The Vivaldi antenna, also known as the Conical Slot Antenna (TSA), is an ideal antenna for broadband applications. It is very popular because it is simple in structure, easy to manufacture, and has a high gain. When designing a Vivaldi antenna, we can use simulation software to calculate its far field mode and impedance.
Origin of the name
The Vivaldi antenna was invented by Peter Gibson. Gibson loves music, and that's probably why he chose to name this antenna with the name of Baroque composer Antonio Vivaldi. Although there are multiple story versions, Gibson is most likely chosen because the shape of the antenna is similar to that of a Vivaldi era, similar to the cross section of a violin, cello or trumpet.
a universal antenna
The Vivaldi antenna is highly malleable. The antenna is built on a flexible, thin substrate and is therefore adaptable to a variety of surfaces; this also means it can be used in a variety of applications in different environments.
One patent involves the use of dual Vivaldi unit feeds in the aircraft, which is due to the streamlined nature of the antenna. Another reason why another Vivadi antenna can be used in an airplane is that it can handle speeds up to 2 Mach. Such antennas are now maturing.
You can also see the Vivaldi antenna in the hospital. Combined with antenna and microwave imaging technology, doctors can better detect breast and brain cancer.
When using the Vivaldi antenna for breast cancer screening, an interferometer called I-MUSIC is used. MUSIC is not the music written by composer Vivaldi. I-MUSIC is an acronym for Interferometric MulTIple Signal Classifica (TION) and has now evolved into a powerful method for tumor detection.
The Vivaldi antenna (in itself and modified) has a wide range of applications. Security personnel can use it to detect hidden weapons, and military personnel can place it as a high-range radar in an array structure.
This general-purpose antenna can perform many functions, but first we want to analyze the design of the antenna to understand how it works.
Analysis of the design of the Vivaldi antenna with simulation
We analyzed the antenna's far-field mode and impedance using the Vivaldi Conical Slot Antenna (TSA) model to analyze the antenna.
Our model simulates a real Vivaldi antenna design that uses a dielectric thin layer substrate to characterize the antenna. On top of the substrate, a layer of perfect electrical conductor (PEC) ground plane pattern is attached to the tapered groove. We obtained the curve of the tapered groove by the exponential function e0.044x. The tapered slot itself looks a bit like a horn, and the wide end gradually bends into a narrower line. But unlike the horn, the thin end is connected to a circular groove and the wide end is open to the air, as shown in the following figure.
Vivaldi antenna geometry
Inverting the substrate will reveal a 50 Ω shorted microstrip feed line that simulates as a PEC surface. This is a key design unit because the lumped port on the line will be used to excite the antenna.
A perfect matching layer (PML) surrounds the entire analog domain. It functions as an anechoic chamber that absorbs all radiant energy.
After building and solving the antenna model using COMSOL MulTIphysics and RF modules, we obtained many forms of results. The SWR plot shows that our model has good broadband impedance matching. In most simulation ranges, this value is even better than 2:1.
Simulation results in SWR drawing form
We also created a model to show the far field mode. We know that the Vivaldi antenna radiation pattern points to the wide end of the tapered slot. From the model point of view, the far-field mode does show a directional radiation pattern.
3D far field mode at 5.5 GHz
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