Dipole · Yagi · Patch · Phased Array · Polar plot · dBi
Theoretical reference; 100% efficiency
An antenna's radiation pattern describes how it distributes transmitted power across all directions. The pattern is plotted in polar coordinates where radius = relative gain (in dB or linear). An isotropic antenna (theoretical) radiates equally in all directions. A half-wave dipole concentrates radiation in a torus perpendicular to its axis. A Yagi-Uda array adds parasitic directors and reflectors that create a highly directional beam. Phased arrays steer the beam electronically by applying progressive phase shifts to each element, exploiting constructive and destructive interference of the array factor.
Click the antenna type buttons to switch patterns. For Phased Array, drag the Steering Angle slider to electronically steer the main beam without moving any hardware. Toggle between linear and dB scale — the dB view shows side lobe levels clearly. The HPBW (Half-Power Beam Width) annotation shows the −3 dB angular width of the main beam. Note how increasing the number of array elements narrows the beam and increases gain.
Modern 5G base stations use massive MIMO phased arrays with 64–256 antenna elements, steering beams to individual users thousands of times per second. The world's largest phased array radar (HAARP in Alaska) uses 180 crossed-dipole antennas to study the ionosphere. Satellite dish antennas achieve gains of 30–50 dBi by using a parabolic reflector to focus energy into an extremely narrow beam — sometimes less than 0.5° wide.
This simulation plots an antenna's radiation pattern in polar coordinates, where the radius represents relative gain. It computes the linear pattern function for each antenna type across 360 angular steps, normalises to the peak, and renders it on either a logarithmic decibel scale (down to −40 dB) or a linear scale. The half-wave dipole uses the classic cos²(π/2·cosθ)/sin²θ field, while the phased array sums the complex array factor over its elements.
You can switch between isotropic, dipole, monopole, Yagi, patch and phased-array types. For the phased array, sliders set the steering angle (−60° to +60°), element spacing (0.25λ to 1.0λ) and element count (2 to 16). Display toggles control the grid, decibel labels, the half-power beamwidth annotation and the dB/linear scale. Such patterns are central to designing radar, 5G base stations, satellite links and broadcast coverage.
What is an antenna radiation pattern?
It is a graph of how an antenna distributes radiated power across direction. Here it is drawn as a polar plot where the distance from the centre encodes relative gain. A wide, round shape means the antenna radiates broadly, while a narrow lobe means energy is concentrated into a beam.
What do the six antenna-type buttons do?
They switch the underlying pattern function: isotropic (a perfect sphere), half-wave dipole, monopole over a ground plane, a five-element Yagi, a microstrip patch and a steerable phased array. Each uses a different equation, so the polar shape, gain and beamwidth change immediately when you select one.
What does the steering-angle slider on the phased array do?
It electronically tilts the main beam without moving any hardware. The simulation applies a progressive phase shift β = −2π·d·sin(steer) across the elements, so the array factor peaks in the chosen direction. This is exactly how modern phased-array radars and 5G antennas redirect their beams.
HPBW stands for Half-Power Beam Width — the angular width of the main lobe measured between the two points where power falls to half (−3 dB) of the peak. The yellow dashed arc marks it. A narrower HPBW indicates a more directional antenna with higher gain.
The linear scale draws radius proportional to the square root of power, which emphasises the main lobe. The decibel scale is logarithmic (10·log₁₀ of gain, shown down to −40 dB), which compresses the dynamic range so weak side lobes and nulls become visible. Antenna engineers almost always work in dB.
The array factor is the magnitude of the summed phasors exp(j·n·(2π·d·cos(θ−90°)+β)) over all N elements, normalised by N². By choosing the progressive phase β the constructive-interference peak is moved to the desired angle, and multiplying by an element pattern gives the full result.
The frequency slider only updates the displayed wavelength (λ = 30/f cm) for context. The pattern functions are expressed in terms of electrical units such as wavelengths of spacing, so they are already frequency-independent in this normalised view. Real antennas do change with frequency relative to their fixed physical size.
They use standard idealised closed-form models — the analytic dipole field, an end-fire approximation for the Yagi, a cos³ broadside patch and a rigorous array factor for the phased array. They assume 100% efficiency and ignore mutual coupling, feed losses and ground effects, so they are excellent for teaching but not a substitute for full electromagnetic simulation.
A longer array spans a larger aperture, so its array factor has sharper constructive peaks and deeper nulls. As the element count rises the main lobe narrows and gain increases roughly in proportion to N, while more side lobes appear. The simulation shows this directly as you drag the elements slider.
Dipoles and monopoles serve FM radio and mobile handsets, Yagis are common for TV reception and amateur radio, patches sit in GPS receivers and Wi-Fi devices, and phased arrays power radar, satellite communications and 5G massive-MIMO base stations that steer beams to individual users.