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How exactly a ground plane helps inproving antenna gain? What is the logic behind it?

As per my general understanding, ground plane in reference to any perticular signal trace on PCB helps to absorb unwanted radations. Hence reducing radiated noise.

But in case of a antenna as it is a radiating element, how a ground plane works in other way.

A also heard about ground plane works as a reflector for antennas. Need to know more about it.

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In microstrip patch antennas, a radiating patch sits above a substrate and below the substrate there is a ground plane. The ground plane is used for directing the electromagnetic energy in the forward direction. The ground plane is a conductor and metals reflect electromagnetic radiation. Usually, a copper is used as a ground plane with thickness of 35 micron. Some antennas are designed with etched ground plane. If you have an antenna with ground plane (microstrip antenna) and without ground plane (sometimes called monopole), the antenna with ground plane provides more gain than the one without ground. Whether to include ground or not depends on the application and radiation characteristics requirements.

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The diopole is the mother of all antennas and all other antennas are merely adoptions of the dipole. A dipole consists of two wires pointing away from each other and the electrical field between these wires are generating the radio waves. This is the basis of all other antennas, you need to generate an electrical field to generate radio waves and as with electrical potential you need a reference point.

As the radio waves are generated by the electrical field between the antenna and the reference, try imagine the field between the two wires in the dipole antenna, that has a quite uniform gain pattern. Now replace one of the wires with an electrical conducting plane that is not small in relation to the wavelength of the radio waves, and imagine the electrical field generated and how this would affect the gain pattern of the antenna.

The above is merely a thought experiment to get hold of the general idea of how antennas work but with a lot of simplifications and generalizations.

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