I designed planar circular monopole antenna . Its gain is 3.89 dBi and realized gain is also 3.89 dBi. Should there be difference of 10 dB in the values of Gain and Realized gain? Please guide
From the CST help page
Some Farfield Terms
Directivity: The directivity of an antenna is defined as "the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions." The radiation intensity is given by the total power radiated by the antenna divided by 4p:
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Gain: Accordingly, the gain is defined similarly but is related to the input or accepted power of the structure. In the case of a loss-free antenna (no conductional or dielectric losses), the gain is equal to the directivity. Note, that power flowing out any port is not considered as accepted by the structure.
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Realized Gain: The realized gain is defined by gain * (1 - Balance^2), it includes the impedance mismatch loss.
E-field pattern: The electric-field pattern provides a distance-independent characterization of the radiation pattern. It is directly related to the electric field evaluated using the farfield approximation:
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Due to its definition, the E-field pattern has the unit of a voltage.
Radiation efficiency: The antenna radiation efficiency is defined as the ratio of gain to directivity or equally the ratio between the radiated to accepted (input) power of the antenna:
📷 or 📷
Total efficiency: The total efficiency is defined as the ratio of radiated to stimulated power of the antenna:
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Compared to the input power, the stimulated power considers any occurring reflections at the feeding location.
Reflection efficiency: The reflection efficiency is defined as the ratio of input to stimulated power. Note that the input power is the accepted power, i.e. reflected power and power flowing out any port of the simulated structure are not included.
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It indicates a well matched input impedance. Do check the definitions of the antenna terms in IEEE Std 145 1993.
I expect the gain is the gain you get if none of the power into the antenna is reflected by an impedance mismatch. The realised gain is what you actually get with the actual mismatch. As Shiv Prasad Tripathy says, if the two are the same then there is no mismatch loss, so the antenna has been well matched.
Oh great. Thank you. So I donot need to amend my antenna to see if gain and realized gain has 10 dB difference.
Dear sir,
before coming in to conclusion, first we should understand the difference between two terminology ie gain of an antenna and Realized Gain of an antenna
1. Gain of an antenna : It refer to computation /evaluation of gain of particular antenna in idealistic condition, ie assuming 100% efficiency. 100% efficiency meaning there is no conductor loss, No mismatch loss, No contact loss and so on. THIS GAIN TERM ONLY CALCULATED THEORETICALLY ASSUMING THERE IS NO LOSS IN SYSTEM AS MENTIONED ABOVE.
2.Realized Gain of an antenna It refer to computation /evaluation of gain of particular antenna, taking into account losses due to reflections at the input terminals as well as losses within the structure of the antenna. In this case antenna efficiency is never be 100%, It is always less then 100%.
PRACTICALLY 100 % EFFICIENCY IS NOT REALIZABLE. THUS
GAIN OF AN ANTENNA AND REALIZED GAIN OF AN ANTENNA CAN NOT BE SAME.
Now for us both the terminology are clear. As mention by researcher Ms. Meenakshi Kohli, she got both the foresaid gain same that apper to be not appropiate . we need to look into it,
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Shrivastav a.k. I think you will find that in some prediction codes the gain is the calculated gain including the effect of losses. It is the gain calculated using the power that stayed in the input port. The realised gain is the gain taking account of input port mismatch, so is lower. Directivity is the correct term for the "gain" you describe. Directivity takes no account of antenna efficiency (except for aperture efficiency, which is not about lost power, but about aperture that was not used to the full extent it could have been to get maximum directivity).
Just to be more clear on this. These numbers I got from CST simulation. not from the actual antenna testing.
From the CST help page
Some Farfield Terms
Directivity: The directivity of an antenna is defined as "the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions." The radiation intensity is given by the total power radiated by the antenna divided by 4p:
📷
Gain: Accordingly, the gain is defined similarly but is related to the input or accepted power of the structure. In the case of a loss-free antenna (no conductional or dielectric losses), the gain is equal to the directivity. Note, that power flowing out any port is not considered as accepted by the structure.
📷
Realized Gain: The realized gain is defined by gain * (1 - Balance^2), it includes the impedance mismatch loss.
E-field pattern: The electric-field pattern provides a distance-independent characterization of the radiation pattern. It is directly related to the electric field evaluated using the farfield approximation:
📷
Due to its definition, the E-field pattern has the unit of a voltage.
Radiation efficiency: The antenna radiation efficiency is defined as the ratio of gain to directivity or equally the ratio between the radiated to accepted (input) power of the antenna:
📷 or 📷
Total efficiency: The total efficiency is defined as the ratio of radiated to stimulated power of the antenna:
📷
Compared to the input power, the stimulated power considers any occurring reflections at the feeding location.
Reflection efficiency: The reflection efficiency is defined as the ratio of input to stimulated power. Note that the input power is the accepted power, i.e. reflected power and power flowing out any port of the simulated structure are not included.
📷
Kindly go through to IEEE standards and clarify these things.I think there should be difference between them.
you may download it....
https://ieeexplore.ieee.org/document/286098/citations?tabFilter=patents#anchor-patent-citations
Realized gain is the antenna IEEE gain * losses. In your antenna case, if they are equal, it means your design has very low losses and the efficiencies should be very high. check the total efficiency.
The realised gain of an antenna is calculated by considering the total efficiency of the antenna, along with its directivity. The total efficiency of the antenna considers the losses due to reflections at the input terminals as well as losses within the structure of the antenna.
Read the definition I gave several posts ago from the CST help.
Whatever any other organisation defines the various gains to be, if you are using CST that is what they mean in CST.
No concept of 10dB difference. In simple way, the realised gain is what you actually get with the actual mismatch. It takes into account total antenna efficiency not radiation efficiency. Total efficiency includes material as well as mismatch losses. Probably your design has negligible losses? To confirm check input impedance variations as well as VSWR to assure less mismatch losses and to confirm conductor and dielectric losses, realization and measurement is necessary.
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