Calculating Radiation Resistance of a Loop Antenna

[AJ]

Hi,

I was just wondering if someone could help me out a bit. I have been
reading Microchips Application Note AN831 and it states that Rrad = 31171
*(A^2 / w^4), where A = loop area in square meters and w = wavelength. It
then goes on to say that and square loop with measuring 12 x 34mm at 434MHz
has a radiation resistance of 0.0227 Ohms. Can some one show me how that
works out??

Regards,


AJ

 

[Anthony Fremont]

Hi,

I was just wondering if someone could help me out a bit. I have been
reading Microchips Application Note AN831 and it states that Rrad =
31171 *(A^2 / w^4), where A = loop area in square meters and w =
wavelength. It then goes on to say that and square loop with
measuring 12 x 34mm at 434MHz has a radiation resistance of 0.0227
Ohms. Can some one show me how that works out??

w=wavelenth in meters
A=loop area in square meters

A= (.012*.034)
A=.000408 sq mtrs

w=300/434
w=.69124 mtrs

A^2 = .000000166464
w^4 = .22831

Rrad = 31171 * (.000000166464/.22831)
Rrad = .0227272101 Ohms

Looks ok to me.

 

[AJ]

w=wavelenth in meters
A=loop area in square meters

A= (.012*.034)
A=.000408 sq mtrs

w=300/434
w=.69124 mtrs

A^2 = .000000166464
w^4 = .22831

Rrad = 31171 * (.000000166464/.22831)
Rrad = .0227272101 Ohms

Looks ok to me.

Thanks Anthony... I cringe at my mistake