antenna measurements - radiation pattern and gain

[per_lube]

Hi,

got few question on antenna measurements...

To measure the radiation patterns and gain of an antenna is it necessary to have an antenna with a known gain?

Can't we use two identical antennas (say two antennas to be tested) to calculate the gain and obtain the radiation pattern?

In laboratories I've seen they use a wideband reference antenna... Is it necessary to have such wideband for the reference antenna?
Or is it enough to have the operating frequency band of the DUT in the reference ant?


cheers,
per_lube

 

[Joel-Tang]

Yes, a known reference is needed but only at the frequencies you intend to measure.

I suppose if you had two antennas that are exactly alike, you could make a single point to point far field measurement in ideal conditions (no Fresnel interference, not very humid with dry soil if outdoors).
Then in dBs calculate: 'calculated loss' - 'measured loss' / 2 = 'Antenna gain'
This would give you one calibrated point you could then use to measure your Antenna. So long as Characterized point of the measurement antenna is facing the Antenna under test for every point measured.

Another method is to use a known gain antenna like a 1/4 wave monopole or a dipole antenna. They are easy to make with some solid copper wire. Just take care that you are using the right portion of the pattern of these antennas for your actual measurement or you will get the wrong answer.

I hope this helps.

Joel Richard