Visualize radiation patterns of half-wave dipole, monopole, patch, and Yagi-Uda antennas on a polar chart in real time. Automatically calculates directivity, HPBW, and front-to-back ratio.
$$F(\theta) = \frac{\cos\!\left(\frac{\pi}{2}\cos\theta\right)}{\sin\theta}$$
半波長ダイポールの放射パターン。θ=0°（アンテナ軸）で0、θ=90°（赤道面）で最大
$$D = \frac{4\pi U_{\max}}{P_{\text{rad}}} \quad [\text{dBi}]$$
指向性 D：最大放射強度 U_max と全放射電力 P_rad の比。半波長ダイポール ≈ 2.15 dBi
$$P_{\text{EIRP}} = P_{\text{in}} \cdot G$$
等方放射換算電力 EIRP。G：アンテナ利得（線形）、P_in：入力電力 [W]
The radiation pattern is derived from the electromagnetic fields radiated by currents on the antenna. A fundamental model is the field from a Hertzian dipole (a very short current element), which forms the building block for more complex antennas.
$$E_\theta = j \frac{\eta I_0 \ell}{2 \lambda r}\sin\theta \, e^{-jkr}$$Where $E_\theta$ is the far-field electric field strength, $\eta$ is the impedance of free space (~377 Ω), $I_0$ is the current, $\ell$ is the dipole length, $\lambda$ is the wavelength, $r$ is the distance, $\theta$ is the angle from the antenna axis, and $k$ is the wave number. The $\sin\theta$ term defines the classic "doughnut" shape.
A key performance metric is Directivity ($D$), which compares the antenna's maximum radiation intensity to that of an isotropic radiator (which radiates equally in all directions). It's often expressed in decibels as dBi.
$$D = \frac{4\pi}{\Omega_A}\quad \text{or}\quad D_{\text{(dBi)}}= 10 \log_{10}(D)$$Here, $\Omega_A$ is the beam solid angle—the area of the radiation pattern's main lobe. A higher directivity means a more focused beam. The simulator calculates this for each antenna type; for example, a half-wave dipole has $D \approx 2.15$ dBi.
Mobile Communication Base Stations: The panels on cell towers often use patch antennas, which you can select in the simulator. Their relatively broad, hemispherical pattern is ideal for covering users on the ground in a sector below the tower. Engineers use pattern visualizations to minimize dead zones.
Television Reception: The classic rooftop Yagi-Uda antenna is designed for high directivity. Its sharp radiation pattern, visible when you select it in the tool, allows it to be precisely aimed at a distant broadcast tower to maximize signal strength and reject interference from other directions.
Aviation & Maritime: Monopole antennas with a ground plane are ubiquitous on ships and aircraft. The pattern you see with "Ground Plane" enabled—radiating efficiently along the horizon—is crucial for long-range communication over water or between air traffic control and planes.
Wi-Fi Routers: Modern routers often use dipole-like antennas or antenna arrays. The radiation pattern determines coverage within a home. A pattern that is too focused might leave dead spots, while an omnidirectional one (like a dipole's XY-plane view) provides general coverage in all horizontal directions.
There are a few key points you should be especially mindful of when starting to use this tool. The first is that the radiation pattern also represents receiving characteristics. While the visualization shows "transmission strength," antenna characteristics are reciprocal between transmission and reception (the reciprocity theorem). Therefore, a narrow, elongated pattern not only means it "can transmit far" but also that it "can effectively pick up weak radio waves from a distance." The second point is confusion between "dBi" and "dBd". The "Directivity (dBi)" displayed by the tool uses a hypothetical omnidirectional antenna (isotropic antenna) as the 0dB reference. In practice, "dBd," which uses a half-wave dipole as the 0dB reference, is also commonly used. For example, this tool shows the gain of a half-wave dipole as approximately 2.15 dBi, but in dBd, that's about 0 dBd. Pay close attention to this difference when reading catalog values. The third point is the gap between simulation and real devices. This tool shows the characteristics of the "antenna alone" in an ideal environment (free space). In reality, the pattern distorts due to the influence of nearby metal objects (supports, roofs) or the ground. For instance, turning the "ground plane" OFF for a monopole will display a pattern for the lower half that doesn't exist in reality; for an actual vehicle-mounted antenna, the car body acts as the ground, significantly altering the pattern.
A half-wave dipole antenna at 2.4 GHz (λ = 125 mm) with element length 62.5 mm exhibits maximum radiation perpendicular to its axis. Directivity = 1.64 dBi, front-to-back ratio = 3.2 dB, 3dB beamwidth = 78 degrees in azimuth. A Yagi-Uda array with 1 driven element + 4 directors (spacing 0.3λ) at 915 MHz achieves 9.2 dBi directivity with 65-degree main lobe and 18 dB side lobe suppression. Patch antenna on FR-4 substrate (h = 1.6 mm, εr = 4.3) at 5.8 GHz yields 5.1 dBi gain with elliptical radiation pattern tilted 12 degrees from normal.