antenna-theory.com

[wolberine]

I really enjoyed reading the Vivaldi antenna thought process and seeing how the author used intuition to design the antenna rather than equations.

I believe I have a decent understanding...

At 3.5GHz, the antenna is radiating similar to an IFA and at 5.5GHz, the antenna is radiating similar to a slot antenna. We taper the slot to increase antenna area, which typically increases bandwidth. We repeat the taper on the ground plane for a similar effect.

At 1GHz resonance, we see better VSWR because the impedance matching is getting better with tapering.

How would the curve of the taper change the characteristics? (ideas... concave vs convex curve or slower rate of change for the curve?)

Also is this method how antenna structures are designed for cell phones/consumer devices with high space constraints? Or is there much more simulation involved before a mock-up?

Thanks for reading!

[bigSteve]

By tapering the slot, we are reducing a lot of the capacitance that exists between the two halfs of the antenna. Bandwidth generally rises with decreased capacitance. THe total volume of the antenna is essentially the same.

Changing the taper speed would be a good study. It's tough to estimate, but if you taper extremely quickly you would just have the dipole mode. If you taper very slowly you would have the slot mode at the beginning of the page.

As for phones, different companies rely on simulation or mockups to different degrees. It ends up being a combination of the two - and a lot of experimentation.

http://www.antenna-theory.com/antennas/aperture/vivaldi.php