The bowtie antenna is a usual dipole, however, due to the large “thickness” at the ends, it has a much wider bandwidth compared to a linear dipole. For the same reason, the antenna length L is much shorter than the length of a linear dipole.
Don't forget about antenna polarization. In the figure, the antenna has a horizontal polarization. Constructively, the antenna can be cut out of a sheet of tin with dimensions of 2:1 (W:H). Antenna triangles are gotten by dividing this sheet diagonally. Then the sharp end of each triangle is cut off by g/2.
Schematic representation of the antenna:
Javascript source code:
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Limitations and features of antenna calculations
The antenna has an electrical length close to half the wavelength (physical length L about 0.3λ), and has an input impedance of about 50 ohms. Any 1:1 balun can be used for balancing with 50 ohm coaxial cable. The antenna also has resonance at about twice the frequency close to the wavelength (physical length is about 0.7λ), but its input impedance in this case is more than 300 ohms. Such high-resistance bowties are most often computed in other similar calculators. They are usually used as part of antenna arrays in UHF TV antennas using 4: 1 broadband ferrite baluns to match the feeder. On the microwave, such a solution, to put it mildly, is quite problematic, so a half-wave bowtie is chosen here. Below are the results of modeling the antenna in ANSYS HFSS by dimensions from this calculator for the LTE1800 band (click on the desired image to enlarge).
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| Input impedance | VSWR | Input impedance with wave resonance capture |
A calculation similar to this calculator is available in the android application Dipole Antenna Calculator, available on Google play. You can download it to your mobile device by tapping or by scanning the QR code. Don't forget to rate the app...
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