A miniaturized Global Positioning System (GPS) antenna array is being developed for use on aircraft on which the room available for installation of this or any other equipment is severely limited and there is a requirement for an anti-jamming capability. This miniaturized GPS antenna array is, more specifically, a controlled-reception-pattern antenna array (CRPA), which affords a capability for (1) electronic beam forming to maximize the signals received from GPS satellites and/or (2) electronic null forming to minimize signals received from jamming transmitters or to suppress multipath signals. Heretofore, it has been possible to equip some aircraft with fixed-reception-pattern antenna arrays (FRPAs) but not with CRPAs, which have tended to be larger. It is envisioned that the present development effort will eventually yield anti-jamming GPS CRPAs no larger than the GPS FRPAs now used on military aircraft.
In its present form, the miniaturized GPS CRPA (see figure) includes a 6-in.- (15.2-cm)-diameter dielectric substrate with a ground plane on its inner surface, four rectangular microstrip patch antenna elements in a square array on its outer surface, and a superstrate (a dielectric lens) covering the antenna elements. The two elements on each side of the square are separated by half a dielectric wavelength (which is smaller than half a vacuum wavelength). The substrate material is chosen to have a permittivity large enough that the antenna elements can be made significantly smaller and significantly closer together than would be necessary if the dielectric were a vacuum. The permittivity and shape of the dielectric lens are chosen to minimize the mutual coupling between the antenna elements and to contribute to the overall reduction in size while enabling the array to exhibit the beam-forming or null-forming performance of a half-vacuum-wavelength antenna array.
The array is designed to be compatible with CRPA and GPS Antenna System 1 (GAS 1) electronic circuitry now used by the Department of Defense. In addition, the array is compatible with, and has been tested by use of, a high-gain advanced GPS receiver that includes a digital antenna- arraying subsystem that enables precise, digitally controlled beam-forming and null-forming. The test results confirmed that this miniaturized array performs, as desired, like a full-size CRPA.
This work was done by Alison Brown and Huan Wan Tseng of NAVSYS Corp. for the Naval Research Laboratory.
This Brief includes a Technical Support Package (TSP).
Miniaturized GPS Controlled-Reception-Pattern Antenna Array
(reference NRL-0015) is currently available for download from the TSP library.
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