Re: bow-tie antenna hfss
this post is old but if possible plz can u guide me for bow tie,i am trying to simulate cross bow tie antenna but its s para metesrs comes to be -.12 db onle and impedance is real part is zero and imginary part is 50 ohm,should i increase thickness of substrate?
QUOTE=heedavid;448467]To chamonz,
I've written something about the bow-tie antennas in other threads, but I won't mind re-iterating myself again!
After reading your post, I sorta understood what you're trying to say. So, we shall just constrain ourselves to a bow-tie DIPOLE etched on a substrate (hence, the 'patch' term you've used):
A bow-tie structure is inherently BROADBAND. To me, as long as anything that has a bandwidth of more than the conventional 10% - 15% (e.g. patch antenna) is broadband. But of course, if you're comparing to UWB antennas, definately it will seem 'narrowband' to you!
So now considering a dipole structure over a ground plane, the usual lambda/4 objective still pertains. BUT, you can reduce that dipole-to-ground spacing with a suitable material. Now when that happens, the usual microstrip patch antenna analysis comes in. Of course, trade-offs also occurs, so you must be careful.
Now, on the other hand without proper design, when you place any scattering/radiating structure too close to the ground plane (e.g. in this case, maybe a commercially-off-the-shelf FR4 PCB thickness depth), you'll run the risk of 'shorting' it out. This could explain your "problem that the impedance, both real and imaginary, are almost zero". Your design probably shorted out certain modes of operation.
And for "about the space between two triangular patches", as long as it is no wider than lambda/4 to your designed half-wavelength bow-tie's fundamental operating frequency will do. Even having said that, I don't think there really is a 'specific' formula. And yes, I would recommend a parametric study on the spacing to see which suit you better. Would any readers care to comment?
I hope these helps,
Dave[/QUOTE]