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A ground-plane antenna is a form of dipole antenna designed to work with an unbalanced feed line. A ground-plane antenna is more of less one half of the dipole and mounted above the ground plane. Ease of fabrication and cost makes the ground-plane antenna one of the popular antennas in communication systems.
A ground-plane antenna is also known as a monopole antenna.
A ground-plane antenna looks similar to coaxial antenna. The lower section of the antenna consists of two or more radials, which are straight elements. The radials measure ¼ of the wavelength and are connected to the shield of the feed line cable or to the outer connector. The main element that is used can be of any length, but is arranged to function in and around a specific frequency. This adjustment in the antenna is done with the help of a tuning coil. The main element is connected to the center conductor.
One feature of the ground-plane antenna is that it is omnidirectional. The horizontal radiation pattern is in the shape of a circle, and the antenna radiates in all directions and in equal measures. However, in the case of its vertical radiation pattern, it has a lower angle, unlike a dipole antenna. At frequencies below or around 50 MHz, this gives ground-plane antenna a longer range propagation advantage. In order to get a directional antenna with gain, an arrangement of two or more ground-plane vertical antennas can help. However, the ground-plane antenna has a narrow bandwidth.