I want to design the curve of vivaldi antenna but am not able to do it exactly. Also I am not sure about the equations required for designing. I want to know on which parameter does its resonant frequency depend?
Vivaldi is a UWB end-fire antenna. Resonance appears only at very low frequencies where the antenna resembles a small dipole, but those frequencies are beyond its normal frequency range of operation. The antenna gain depends mostly on the ratio length/wavelength, the lowest frequency - on the width of the opening. The frequency band is limited usually also by the used balun. Perhaps a transient solver as e.g. CST Microwave Studio is better for UWB antennas like Vivaldi.
Thanx Valeri... U mean to say that if i want to design a vivaldi antenna at particular frequency, i should adjust the width of the opening accordingly?
Also, is it necessary that vivaldi antenna is UWB?
Vivaldi is the antenna built as widening slotline. It is in fact a long steep transition from slotline to free space, thus it is necessarily UWB as any long steep transition of transmission line. So, for the single frequency operation a patch antenna is more reasonable as it is low-profile. However, patch antenna has also usually low gain. Vivaldi antenna occupies much more space (it is long) but provides higher gain.
Antenna width W can be equal to one wavelength. But it will radiate also waves with the wavelength from 2W to 0.5W and even shorter depending on the used balun.
Length of the antenna can be limited to 2 wavelengths, if longer - the gain will grow.
I think U can look into "Modern antenna handbook" 2008 by Balanis or ch_8 in Handbook by Volakis and also Vivaldi is not a single resonance design.
vivaldi antenan is a traveling wave antenna ie non-resonant antenna...it operates over a band with similar char all over it. Check paper by Schaubert on it
Basically Vivaldi is an End-FIre antenna. Use antenna design kit from HFSS to design vivaldi for and frequency band. But if the vivaldi requirement is for an array or conformal its a different game. The most important is HFSS has issues when solving large arrays cause of its FEM engine. I suggest FDTD is better in case of Arrays. FEM fails when it tries to invert the large matrix generated from the arrays (green function). Since vivaldi is not ground plane backed the performance degrades and we can find squinting and distortion in the radiation pattern. In that case if end fire is required i suggest a planar quasi yagi antenna or SIW Vivaldi antenna.
As far as the design of vivaldi goes its just a cosine curve. generate in matlab and export it to HFSS and mirror the curve to get the required notch in the ground plane. (Vivaldi is basically a notched version of the ground plane)
To adjust the resonant frequency adjust the feed placement, width and length of the feed, some change in the notch can also result in change in resonant frequency.
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