Return (MSR) mission circa 2005. This mission will have a rover on Mars to pick and place soil samples into a small spherical canister (16 cm diameter), which will be ejected into Martian orbit and retrieved by an orbiting spacecraft. This spacecraft will than bring the canister back to Earth for sample analysis. During canister ascent toward the orbiting spacecraft, a UHF transponder/beacon transmitt/receive signal is needed from the canister. This calls for a miniaturized low-profile antenna with an omni-directional pattern to be mounted onto the outer skin of the small canister. Antenna miniaturization techniques used on this circular patch are two fold: high dielectric-constant substrate material and multiple slats on the patch. This paper presents an antenna that combines these two techniques with dual-frequency and dual-polarization capabilities. The radiation characteristics of this antenna, when mounted on the small canister, as well as on flat ground planes of various sizes, are discussed. The bandwidth and efficiency performance and thermal effect of this antenna are also presented. In general, the antenna radiates a nearly omni-directional pattern with good efficiency and cross-polarisation characteristics.