Hello Nitin Mehta ,

The following article may aid your cause. Good luck!

Article Analysis of graphene based miniaturized terahertz patch ante...

Thank You Md Abdul Kaium Khan for the suggestion. I'll definitely check the article.

Your designs look like spirals in which case they should be wideband. If they are indeed spirals they would support circular polarisation. The two spirals seem to be fed in phase and they spiral in opposite directions so one would be left-handed and the other right-handed, giving a resultant field that is linearly polarised. I would suggest copper metallisation (typically half-ounce copper) on a low permittivity substrate and no metallisation on the reverse side. The low permittivity substrate promotes effective radiation. I would then allow an air-gap to a metallic reflector such that the total electrical distance to the reflector is a quarter wavelength (e.g. at a mid-band frequency). The reflector would permit radiation in only the forward facing hemisphere but would double the gain in the forward hemisphere c.f. radiation over a full sphere. I have found the use of a wide air-gap (or foam dielectric) important in achieving wideband operation. You can play with the structure in CST to obtain the bandwidth and radiation pattern you require.

You seem to have a microstrip feed. A microstrip feed would require metalisation on the lower side and would also benefit from using a higher permittivity dielectric. So your feed and radiative elements could well use different materials.

Hope this helps.

Thanks Clive Alabaster

Your answer really provided great understanding for my design. I'll definitely keep in mind all the points while designing the antenna.

Since you said the spiral design will provide wideband operation but is there any way to make it multiband while keeping the same base design of spiral but adding or subtracting some extra design ?

@ Nitin Mehta

I don't know of a way to make a multiband spiral antenna, apart from using several different spirals. Spirals are inherently so wide band that multiband operation is really rather unnecessary. There are plenty of ways of making more classic patch antennas multiband, such as using parasitic elements resonant at the other frequencies you require. A spiral is actually frequency independent (in theory) but practical limitations might restrict you to a decade bandwidth, typically. I recommend the book "Antenna Theory Analysis and Design" by C. A. Balanis. I've always found that it is matching a good feed network to spirals to be the main challenge, so if modelling the antenna in CST, I would suggest you also include the feed in the model.

Thank You Clive Alabaster for the answer,

I'll definitely read the book and design the antenna accordingly.

For the implementing the patches you can use the standard materials thought for them. If you work at relatively low frequencies, then you can use the FR4 PCB material. If you work at higher frequencies you can use Roger substrates. At much higher frequencies you can use Teflon substrates.

To design multi band frequencies please refer to the paper in the link:Article Design of a Planar MIMO Antenna for LTE-Advanced

Abdelhalim abdelnaby Zekry Thankyou for the recommendation. I guess I'll go with the FR4 substrate.