RAdiation Pattern Measurement

[pollop]

To all the experts

What is the difference between time and frequency domain procedure when measuring the radiation pattern of an antenna? How would you go about such a test and with what equipment?

 

[A.Anand Srinivasan]

antennas mainly have two parameters.... one is frequency of transmission and other is antenna gain.... the distance travelled and other things depend on the power of the wave....
the antenna gain almost entirely on frequency and hence the antenna gain can be analysed in frequency domain..... whereas the frequencies transmitted by the antenna at various instants of time can be plotted in time domain.....

 

[akedar]

normal;ly we do antenna measurements in frequency domain but when we are concerned with antennas with very wide or ultra wide bandwidths we have to chech teh signal dispersion aspect of it. Then we have to measure in time domain,i.e. measure spectral content of antenna with time

 

[pollop]

what can one interpret from the spectral content? Am i correct in thinking that the larger the amplitude of a particular spectral component in the TD, then that point is the best frequency to operate the antenna at?

 

[A.Anand Srinivasan]

you have to talk in terms of antenna gain when you decide whether it is best to transmit a particular frequency.... the spectral content would just show the amplitude of the signal transmitted or received at the particular frequency but not the power required by the system to transmit or how much usable info is got when received....

 

[beetro78]

When u talk about the spectral content you likely mean the aperture field spectrum, i.e. , the Fourier Transform of the aperture field. As you probably know this spectrum is related to the radiation pattern...practically IT IS the radiation pattern, unless a cosine term and the proper (u,v) -> (theta, phi) substitution.

Anyway, when you know the aperture spectrum you know essentially the directivity of the antenna...so..you know how it irradiates the power in to the space.

In coclusion, from the spectrum of the aperture fields, u can characterize almost completely the radiative behaviour of the antenna.

Bye