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Mobile antenna in 3D: tilt and radiation patterns

How does a mobile antenna direct its signal? In this interactive 3D view, you can change its tilt, beamwidth and frequency. Explore how these settings affect the model’s radiation pattern, then open the enclosure to see a schematic view of its construction.

Mobile antenna in 3D

Idealised learning model · sector radiation pattern
Common reference: 1800 MHz and 65°
Controls explained ↓
Using the view & keyboard

Drag with the mouse or choose a view. On a phone, switch on touch rotation when needed. With a keyboard, focus the view and use the arrow keys.

Loading the 3D view …
Three-dimensional antenna with adjustable directivity.
Relative model range −3 dB contour Reference: 1800 MHz · 65° · same electrical tilt
Free-space model · no metre scale · no coverage prediction
On this page

Using the view

Start with “Side view” and “Top view”. From the side, you can see the downward tilt. From above, you can see how widely the sector radiates horizontally. “Rotate 3D” shows the spatial pattern; clicking again turns the camera a little further. You can also drag with the mouse to rotate the view freely.

“Close-up” takes you nearer to the front antenna. Choose “Open enclosure” to remove its cover and reveal eight example crossed dipoles, feed paths and a reflector. The coloured radiation pattern is hidden while the enclosure is open so you can see the interior clearly.

On a phone, you can initially scroll over the view as usual. Switch on “Enable touch rotation” when you want to rotate it, then switch it off to continue scrolling. With a keyboard, reach the view using Tab and rotate it with the arrow keys. “Reset” restores the starting values and the overall 3D view.

The controls explained

Electrical tilt: moving the main beam downwards

Electrical tilt changes the beam direction while the antenna enclosure stays in place. Differences in the phases of the signals fed to the antenna elements change the direction in which their radiated waves reinforce one another most strongly. In this model, you can tilt the main beam downwards from 0° to 15°. This is easiest to follow in the side view.

Mechanical tilt: tilting the entire antenna

Mechanical tilt changes the position of the enclosure on the mast. The antenna and its entire radiation pattern rotate together. To compare the two methods, first set electrical tilt, then mechanical tilt, to the same value. Watch the enclosure to see the difference. In the model’s forward symmetry plane, the two tilts add together: 6° electrical and 4° mechanical give a 10° downward main-beam direction.

Beamwidth: how wide is the sector?

Beamwidth describes the horizontal width of the main lobe. It is measured between the two directions where radiated power has fallen to half its maximum, approximately −3 dB. A width of 65° therefore extends about 32.5° to each side of the main direction. Radiation continues beyond these angles.

At 30°, the model concentrates more power forwards. At 120°, it spreads the power more widely. This control compares different radiation patterns. For an actual passive sector antenna, construction determines its beamwidth; the data sheet describes the available variants and adjustment options.

Frequency: why do the length and shape change?

The frequency selector covers 700 to 2600 MHz. This comparison assumes the same effective vertical antenna length at each frequency. As frequency rises, the vertical main lobe becomes narrower. You set the horizontal width independently with the beamwidth control.

Frequency also changes the length of the lobe. The common reference is 1800 MHz with a horizontal beamwidth of 65°. The free-space calculation gives a longer relative range at lower frequencies and a shorter one at higher frequencies. With “Same transmitter power”, the calculation also includes the model’s changing directivity. The narrower vertical lobe at higher frequencies concentrates the radiation more strongly, offsetting part of the frequency effect.

For reception, the model assumes the same antenna gain in dBi and the same receive threshold at every frequency. Real multiband antennas and phones have band-dependent properties. Assessing those devices requires suitable antenna and device data. The model lobe shows a comparison under the assumptions defined here.

Comparing transmitter power and EIRP

Under “Power comparison”, choose what stays constant as you change beamwidth and frequency:

  • Same transmitter power: total radiated power stays constant in this lossless model. Narrower beamwidth concentrates more power in the main direction and increases the relative main-beam range.
  • Same main-beam EIRP: power in the main direction stays constant, expressed as the equivalent power of an ideal antenna radiating equally in every direction. The model adjusts transmitter power to compensate for the antenna’s directivity. Changing beamwidth then leaves the main-beam range unchanged. Changing frequency still affects range through the frequency factor in the free-space calculation.

Try this: select 1800 MHz, 6° electrical tilt and 0° mechanical tilt. Reduce the beamwidth from 65° to 30°. At the same transmitter power, the model gives about 3.1 dB more directivity and a relative main-beam range of 1.42. Then select the same EIRP: the range factor becomes 1.00. These values follow from the assumptions of this learning model.

