# antenna question...

#### MilK

Joined Mar 1, 2008
25
hi,

need some help answering some antenna questions...

2 isotropic radiators at x = -d and x = +d on the horizontal x-y plane. for primary radiation lobes to be in +/- y directions, the radiators are fed by 100Mhz sources having equal amplitudes with no phase difference.

1) a strong signal is arriving from distant radar station at φ = 60 deg.( φ is angle with x-axis). find value of d for minimize interference posed by distant radar station.

2)determine the power levels in the side lobes(if any) relative to the power in each primary lobe.

3)the 2 isotropic radiators are replace with 2 half-dipoles(with their axes vertical to x-y plane) does the result of part 1 & @ need to be re-computed?

#### oldschoolcivic

Joined Mar 23, 2010
4
"2 isotropic radiators at x = -d and x = +d on the horizontal x-y plane. for primary radiation lobes to be in +/- y directions, the radiators are fed by 100Mhz sources having equal amplitudes with no phase difference. "

"1) a strong signal is arriving from distant radar station at φ = 60 deg.( φ is angle with x-axis). find value of d for minimize interference posed by distant radar station. "

I get 5.98m using a freq of 100Mhz

"2)determine the power levels in the side lobes(if any) relative to the power in each primary lobe."

Well technically if the antennas are isotropic they propagate in all direction equally. So in the xy plane it would look like a dipole. So I believe there would be no sidelobes, but I could be wrong.

"3)the 2 isotropic radiators are replace with 2 half-dipoles(with their axes vertical to x-y plane) does the result of part 1 & @ need to be re-computed? "

Here we could imagine that each dipole radiation looks something like a doughnut but viewing from up above so I would say that we can assume the previous estimation is good.

Hope this is correct