that's not true may be an antenna has two or four port
Agreed, but it is not usual. I can't think of any antenna designed for a single frequency where there will be more than one input port. For this particular design created by the HFSS antenna design kit, I have absolutely no idea how one is supposed to use it. If I had a GPS receiver for example, why would one connect it?[/QUOTE]
u can use antenna magus too for design
i attach some thing may be helpful for u
Thank you. Where did it come from? It looks interesting, but without the references, it is less useful than it might otherwise be. I find figure 22-8 confusing. The text "Centre connected to opposite element" is confusing to me. Whilst I can see where the antenna is fed from, where the coax first goes to the left, then then to the right, then goes left to the centre, at that point I'm confused exactly what is connected to what. I think the other part, despite being shown the same outside diameter as the coax, is in fact solid, and not coaxial. So the centre of the coax is fed to a straight piece of wire. At least that's what I think - I'm not 100% sure.
But note figure 22-8 only has a single feed point with coax.
As for figures 22-9 and the photo in 22-1, I really have no idea how the feed is arranged. The photograph does not (to me at least) provide any help on how the two loops are connected. It only shows to me there are two antennas, one a big bit bigger than the other, and their size is quite small compared to a pen.
The design I posted was not created by Antenna Magus, which is an expensive commercial product. (I have seen a copy, and thought it of limited value, as it is too inflexible to be of much use. I'm amazed they manage to sell Antenna Magus. The design I posted was crated by the Antenna Design kit for HFSS, which is a free download if you have HFSS. In fact, if you don't have HFSS installed, the product will not install itself. What I see in HFSS is 16 S parameters. S11, S22, S33 and S44 are such the return loss is good on each. But it's not clear to me how you excite these 4 ports such that the return loss remains good and it has a decent radiation pattern. Clearly if you excite port 1, whilst ports 2, 3 and 4 are terminated in 50 Ohms, the return loss at port 1 will be good. But if you excite two ports, then that wont necessarily be so, and you need to have some idea on how to excite them (phase relationship between them). None of that is clear from the antenna design kit.
Deborah