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14th October 2015, 17:23 #1
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received power in dipole antenna ?
i designed a wire dipole antenna in FEKO and simulated it . i found it directivity by using the equation
Directivity = 2/(cosθ1cosθ2) . θ1,θ2 are the 3db points of elevation plane of the dipole antenna. i got θ1 as 51.6 degree and θ2 as 128.6 degree hence my directivity becomes 1.6129 dbi. i found the aperture of the dipole antenna from the equation Ae = D*λ˛/4*pi i got Ae as 0.5134 (my frequency is 74.9481 Mhz ). i constructed two equal dipole antenna in FEKO . i placed two dipole antenna 2 Meter apart . the first dipole is feed by 1 V 50 Ohm voltage source so i calculated the transmitted power by the equation Ptx = V˛/R i got it as 0.02 watt. i calculated the received power in the second antenna by the equation Pr =Pt*Gt*Ae/4pi*r˛ my i got Gt above (i took Gt and Directivity are same) calculation as 1.6129 dbi , r= 2 meter then i got Pr =0.000328 i converted in to db as 10*log(p2/p1) i got S12 as 17 db. but i got S12 in FEKO as 14.28 Db.
is my calculations wrong? if it wrong how can i calculate the received power in the second dipole antenna theoretically ?? why there is more than 2 db difference in calculations ??[IMG]http://www.elektroda.pl/cgibin/mimetex/mimetex.cgi?3$%5Cnabla[/IMG]

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14th October 2015, 18:22 #2
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Re: received power in dipole antenna ?
The quoted equation is only valid in far field, 2 m is clearly near field. That's at least one possible explanation for deviation.
For a more exact caluculation of transmission in near field, refer to antenna theory text books, e.g. Balanis.
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15th October 2015, 03:34 #3
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Re: received power in dipole antenna ?
[QUOTE=FvM;1474244]The quoted equation is only valid in far field, 2 m is clearly near field. That's at least one possible explanation for deviation.
................... [QUOTE]
yup, agreed
any power transfer (induced currents) within nearfield is more akin to a transformer primary and secondary windings or a 2 parallel conductors situation
Dave
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15th October 2015, 05:20 #4
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15th October 2015, 15:47 #5
 Join Date
 Apr 2013
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Re: received power in dipole antenna ?
i increased the distance between them by 10 meter. then i got s12 as 31.80 db and i got 26.78 db in feko
there is approximately 6 db difference. is my equations correct??? did i missed anything??[IMG]http://www.elektroda.pl/cgibin/mimetex/mimetex.cgi?3$%5Cnabla[/IMG]
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