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Horn Antenna Aperture Sizing Based on Operating Frequency

Pyramidal horn antennas require proper aperture sizing to meet gain and phase error specifications. Aperture width and height relate to horn axial length and operating wavelength. Purely frequency-based scaling ensures minimum cutoff avoidance but may not optimize gain. Designers often use √(3λL) and √(2λL) for width and height or adjust to approximate λ for typical 10 dBi gain.

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By Anusha Answered 1 year ago

For an initial design, the aperture size isn't dictated by frequency alone, but by your desired gain or beamwidth. However, to ensure efficient radiation and avoid excessive phase error across the aperture, the minimum dimension is roughly one wavelength (λ). A common starting point for a gain of ~20 dBi is to size each aperture dimension to 3-5λ. Here's my practical approach: First, determine your feed waveguide dimensions (e.g., WR-90 for 10 GHz, 22.86mm x 10.16mm). The aperture height (B) is often scaled from the waveguide height. Then, for a target half-power beamwidth (HPBW) in degrees in a given plane, use the approximation: Aperture (in λ) ≈ 70° / HPBW(degrees). So, for a 20° E-plane beamwidth at 10 GHz (λ=30mm), start with A ≈ 70/20 = 3.5λ ≈ 105mm. This gives you a rational starting point for further optimization of the horn's length and flare angles.

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