Chapter 9GNSS Receiver Antennas

The receiver antenna is the first block in a chain of signal transformations to convert the signals emitted by the satellites into useful data. Some of the antenna features define the currently achievable accuracy of positioning. However, traditionally, the basics of applied electromagnetics are omitted in courses on satellite geodesy. To compensate for that, the first six sections address fundamentals of the electromagnetic field and antenna theory with focus on antennas useful for precise positioning.

In Section 9.1, plane and spherical electromagnetic waves of different types of polarization are discussed and widely used reference sources of radiation—a Hertzian and a half-wave dipole—are introduced. This allows treating the radiation of any practical antenna as interference of radiation of Hertzian dipoles, and in doing so, coming to a unified field representation that is valid for any arbitrary antenna. In addition, the widely used complex notation for time harmonic signals and dB scale are explained is this section.

Section 9.2 discusses antenna directivity and gain. The discussions on antenna pattern are supplemented with examples of a perfect antenna for satellite positioning, base station antennas, and rover antennas. It is shown that the cause of the largest error in regard to positioning is the conflict between antenna gain for low elevation satellites and the ability of an antenna to suppress multipath reflections associated with these ...

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