Reading the result

The blue surface shows how far the signal would reach in different directions under the model conditions. A point farther from the origin represents a longer calculated relative range in that direction. The dashed contour marks directions with 3 dB less power than the main maximum.

Three values appear below the view:

  • Relative main-beam range: 1.00 represents a 65° sector at 1800 MHz and the currently selected electrical tilt. Every frequency uses this reference. A factor of 1.42 means about 42 per cent more distance under the model conditions.
  • Directivity change: the change in concentration compared with the 65° sector at 1800 MHz and the same electrical tilt. Both horizontal beamwidth and frequency-dependent vertical width contribute. The value is a difference in dB.
  • Beam direction: the main beam’s downward angle in the forward symmetry plane, where electrical and mechanical tilt add together.

Try a frequency comparison: choose “Same main-beam EIRP”. The range factor is about 2.57 at 700 MHz, 1.00 at 1800 MHz and 0.69 at 2600 MHz. At the same transmitter power, the factors differ because antenna directivity also contributes. The drawing keeps the same scale as you adjust the controls. The ground grid, mast and person provide context without a metre scale.

The view clips the lobe at the drawn ground plane. The displayed range factor still describes the calculated main beam when part of the lobe would extend below that plane. Interactions between the radio wave and the ground are not simulated.

Model assumptions and calculations

The view uses a freely parameterised substitute pattern for one sector. Its shape draws on the quadratic attenuation expressions in 3GPP TR 38.901, Table 7.3-1. This sector model uses parameters chosen for explanation. The standard’s element pattern and a fully calculated antenna array describe different levels of modelling.

  • Vertical beamwidth: 9° at 1800 MHz. At other frequencies, it is scaled by 1800 MHz divided by the selected frequency. Horizontal width is set separately.
  • Electrical tilt: the maximum is shifted within the vertical pattern in an idealised way. Mechanical tilt then rotates the entire pattern in space.
  • Power balance: directivity is calculated by numerically integrating the pattern over all directions. Efficiency is set to 100 per cent, so antenna and cable losses are left out.
  • Relative range: free-space propagation in the far field, the same receiving antenna gain in dBi and the same receive threshold are assumed. The common reference is a 65° sector at 1800 MHz with the same electrical tilt. The distance includes the frequency factor 1800 MHz divided by the selected frequency. At constant transmitter power, it also includes the square root of the directivity ratio.
  • Receiving antenna: constant gain in dBi is a model assumption. Its effective receiving area therefore changes with frequency. The model does not reproduce a particular phone’s antenna performance.
  • Interior: the drawn dipoles and feed paths illustrate a construction principle. The substitute radiation pattern is calculated separately. The other mast antennas and microwave dish provide spatial context.
The model equations

Relative attenuation is A = min(12 · (α/H)² + 12 · ((ε + tₑ)/V)², 30) in dB. Here, α is the azimuth offset, ε the elevation angle before mechanical rotation, H the horizontal beamwidth, V the vertical beamwidth and tₑ the electrical tilt. All angles are in degrees.

The vertical beamwidth is V = 9 · 1800 / f, with f in MHz. Attenuation is capped at 30 dB. The radius in each direction is scaled by 10^(−A/20) to represent the relative distance derived from the free-space relationship.

Integrating the linear power pattern over all directions gives directivity D. At constant transmitter power, r/r_ref = (1800/f) · √(D/D_ref). At constant main-beam EIRP, r/r_ref = 1800/f. Frequency f is in MHz. D_ref is the directivity at 1800 MHz, 65° beamwidth and the current electrical tilt. Mechanical rotation leaves directivity unchanged. Receiving antenna gain in dBi and receive threshold stay constant in both cases.

What the model leaves out

The view helps you explore tilt, concentration and power assumptions separately. Assessing real coverage also requires terrain, buildings, vegetation, shadowing, diffraction and reflections. Interaction with the ground is left out; the meadow forms part of the illustration.

Other effects left out include a real array’s sidelobes, polarisation losses, coupling between elements, mismatch and cable losses, and efficiency changes during beam steering. The schematic interior contains neither an RF circuit simulation nor a calculation of Massive MIMO or digital beamforming.

The calculation also leaves out the return link from the phone to the base station, interference from other transmitters, cell load and processing within the mobile network. Data rates, signal bars, compliance limits and coverage at an address require additional information. For a location assessment, use appropriate planning data and measurements on site.

Sources and further reading

For more on these topics, read LTEmobile’s articles on 5G range at different frequencies, 5G frequencies and bands and checking LTE coverage and reception.

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