Wire antenna used as feed for reflector antenna [ku band]

[bukhari917]

Hello everyone!

I'm looking for an antenna that I have to use in my project.
I need a reflector antenna in Ku band which is being fed by a wire antenna.
Any one got any idea, any similar commercial product or any research paper on similar type of antena, please do let me know asap

Many thanks
Kamal

 

[saikat36]

Plz describe your specification more.
I think commercially such type of Antennas are not available.

 

[bukhari917]

I want to use any directional wire (probe/helical etc) antenna as a feed for 0.6m dish having focal length of 300 mm in the range of 11-14 Ghz. Reason behind using wire antenna is to reduce blocking as maximum as possible.

 

[saikat36]

I think this is very much professional task what do you want. An antenna design needs lots of parameter.

Best of luck

 

[jiripolivka]

Talking about a "wire" antenna to feed a parabolic dish at Ku-band is a technical nonsense.
First I recommend you to read a good textbook on antennas. There are many, like J.D.Kraus:Antennas, McGraw-Hill 1947.

Any parabolic dish must be correctly illuminated, for instance, by a primary feed antenna, to concentrate most of the energy into a narrow beam.
Such primary feed cannot be "a wire". Most often it is a horn antenna, or a dipole-reflector combination. The primary radiator must be designed so that its main lobe covers most of dish surface from the focal point where the primary radiator is located. Often the power density at dish rim is adjusted by design to be ~10-13 dB lower than at dish center.

Without the basic knowledge there is no way to talk more.

 

[chuckey]

As stated a parabolic dish turn a point source of RF into a parallel beam. You could get something to work such as a 1/4 wavelength aerial sitting in the base of a non parabolic shaped dish. One thing is certain it would contain a "hole" in the centre of its radiation pattern, the other that it would have to be designed and made as a one off and feeding the aerial would prove to be troublesome. That why no one bothers!
Frank

 

[bukhari917]

Talking about a "wire" antenna to feed a parabolic dish at Ku-band is a technical nonsense.
First I recommend you to read a good textbook on antennas. There are many, like J.D.Kraus:Antennas, McGraw-Hill 1947.

Any parabolic dish must be correctly illuminated, for instance, by a primary feed antenna, to concentrate most of the energy into a narrow beam.
Such primary feed cannot be "a wire". Most often it is a horn antenna, or a dipole-reflector combination. The primary radiator must be designed so that its main lobe covers most of dish surface from the focal point where the primary radiator is located. Often the power density at dish rim is adjusted by design to be ~10-13 dB lower than at dish center.

Without the basic knowledge there is no way to talk more.

Exactly you are right and thats actually a problem.actually the reason why i asked here was if there is some wire antenna (which probably is not in my knowledge) , which can give a directional gain which could be used as feed for reflector antenna.Indeed using a dipole or monopole or other such antennas would be a "technical nonsense" , so what i was asking is , do we have any other option at all?, i mean in wire antennas

---------- Post added at 09:25 ---------- Previous post was at 09:20 ----------

And i just got a random idea, can we use Biquad antenna for ku band??

 

[jiripolivka]

I tried to explain that feeding a parabolic-reflector antenna needs to use a good primary radiator , with a specific radiation pattern. A "wire" is not such radiator.

You can naturally scale down any antenna you can imagine, to Ku-band wavelength, ~2.5 cm. But another story is what is suitable to be used with a parabolic reflector, to get an optical system, with a useful radiation pattern- with a conical main lobe, and low side lobes.

You can naturally use a "bi-quad", and its radiation properties will remain the same as if you used it at 100 MHz. If you want to obtain a poor antenna system, you can use even a "wire".
But it is waste of effort and money, to put a bad primary feed in the focus of a good parabolic dish. The result will be technically a nonsense, but you can do whatever you want.

 

[bukhari917]

alright.thank you so much for the response. So would you suggest me any other type of directional radiator that will set fit with the above said dish (post#03), Actually we want to replace the horn with any other antenna.. :grin:
Fogive my blunders please :wink:

 

[jiripolivka]

If you do not like the horn, you can choose for other primary radiators. The important requirement is that any such primary radiator should be designed as an antenna with a radiator pattern matching the parabolic reflector. It means that the main lobe can illuminate the dish with a peak intensity at dish center, and -10..-13 dB at dish rim.
If you allow more at dish rim, you will loose by spillover. If you use a narrower main lobe, the dish area would be less used and the complete antenna will have a lower gain.

I advise again to find a good textbook on antenna design.

As a good primary radiator at Ku-band, you can use a dipole with a reflector like in earlier radars. A waveguide opening is also good due to its radiation pattern. The satellite LNBs are such "open waveguides", with choked rims to get the mentioned -10..-13 dB at dish rim. Such design seems to be almost optimal.