Microstrip patch antennas for GPS applications

The authors describe the preliminary designs of two different types of microstrip antennas, i.e., those providing dual-frequency circularly-polarized (CP) operation; and enhanced low-angle radiation. The first type of antennas was designed to operate at the GPS (Global Positioning System) frequencies of 1.227 and 1.575 GHz, and was fabricated by using a novel combination of recessed cavity and patch type of resonators. For the second type of antenna, achieving enhanced gain at lower angles without sacrificing the CP performance turned out to be a difficult challenge. After many unsuccessful attempts, a preliminary design that employed a pyramidal configuration appeared to exhibit good promise and favorable potential for further improvement.<
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