Hello Experts!
What is meaning of Antenna gain in wireless devices in the sense that antenna is actually a passive device without any external power?
Anything between 1dBi and 17 dBi.
Not concerned with values.
Just trying to understand how antenna can amplify signal without any external power supply?
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That gain is not terms of power.
Generally an antenna is omni directional, but whenever you make it directional it shows gain since 1 major lobe is formed and rest lobes gets reduced.
In this sense we are calling it as gain.
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Ok… directional gain.
Thanks for clarifying. 
Gain in terms of an isotropic antenna, unit dBi.
Antenna does not amplify signal.
It is just that in some directions of space signal will sum up from multiple antenna elements adding it cumulative.constructively to a high signal whereas in other directions signals from different antenna elements will act destructively will not add up.
Kepp in mind that an antenna can have multiple elements (dipole usually).
Ok. In an omni directional antenna, antenna gain would be almost 0 dB, right?
Nope.
Isotropic has 0.
Omni still has some gains in some directions.
Try google it to find pattern of omni antenna.
Omnidirectional Atenna Radiation Pattern
Why Antenna have Gain while it’s Passive component?
Have you ever wondered why we talk about “gain” when referring to antennas, even though they are passive components?
Let’s explore the fascinating concept behind antenna gain and shed light on it.
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Antennas are essential elements in wireless communication, Microwave Transmission, satellite systems, radar technology, and so on. Antennas have ability to efficiently radiate electromagnetic energy.
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“Gain” is a term used to describe an antenna’s ability to concentrate or direct its radiated power in a specific direction. It measures the antenna’s efficiency in utilizing available power and focusing it towards a desired target or receiver.
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But wait, aren’t antennas passive components that do not actively amplify power? Absolutely! The gain of an antenna is achieved by effectively utilizing the available power and directing it in a specific direction, rather than actively amplifying it.
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The gain of an antenna is typically measured in decibels (dB) and is often referenced to an isotropic radiator or a reference antenna. An isotropic radiator is a theoretical antenna that radiates power equally in all directions, serving as a benchmark for comparing the directional properties of real antennas.
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Dish antennas that used in Microwave Transmission utilize a parabolic reflector to focus the electromagnetic energy in a narrow beam, resulting in increased signal strength and longer communication range
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. Stop Stop … Why larger dish antennas are associated with higher gain? So easy,The larger the diameter of a dish antenna, the larger the surface area available for capturing or radiating electromagnetic energy. This concentration of energy results in a narrower beamwidth and higher gain.
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So, the next time you hear about “gain” concerning antennas, remember that it signifies their ability to effectively direct or concentrate radiated power in a desired direction.
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