Pyramidal Horn Antenna Calculator
Estimate horn aperture dimensions, beamwidth, and recommended horn length from frequency and target gain.
This is a first-pass engineering estimate for a rectangular pyramidal horn. Final designs should be verified with EM simulation and measurement.
What this horn antenna calculator does
This tool helps you quickly size a pyramidal horn antenna for microwave or millimeter-wave projects. If you know the operating frequency and the gain you want, it estimates the required aperture area, aperture width and height, typical beamwidth, and a practical starting horn length.
It is useful for early-stage design of radar, satcom feeds, test ranges, RF labs, and educational builds where you need a fast answer before detailed optimization.
Inputs explained
1) Operating frequency
Frequency sets the wavelength. As frequency rises, wavelength becomes smaller, so physical antenna size for a given gain also shrinks.
2) Target gain (dBi)
Higher gain requires a larger effective aperture. A jump from 20 dBi to 25 dBi is not small—it means substantially more aperture area.
3) Aperture efficiency
Efficiency captures real-world losses and field taper effects. Typical practical values are often in the 50% to 70% range for first estimates.
4) Aperture aspect ratio (a/b)
This controls how “wide” versus “tall” the aperture is. Changing aspect ratio shifts E-plane and H-plane beamwidth balance.
5) Flare half-angle
The flare angle influences mechanical length. Smaller flare angles generally create longer horns; larger angles make horns shorter but can hurt pattern quality if pushed too far.
Core equations used
- Wavelength: λ = c / f
- Gain (linear): G = 10(GdBi/10)
- Required aperture area: A = (G × λ2) / (4πη)
- Rectangular aperture dimensions from aspect ratio r = a/b:
a = √(A × r), b = √(A / r) - Approximate beamwidth:
HPBWE ≈ 56λ/a, HPBWH ≈ 67λ/b
These relationships are widely used for quick design sizing. Exact performance depends on mode content, throat transition, edge taper, and manufacturing quality.
How to use the results
- Aperture (a, b): starting dimensions for the horn opening.
- Estimated horn length: practical mechanical length based on flare angle and simple throat assumptions.
- HPBW E/H: expected half-power beamwidth in principal planes.
- Far-field distance: minimum test range distance where pattern measurements are more reliable.
Worked design intuition
At 10 GHz with around 20 dBi target gain and 60% efficiency, you should expect a horn aperture on the order of a few centimeters to over 10 cm depending on aspect ratio. The beam narrows as aperture grows. If you need a tighter beam, increase gain target and accept larger physical size.
Practical build tips
- Match the throat to your waveguide standard and frequency band.
- Use smooth interior surfaces; roughness increases loss at high frequency.
- Keep seams and joints electrically tight to reduce leakage.
- Validate return loss (S11), gain, and pattern in measurement.
- For critical systems, verify with full-wave simulation before fabrication.
Limitations
This calculator is intended for quick sizing, not final certification design. Real horn antennas can deviate due to finite wall thickness, dielectric loading, feed mismatch, corrugation, truncation, and manufacturing tolerance.