Looking for information about the feeder of offset dish

[cbsirio]

Offset Dish Feeder

Hi all,
I was searching for information (links, books, publications, suggestions) about the dimensioning of a feeder for dish antennas.

My goal is to achieve a feeder for 5.7 GHz band (I am radio amateur), and realize it with lathe or mill :twisted: .

Can someone help me, please?

I searched on Google, but with no success, and asked to my friends, but no one know anything about it...
The only sure thing is that the feeder for normal dish is different from the offset dish... Why?! How can I design it?! which rule shall I follow? Which simulator is better?

Many thanks to all !!

Ciao, Sirio.

 

[flatulent]

Re: Offset Dish Feeder

You will be better off with a center feed. There will be some blockage by the feed, but you can use an ordinary parabola reflector and an ordinary directive feed horn or patch antenna.

It is best to put the TX power amplifier and the RX first amplifier stage right at the feed. Even better is to put the entire transmitter and receiver there and run the base band signals and power on ordinary small diameter coax and cables.

Offset feed requires very special reflector shapes and feed radiation pattern shapes.

 

[cbsirio]

Re: Offset Dish Feeder

Hi flatulent,

I agree with you: with ordinary dish is all simpler...

...but I am also a future (I hope ) telecommunication engineer, so I am very interested to understand how it works! :wink:

I have also done the "antennas" exam, but no references to offset dish antennas...

So, Can you (or someone else ) help me to find how is the feed radiation pattern shapes? and the theory that is behind it ?!

Many thans in advance!!!

Ciao from Italy!

Sirio.

 

[eirp]

Re: Offset Dish Feeder

You mean something like the antenna in attachment?
It's offset dish for 2.45GHz with ~ 21dBi gain, simulated with CST MWS and results proved with measurement.

 

[vfone]

Re: Offset Dish Feeder

Try this
http://www.w1ghz.org/10g/5760.htm

 

[plasma]

Re: Offset Dish Feeder

Hi cbsirio

look at this link
https://www.ticra.com/
https://www.ticra.com/newrel.htm

You will find what you are looking for

PL

 

[cbsirio]

Re: Offset Dish Feeder

Hi Eirp!

Yes! My goal is this!...
Build an illuminator for an offset dish and simulate it before machining it!

But, what are the important things to know?!

I explain:
I sit down to my chair... and then?! :?

what are the line guides to achieve my goal?! I have to calculate ... what?

I have a dish, all phisical dimensions, the focus, and the frequency where I want to transmit(and receive, of course)...

I have some mathematics (Maxwell equations :x ) and then?! I have to build my illuminator, I think I should corrugate it to reduce the spillover, but which shape have I obtain?
Have I to start from a circular horn? but if the dish is offset, is the same ?!

I haven't done it first, so I didn't know from where to start!

Can you help me?!
Any suggestion is welcome, Books, Publications, internet sites... I really want to learn, so every information, hint, faq, (or think to other :sm18: ) is very welcome!

Many thanks to all!

Ciao from Italy

Sirio

 

[cbsirio]

Re: Offset Dish Feeder

Hi Plasma!

I have just seen your link and it seems very interesting!

I found 2 pdf of 300 pages... 8O Urka!

Ok, I'm going to read them :sm34: : I hope to find what I was searching for!


Thank you very much!!

Ciao from Italy

Sirio

 

[plasma]

Re: Offset Dish Feeder

Hi cbsirio

Ticra code is one of the best in the reflector antenna
so just read the pdf file and then download the demo
ver. I hope it will help you to start.
It’s not user friendly as cst but if you buy it. I think
You will get a course.
Try to give them the specification, and they maybe will deliver you the
shape and the exact feeder to build your antenna. Just ask
them.

PL

 

[cbsirio]

Re: Offset Dish Feeder

Hi Plasma,

I cannot buy it: I am "only" a student and a technician, I haven't so much money to spend...

I want to understand this, but this isn't a work (for now).

Of course, I want this because if in the future, for work, I will need to build an illuminator, I will not ask to Osram or Philips for a 100w bulb! :lol:

But, do you think they will answer to me? to a student? :roll:

Thank you very much again!!!

Ciao! Sirio

 

[plasma]

Re: Offset Dish Feeder

Hi cbsirio

I am sure they will answer you because students are
the future buyers for their products. So they make “sv”
Student Version. you can download it there.
In general, most of the companies give the code for
free to universities as investment. So try to get it thru
the university. For free.

PL