What is the purpose of a ground plane on a GPS antenna?

• A. To improve mechanical stability
• B. To increase gain
• C. To filter out low-frequency interference
• D. The ground plane reduces interference from reflected signals

Answer: (D)

The ground plane provides a stable RF reference that shapes the antenna’s radiation pattern and impedance, which is essential for reliable GPS reception. Acting as a conductive mirror, it works with the feed to form an effective radiator that directs more energy toward the sky and stabilizes the impedance, leading to better signal strength and consistency.

This setup also helps minimize the impact of signals reflecting from the mounting surface or nearby structures. By creating a controlled reference plane, the antenna becomes less sensitive to unwanted multipath from reflections, so interference from those reflected signals is reduced rather than amplified.

It isn’t primarily about mechanical stability, filtering low-frequency noise, or simply increasing gain by itself; the main role is providing a proper RF reference that improves the directional pattern and reduces interference from unwanted reflections.