10dB and 20dB Horn Antenna

[winsonwhy]

Hi friends, :smile:

Anybody know what are the differences between the 10dB horn antenna and the 20dB horn antenna?

I am just a beginner in horn antenna stuff. I saw many company they are selling this two type of horn antenna.

Somebody mind to share their knowledge on this?

Thanks in advance!

 

[jiripolivka]

Hello there:

as you can see, the difference between the two is 10 dB. I would recommend you to read a basic textbook on microwave antennas to learn important details.
Horn gain is directly linked with beam width- so the higher the gain, the narrower the beam.

 

[winsonwhy]

Thanks for explain.

So which one of them is more suitable for use in design of reflectarray as the feed horn antenna?

Any suggestion will be appreciate.
Thanks again.

 

[biff44]

If used in front of a receiver, the 20 dB horn antenna will give a received signal that is 10 dB higher, maybe giving you 2-3 times the range. You also will be less bothered by interference from other sources.

HOWEVER, you will have to carefully point the antenna at the transmitter, as the spot size of the antenna will be very small. With the 10 dB antenna, you will have 10 dB less received power, but can be much more sloppy about where you point the antenna.

 

[jiripolivka]

To feed any antenna including a reflectarray, primary-horn gain is not important.
What is important is that the primary horn should irradiate the active area of a reflector or your reflectarray in an optimum manner.
To irradiate parabolic reflector, the primary radiator (horn) is designed so that its radiation pattern covers the surface while the intensity should drop to < 1/10 on the rim. A similar rule holds for other antennas. Horn aperture size is designed to form the beam.

This geometry should guarantee that the rear radiation is low as well as the sidelobes of the complete antenna.
Again, your questions indicate that you have no knowledge of antenna design. A recommended textbook is : Kraus, J.D.:Antennas. There are many others, too.

 

[Azulykit]

There will also be a significant difference in the physical size.

Do some research and post your findings.

 

[winsonwhy]

Thanks everybody for reply,

Azulykit you are correct, higher gain will have larger size.
**broken link removed**

 

[cnm]

Gain is related to effective radiation aperture area. Higher gain has a bigger aperture size. Then better directivity and narrower beam width, as said in posts above.

 

[RCinFLA]

Thanks for explain.

So which one of them is more suitable for use in design of reflectarray as the feed horn antenna?

Any suggestion will be appreciate.
Thanks again.

I assume you mean as a feed for an antenna such as a parabolic reflector. You need to consider the illumination of the reflective surface. Too narrow a feed beamwidth will concentrate radiation in center of reflector and not achieve the full gain potential of the reflector.

Too wide a feed beamwidth will have spillover, again reducing gain.

There is also sidelobe consideration. Uniform illumination of a reflective surface will generates significant sidelobes of overall antenna.

These sidelobes can have negative effect on antenna noise temperature for space and radio astronomy considerations because they look at relatively hot earth.

Then there is the X and Y symetry, or E plane/H plane, consideration. Most horn feeds from rectangular waveguide have an oval pattern of illumination. Circular scalar choke feeds give better E/H plane symetry then a rectangular horn feed.

Illumination of reflector is like Fourier series analysis. Tapered illumination will reduce sidelobes, at expense of some gain. Since the name of the game in reception is usually signal to noise ratio, this reduced sidelobes may reduce noise and therefore end up better S/N even though gain of antenna is reduced.

 

[winsonwhy]

There is also sidelobe consideration. Uniform illumination of a reflective surface will generates significant sidelobes of overall antenna....

Illumination of reflector is like Fourier series analysis. Tapered illumination will reduce sidelobes, at expense of some gain. Since the name of the game in reception....

What kind of illumination that a rectangular horn antenna provide? Is the uniform illumination or the tapered illumination?

 

[RCinFLA]

What kind of illumination that a rectangular horn antenna provide? Is the uniform illumination or the tapered illumination?

Any real antenna have tapered response, only variation in the rate of taper. You can look up a given horn at a given frequency as its response changes with frequency. For a TE10 mode rectangular waveguide horn the E-plane and H-plane radiation patterns are slightly different, both having an oval pattern. Pattern is also dependant on flare rate (E & H plane) on pyramidal horn.

You can use any illumination spread. Generally a -5 db to -10 db horn beamwidth is used for reflector edge illumination depending on how much sidelobe suppression is desired.

 

[Azulykit]

The first order answer to the illumination taper in a pyramidal horn is that it is uniform in the H plane and cosine tapered in the E plane. Length of flare plays into the mix but I have ignored that reality.

One generally sees lower E plane sidelobes because of the taper relative to the uniform H plane aperture illumination.

I am also assuming that the horn is fed with a rectangular waveguide operating in it's fundamental mode. Nothing fancy in the horn. Run down a copy of Kraus or Silver to read about horns. Lots of antenna books have chapters on the subject.