Lossy Metal Vs Normal material type

Hello there,

I am a student researcher working RF specifically on patch and slot antennas! I have been following this forum for a while to gain knowledge and information and so far it has been a great source for me to understand RF. And, the active participation of various members made me create an account and be a part of the conversation.

So, I have been working of CST software to create designs and simulate them, as said mostly I have been working on patch and slot antennas. The question that I have in mind is, when should a material type be considered as lossy metal and when should it be considered as Normal, some threads were talking about points like skin depth vs the actual thickness depth of material. But, it would be greatly appreciated if anyone can give me some deep insight on this aspect. Please feel free to post any references or links for the material out there that can help me understand.

Thanks
Potter :)

In antennas it is natural to use good conductors like copper and aluminum, to reduce loss. Skin depth is an important parameter, the more as the frequency grows. Surface polishing is also important.

Lossy metals are generally not used as due to power dissipation, antenna power input will be limited. If your design needs to introduce certain lossy elements to shape the radiation pattern, it is easier to add absorbing bodies farther from antenna radiator.

Hello jiripolivka,

Thanks for your information. In my case, I am using copper as the patch and the ground plane. So, according to your post, I guess I have to go ahead with "Normal" type!..? And, can you help me understand about surface polishing can that be done using CST software?

Also, when you said shape the radiation pattern, in what cases, the need for radiation pattern shaping occurs?

Thanks,
Potter :)

Dear Potter:

I do not use software for microwave work. The best book I can recommend is by T.Moreno: Microwave Design Data issued in 1947 where details on surface polishing effects are described.
If you work on antennas, you will discover that the "calculated" and measured patterns differ mostly in side lobes. In practice it is difficult to correct the side lobes by regular design, in some sensitive cases designers use absorber patches located on reflectors, lenses or radomes and adjust their positions to reduce side lobes.