Loop Antenna Radiation Pattern 1

[ladyrose]

Hi all!
I'm designing a small circular loop antenna (single turn) in CST MWS.I'm just very confused about the radiation pattern i'm getting. I've been reading in textbooks that the radiation pattern of the loop antenna is like a dipole and must be in the plane of the antenna, i.e. the direction of the max radiation is NOT through the loop. But what i'm getting is the exact opposite.I've attached a printscreen of it in the pdf file below.

Also, to satisfy the small loop condition, I designed it so that its diameter is lambda/10: f=1GHz=>Lambda=300mm=>radius=15mm
but somehow the resonant frequency is at about 2.7GHz?

I tried increasing the dimensions, so that the resonant frequency is reduced.It did, but it never obeyed the lambda/10 rule(it was not what i expected to be). For example for a radius of 47mm, the resonant frequency is 875MHz.

Any help is greatly appreciated.

Cheers
pari

 

[VEBill]

"I've been reading in textbooks that the radiation pattern of the loop antenna is like a dipole..."

Similar, with differences.

"...and must be in the plane of the antenna, i.e. the direction of the max radiation is NOT through the loop."

Wrong.

Radiation from a loop is broadside to the loop, as shown in the screen capture. I don't see anything unusual in that regard.

Small loops are very common in low frequency DX'ing (e.g. trying to pick-up distant AM radio stations), and the loop is always facing the station, and edge-on to any interfering station that you might wish to null-out.

Are you interpreting the text book correctly? Or does it have a typo?

 

[hacksaw]

for the far field, assuming balanced excitation, the radiation field H vector (z-axis) is along the loop axis. The E vector is perp.

for what its worth

 

[Higgler]

per Jasik's Antenna Engineering handbook, for small loops, if you lay one flat on a table, there's a null upward and a null downward. Radiation is strong in the plane of the loop, or along the horizon for a loop lying flat on a table.

radiation pattern peak gain in a loop switches locations when you go from a large loop to a small loop.

make sure you look at electrically small loop radiation patterns.
k