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Spacecraft and antenna sizing

Antenna Gain & Aperture Calculator

Relate dish size, aperture efficiency, gain and pointing tolerance.

Given / choose the units

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Enter the design inputs, then calculate to inspect the results.

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Approximation / normalized main lobeD 2 m · 10.00 GHz · η 70%
Polar main-beam approximation0.000°, 0.00 dBPolar view / normalized radiusRelative main-beam power versus off-axis angleHPBW 1.124° · half-power ±0.562°−6.00°0°+6.00°Off-axis angle / relative power dB
Gaussian aperture approximation, normalized to peak power. Blue shows calculated relative power, amber marks boresight and the selected probe, and teal marks the −3.01 dB half-power boundaries. Diameter and frequency update both views. This is not a measured radiation pattern; sidelobes are not modeled.

Understand the system

Physical versus effective aperture

A circular dish has projected area πD²/4. Effective aperture is efficiency times physical area; it represents the power captured from incident flux. At 10 GHz, 2 m and 70% efficiency, area is 3.1416 m² and effective area 2.1991 m².

A=πD2/4,Ae=ηA,G=4πAe/λ2A=\pi D^2/4,\quad A_e=\eta A,\quad G=4\pi A_e/\lambda^2

D, λ: m; A, A_e: m²; η: fractional efficiency; G: linear power gain.

A physical aperture is an area, not a dimensionless gain.

Source: finalExam.pdf · PDF page 4

Common mistakes

  • Use power gain 10 log, not voltage gain 20 log.
  • Efficiency is 0.70, not 70.
  • Area in dB needs the explicit reference 1 m².
Formula reference and symbol definitions

Physical aperture

A=πD2/4A=\pi D^2/4

A: m²; D: m

Circular projected aperture.

Example: For D = 2 m, A = π × 2²/4 = π ≈ 3.142 m².

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Effective aperture

Ae=ηAA_e=\eta A

A_e,A: m²; η: fraction

Aperture efficiency defined consistently.

Example: For A = 3.142 m² and η = 0.70, Aₑ ≈ 2.199 m².

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Aperture gain

G=4πAe/λ2G=4\pi A_e/\lambda^2

G: linear; λ: m

Matched polarization and reciprocal antenna.

Example: For Aₑ = 1 m² and λ = 0.1 m, G = 4π/0.01 ≈ 1256.64 (linear).

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Parabolic gain

G=η(πD/λ)2G=\eta(\pi D/\lambda)^2

D,λ: m; η: fraction

Far-field dish approximation.

Example: For D = 2 m, λ = 0.03 m and η = 0.70, G = 0.70(π × 2/0.03)² ≈ 30705.4.

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Gain in dBi

GdBi=10log⁡10GG_{dBi}=10\log_{10}G

G: linear power ratio

Isotropic reference.

Example: A linear power gain of 100 gives G = 10 log₁₀(100) = 20 dBi.

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Course beamwidth

θ3dB≈75λ/D\theta_{3dB}\approx75\lambda/D

θ: degrees; lengths: same units

Approximate course illumination convention.

Example: For D = 2 m and λ = 0.03 m, course HPBW ≈ 75 × 0.03/2 = 1.125°.

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Continue the signal path

RF Band & Carrier Planner →GEO Look Angle Calculator →RF Path, PFD and Received Power Calculator · use this result →Noise, Noise Figure and G/T Calculator →

Design guide

Use the result with engineering context

Technical content reviewed

When this tool is useful

  • Calculating wavelength with engineering models
  • Calculating physical and effective aperture with engineering models
  • Calculating gain and dbi with engineering models

What the result includes

  • Relate dish size, aperture efficiency, gain and pointing tolerance.
  • Explanations, assumptions and links to related satellite calculators

What the model does not guarantee

  • Analytical engineering models do not replace measurements or a mission-specific design review.
  • Spectrum permissions, launch operations and real satellite tracking are outside these calculators.

Worked approach

Wavelength

For the final preset, λ = 0.03 m and gain ≈ 44.87 dBi. dBi compares power gain to an isotropic reference. Doubling dish diameter quadruples area and adds approximately 6.02 dB gain at fixed frequency and efficiency.

Common decisions

Questions engineers ask

Which topics does Antenna Gain & Aperture Calculator cover?

Wavelength; Physical and effective aperture; Gain and dBi; Beamwidth; Sidelobes.

How should I check my work in Antenna Gain & Aperture Calculator?

Read the stated assumptions and source references, check units and independently repeat a worked example before relying on the result.

Does Antenna Gain & Aperture Calculator operate real satellite equipment?

No. This is a browser-based educational resource. It does not transmit RF signals, command spacecraft or certify a working link.

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