Antenna Radiation Pattern (Polar Plot) | RFCalcLab
Visualize antenna gain and directivity with interactive polar plots. Analyze HPBW, Front-to-Back ratio, and beam patterns for dipole, Yagi, and parabolic dish antennas.
How to Use the Antenna Pattern Viewer
Select an antenna type from the list (Isotropic, Half-wave Dipole, 3- or 5-element Yagi, or Parabolic Dish) to visualize its typical 2D radiation pattern as a polar plot. The viewer uses representative textbook parameters: an isotropic reference at 0 dBi, a half-wave dipole at about 2.15 dBi, a 3-element Yagi near 7 dBi, a 5-element Yagi near 10 dBi, and a parabolic dish around 20 dBi. The half-wave dipole curve follows the classic cos(π/2·cosθ)/sinθ field shape.
The plot shows normalized gain in dB, with concentric rings at 0, −10, −20, and −30 dB and 0° pointing forward. The HPBW (Half-Power Beamwidth) is the angle where gain drops by 3 dB, defining the main lobe width: roughly 78° for a dipole, 60° for a 3-element Yagi, 45° for a 5-element Yagi, and just 12° for a dish. Narrower beamwidth concentrates energy and corresponds to higher gain.
Front-to-Back (F/B) ratio indicates how much more power is radiated forward versus backward, a key metric for directional antennas like Yagis. The presets here use about 10 dB for a 3-element Yagi, 15 dB for a 5-element Yagi, and 30 dB for a dish, while a dipole is bidirectional (0 dB F/B). A high front-to-back ratio is desirable on point-to-point links because it pushes energy toward the receiver and rejects interference arriving from behind the antenna.
Related Topics
- antenna pattern
- polar plot
- dipole
- Yagi
- parabolic dish
- radiation pattern
- beamwidth
- antenna gain
Frequently Asked Questions
- What does a polar plot show?
- A polar plot shows the relative strength of the signal radiated by an antenna in different directions. It helps engineers visualize the antenna's directivity and gain.
- What is HPBW?
- HPBW stands for Half-Power Beamwidth. It is the angular width of the antenna's main lobe between the points where the power has dropped by 3 dB (half) from the peak gain.
- Why does front-to-back ratio matter?
- A high front-to-back ratio is desirable for point-to-point links because it ensures most power goes toward the receiver and minimizes interference from sources behind the antenna.