question about radiation pattern quick analysis
For a given frequency and antenna dimension (aperture), what is the general radiation pattern looks like? I remember the max. gain can be calculate as:
G=4*pi*A/(lambda)^2, which A is the aperture size, and lambda is the wavelength.
But how about other parameters, just like beam angle and side-lobe level? Are there any general rules of thumb for that?
And are there any quick antenna computer program or formula to calculate the radiation patterns for horn antenna or reflector antenna vs. the dimension?
Since that's only the prelim study, the full-wave EM software is too time consuming...
Any recommendations are welcome. Thanks.
There are general rules for pattern shape.
Kraus and Silver's books go into detail. Beamwidth is on the order of 70 deg / (aperiture dimension/wavelength). Wider the aperture, the narrower the beam. Introduction to Airborne, Stimpson is another deceptively useful reference.
You might also like: gain = 10 log (42000/(Θ*Θ)) where the angles are -3 dB beamwidths in degrees. Gain in this case is actually "directivity".
Sidelobe level depends upon the aperture taper, the more the taper the lower the sidelobe level. A uniform aperture is 13.2 dB down and a cosine taper is around -17 dB down for a rectangular aperture. Silver has interesting tables on this subject, pg 192 and vicinity. I just look for the dirty page edge on my book.
Pattern main beam shapes can be approximated as cosine to a power (higher the power the sharper the beam). Cosine raised to 1.7 is often pretty good. A parabola shape is pretty good too as one can often match 3 and 10 dB beamwidths fairly well.
Scientific Atlanta/ M I Technologies used to hand out paper sliderules with these approximations on them. I don't know if they still have them available but you might want to ask. I have seen similar calculators from Daytron and Andrew.
I know this response is likely to start a "discussion" about how this set of "rules of thumb" is no good and that one should use some other set. I apologize for putting the wrong set up in the first place and concede that what ever someone else likes is the better choice. Take that as a given. Look at the references and come to your own conclusions.