Parabolic Reflector Antenna Calculator: Complete Guide
A parabolic reflector antenna, commonly called a dish antenna, is one of the most widely deployed high-gain antenna types across satellite communications, radio astronomy, radar systems, and point-to-point microwave links. Its geometry — a paraboloid of revolution — focuses incoming plane waves to a single point (the focal point) where the feed element is positioned, enabling remarkably high directivity at microwave and millimetre-wave frequencies. Understanding how to calculate and optimise dish antenna parameters is essential for satellite ground station engineers, telecom system planners, and RF researchers.
Parabolic Dish Gain Formula
The fundamental gain equation for a circular parabolic reflector is: G = η × (π × D / λ)², where η is the aperture efficiency (typically 0.55–0.70 for practical designs), D is the dish diameter in metres, and λ is the free-space wavelength in metres computed as λ = c / f (c = 3×10⁸ m/s). In dBi: G(dBi) = 10 × log₁₀(G). A 1.2 m dish operating at 12 GHz with η = 0.6 delivers approximately 40.7 dBi of gain.
Beamwidth and Focal Length
The 3 dB half-power beamwidth (HPBW) is approximated by HPBW ≈ 70λ/D degrees. The focal length is derived from the dish geometry: f = D² / (16 × d), where d is the dish depth at its centre. The f/D ratio is a critical design parameter — values between 0.3 and 0.5 balance feed illumination efficiency against spillover loss.
Practical Examples
- Ku-band VSAT (0.9 m, 14.25 GHz, η = 0.60): Gain ≈ 38.5 dBi, HPBW ≈ 1.6°.
- C-band satellite TV (1.8 m, 4 GHz, η = 0.65): Gain ≈ 32.0 dBi, HPBW ≈ 5.8°.
- Ka-band radar (0.3 m, 35 GHz, η = 0.70): Gain ≈ 38.3 dBi, HPBW ≈ 1.7°.
Applications
Parabolic reflector antennas power global satellite broadband networks (VSAT, HTS systems), direct broadcast satellite (DBS) television, deep-space tracking stations, weather radar, air traffic control, and 5G millimetre-wave backhaul. In radio astronomy, large dishes up to 100 m diameter achieve extraordinary sensitivity and angular resolution for observing distant galaxies. This calculator helps engineers rapidly prototype antenna designs, conduct frequency-scaling trade studies, and build accurate link budgets.