Find the directivity and efficiency of an antenna if its radiation resistance is 80 Ω, and loss resistance is 10 Ω. The power gain is 10 dB and antenna operate at a frequency 100 MHz.
efficiency= (radiation resistance)/total resistance=(radiation resistance)/(radiation resistance+loss resistance)
directivity=gain/efficiency in V/V units
directivity=gain - efiiciency in dB units
Beata Barteczka-Wilk
I'm not sure what you mean by V/V units, but it looks like a voltage ratio. Antenna gain is a power ratio, so is W/W or (V/V)^2, which is not the same as V/V (unless the V is the output from a square-law detector).
Antenna gain is not power gain. Amplifier gain may be referred to as power gain or voltage gain, but it is important to know which it is.
In the last messages, you have some equations to define this parameters of the antenna.
In short words, the directivity is the capacity of the antenna to concentrate the electromagnetic energy in one direction.
The efficiency is the ratio between the power emitted for the isotropic antenna respect to the input power in the antenna.
Greats
Dear Vigna Vundrajavarapu ,
You have at first to calculate the loss efficiency as
Eta loss= Rrad/ Rtotal= 80/90=
The directivity gain D. G.= 4 Pi / omega where omega is the radiation angle of the antenna.
The overall gain= D.G. x Eta loss
given that the power gain is 10 dB, then the overall gain = 10 dB
1o= 1o log G ratio
The gain ratio= 10,
Then the D.G.= 10/ (8/9) = 90/8=11.25
In dB= 10 log 11.25 = 10.51
Best wishes
Directivity of an antenna is the degree to which the radiation emitted is concentrated in a single direction. The directivity is defined as the ratio of the maximum signal strength radiated by the antenna to the signal strength radiated by the isotropic antenna.
Radiation Efficiency is the ratio of the total power radiated by an antenna to the net power accepted by the antenna from the connected transmitter.
Dear Vigna,
it clearly looks like a class exercise (:
I can't provide any better information than what other colleagues have provided, I hope your help has been valuable.
Best regards,
Refer to the following textbook which is considered as one of the most classsical and popular books on antenna:
Balanis, Constantine A. Antenna theory: analysis and design. John wiley & sons, 2015.
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