Help me simulate spiral antenna with NEC code

时间：03-23 整理：3721RD 点击：

Dear friends!

I need to simulate spiral antenna with NEC code.
I don't work with NEC usually but now I need to analyze the spiral antenna for very low fq (~20MHz) and IE3D seems not working properly there.

Please look in attachment how it should look.. I'd be happy for only just the spiral definition (without the violet bridge). I understand it will be composed from wires only but it's OK for my purpose.

Who can post sample file here, how to build it - include the source? Then I'll adapt it for my requirements myself.

I'm new in NEC and no time to study the input file

Thanks a lot for help

eirp

Dear eirp,

Why don't you use CST MWS? What about Agilent Momentum?

Regards

Dear wave-maniac!

Thanks but...

the spiral has diameter ~8cm (not my requirements!!) and f~20MHz.
In MWS you have very small structure and the PML should be at least lambda/4 away from the spiral --> very big calculation domain and meshing problems!

Momentum - probably the same as IE3D, not reliable results for such low frequency.

I've decided to try NEC then :)

You're right marti!

And that's why I need the input file for spiral in NEC..
IE3D also sucks on such low fq
Who works in NEC please???

i used a code named AWAS to simulate a logperiodic antenna. i know that a software package named super-nec (integrating with matlab) is also a nice NEC code. try it, supernec 1 is free (ver. 2 is not!). this is a helica antenna or what? u just want to know NEC code for a spiral? FEKO user manual have a very good NEC help. i will post you if you want just it.

marti

Dear eirp,

you didnt mention nothing about exciting/feeding the spiral antenna. If this is something of common knowledge, sorry for my ignorance...

Anyway, in just a few minutes I've managed to draw this structure in supernec. The wire segments are entered as x1,y1,z1 x2,y2,z2 .... no problem at all to draw your structure by this way. But feeding part i havent figured out yet :?

Dear rfmw,

thanks for valuable reply.
The feeding should be between 2 ends of the spiral (they will be connected with another wire) - that's not supposed to be a major problem.

More important is that I need circular spiral and I need to control its parameters easily (number of turns, spacing etc..). So I'd appreciate better some script to generate nec file??!

TNX mate

eirp

I see, so it should look like this? :D

I'll try to figure something out, how to draw the structure simplier

see ya ;)
rfmw

"More important is that I need circular spiral and I need to control its parameters easily (number of turns, spacing etc..). So I'd appreciate better some script to generate nec file??! "

a (stupid perhaps) way do do this is to program a C or Matlab file that outputs wire coordinates and has the input parameters that you desire..

regards,
rfmw

one, very similar structure like yours, exists in supernec and its called coniclogspiral antenna.

it has 2 or 4 arms (yours only 1) and it has height (yours doesnt and looks flat in your picture above)

...but... :D

the matlab file, which describes it, has all the trigonometrics equations required to output coordinates of wire segments from the input parameters at the picture bellow.

look at the attached .m file for this equations

hope any of this helps :)

best wishes,
rfmw

Thanks all for suggestions!

Finally I've make a piece of ugly code in matlab which creates the structure and calls snec 8)

It's nice and powerfull engine!

cu

eirp