The radiation pattern of a GNSS antenna is defined by the antenna’s capacity to radiate or receive signal power in different directions. This pattern directly affects signal quality and positioning accuracy. GNSS antennas are engineered to receive signals from satellites across the sky.
Firstly, the ideal GNSS antenna has an omnidirectional radiation pattern in the azimuth plane. This ensures uniform sensitivity across all horizontal directions. It also features a hemispherical pattern in the elevation plane to cover the visible sky.
The next stage is for the antenna to receive weak satellite signals from high elevation angles to the horizon. Therefore, it must provide strong gain towards the zenith. This helps to maximise signal strength from satellites in direct overhead position. However, it is important to note that gain typically decreases at lower elevation angles. Designers control this trade-off to reduce reception of unwanted signals. Please be aware that signals reflected from buildings or the ground can cause multipath errors. Antennae with reduced gain at the horizon can assist in the rejection of these reflections.
Additionally, the antenna’s ground plane plays a critical role. This has a significant impact on the radiation pattern, with the result that downward signal reception is suppressed. A well-designed ground plane has been shown to improve pattern symmetry and reduce signal distortion.
Furthermore, qualified professionals frequently use choke ring and patch antennas in precision GNSS applications. These antennas provide stable radiation patterns and reduce multipath interference. Tests show they maintain consistent gain across various elevation angles. It is imperative to ensure the stability of the radiation pattern to facilitate precise phase measurements. Any distortion or asymmetry can introduce bias in position estimation. Therefore, high-precision GNSS receivers use calibrated antennas with known radiation characteristics.
Real-world applications
In dynamic environments, the consistency of the radiation pattern is essential for reliable tracking. For instance, in the context of UAVs or mobile platforms, stable patterns are key to minimising signal dropouts.
In land surveying and geodesy, antennas with stable patterns help get centimeter-level accuracy. UAVs need antennas that keep tracking satellites during fast turns and movements. In farming, machines use antennas with wide coverage to stay accurate near the horizon.
On ships, antennas reduce signal reflections from the water. Aircraft need antennas that receive strong signals from satellites overhead.
Timing stations use stable patterns to keep telecom and power networks in sync. Self-driving cars rely on even coverage to avoid signal loss in cities.
Military systems use special antenna patterns to block jamming and focus on satellite signals. In all these cases, the antenna’s pattern helps keep signals strong, reduce errors, and improve GNSS accuracy in different environments.