What types of horn antennas exist?

Pyramidal horn: rectangular waveguide flared in both E and H planes. Most common for measurements. Gain: 10-25 dBi. Predictable gain from dimensions alone (within 0.5 dB). Conical horn: circular waveguide flared into a cone. Used for circular polarization and reflector feeds. Corrugated horn: inner walls have circumferential grooves (corrugations). Creates hybrid HE11 mode with symmetric E and H patterns, very low cross-polarization (<-30 dB), and low sidelobes. Standard for reflector feeds in satellite and radio astronomy. Dual-ridged horn: wide bandwidth (10:1 or more), lower gain. Used for EMC testing and wideband measurements. Diagonal horn: square aperture rotated 45 degrees. Moderate gain, good pattern symmetry.

What is a standard gain horn?

A standard gain horn (SGH) is a precision-machined pyramidal horn with gain that can be calculated from its physical dimensions to within +/-0.5 dB (or better with corrections). The gain is: G = 4*pi/(lambda^2) * epsilon_E * epsilon_H * a * b, where a and b are the aperture dimensions and epsilon_E, epsilon_H are the aperture efficiencies that depend on the horn length and flare angles. SGHs are used as reference antennas in antenna measurements: the gain of an unknown antenna is determined by substituting it for the SGH and comparing received power. This is the gain transfer method. Companies like Narda, ETS-Lindgren, and A-INFO manufacture calibrated standard gain horns covering 1-325 GHz with gain uncertainties of +/-0.25 to +/-0.5 dB.

How are horn antennas used as reflector feeds?

The horn illuminates the parabolic reflector surface with an approximately Gaussian field pattern. The reflector collimates this into a pencil beam. Feed horn requirements: (1) Edge taper: the illumination should be approximately -10 to -12 dB at the reflector edge. Too little taper wastes feed energy past the dish (spillover). Too much reduces the effective aperture. (2) Phase center: the horn's phase center must be at the focal point of the parabola. The phase center location depends on the horn length and flare angle. (3) Cross-polarization: should be <-25 dB to avoid coupling between orthogonal polarization channels (important for dual-pol satellite systems). Corrugated horns are preferred for feeds because their symmetric patterns and low cross-pol yield the highest aperture efficiency (70-80%).

Antenna Types

Horn Antenna

Q: What is a standard gain horn?

A standard gain horn (SGH) is a precision-machined pyramidal horn with gain that can be calculated from its physical dimensions to within +/-0.5 dB (or better with corrections). The gain is: G = 4*pi/(lambda^2) * epsilon_E * epsilon_H * a * b, where a and b are the aperture dimensions and epsilon_E, epsilon_H are the aperture efficiencies that depend on the horn length and flare angles. SGHs are used as reference antennas in antenna measurements: the gain of an unknown antenna is determined by substituting it for the SGH and comparing received power. This is the gain transfer method. Companies like Narda, ETS-Lindgren, and A-INFO manufacture calibrated standard gain horns covering 1-325 GHz with gain uncertainties of +/-0.25 to +/-0.5 dB.

Q: How are horn antennas used as reflector feeds?

The horn illuminates the parabolic reflector surface with an approximately Gaussian field pattern. The reflector collimates this into a pencil beam. Feed horn requirements: (1) Edge taper: the illumination should be approximately -10 to -12 dB at the reflector edge. Too little taper wastes feed energy past the dish (spillover). Too much reduces the effective aperture. (2) Phase center: the horn's phase center must be at the focal point of the parabola. The phase center location depends on the horn length and flare angle. (3) Cross-polarization: should be <-25 dB to avoid coupling between orthogonal polarization channels (important for dual-pol satellite systems). Corrugated horns are preferred for feeds because their symmetric patterns and low cross-pol yield the highest aperture efficiency (70-80%).

/horn an-ten-ah/

A horn antenna is a flared waveguide aperture providing 10-25 dBi gain with broadband performance. G = 4πε_apA/λ². Standard gain horns (SGHs): ±0.5 dB accuracy from dimensions alone. Types: pyramidal (measurements), conical (circular pol), corrugated (low cross-pol feeds, <-30 dB), dual-ridged (10:1 BW, EMC). Primary feed for parabolic reflectors.

Gain: 10-25 dBi

SGH accuracy: ±0.5 dB

Feed X-pol: <-30 dB

Understanding Horn Antennas

The horn antenna is one of the most important antenna types in microwave engineering. Its simple construction (flared metal waveguide) produces predictable, calculable gain without complex feeding networks. This makes it the gold standard for antenna measurements: you can determine a horn's gain from its physical dimensions alone, to within 0.5 dB. Corrugated horns, with their symmetric radiation patterns and ultra-low cross-polarization, are the standard feeds for satellite communication and radio telescope reflectors.

Horn Antenna Gain

Pyramidal horn gain:
G = (4π/λ²)·η_ap·A·B
A, B = aperture dimensions

Optimum horn (equal E/H):
A = √(3λR), B = √(2λR)
R = horn length

3 dB beamwidth:
θ_E ≈ 54λ/B, θ_H ≈ 67λ/A

Horn Antenna Type Comparison

Type	Gain	Bandwidth	Cross-Pol	Pattern	Application
Pyramidal	10-25 dBi	~40% (waveguide)	-20 dB	Asymmetric	SGH, measurement
Conical	10-20 dBi	~40%	-15 to -25 dB	Moderate sym	Circular pol feed
Corrugated	10-22 dBi	~30-40%	<-30 dB	Excellent sym	Reflector feed
Dual-ridged	5-15 dBi	10:1+	-15 dB	Moderate	EMC, wideband
Quad-ridged	5-15 dBi	10:1+	-20 dB	Dual-pol	SIGINT, EW

Key Equations

Friis transmission:
P_r = P_tG_tG_r(λ/4πd)²

Antenna gain:
G = η_ap × 4πA_eff/λ²

Beamwidth (3 dB):
θ ≈ 70λ/D degrees

Comparison

Band	Gain	Aperture	Beamwidth	Model
C-band	15 dBi	8×6 cm	30×35°	Standard gain
X-band	20 dBi	6×5 cm	18×22°	Standard gain
Ku-band	22 dBi	4×3 cm	12×15°	Corrugated
Ka-band	25 dBi	3×2 cm	8×10°	Corrugated
W-band	25 dBi	15×12 mm	6×8°	Diagonal

Common Questions

Frequently Asked Questions

Types?

Pyramidal: rectangular, most common for measurements. Conical: circular waveguide. Corrugated: best cross-pol (<-30 dB), standard for reflector feeds. Dual-ridged: ultra-wideband (10:1), EMC testing. Diagonal: good symmetry.

Standard gain horn?

Precision-machined pyramidal horn. Gain calculated from dimensions to +/-0.5 dB. Used as reference in gain transfer method. Available 1-325 GHz from Narda, ETS-Lindgren, A-INFO. Calibrated uncertainty 0.25-0.5 dB.

Reflector feed?

Illuminates parabolic dish. Edge taper: -10 to -12 dB at reflector edge. Phase center at focal point. Corrugated: 70-80% aperture efficiency. Cross-pol <-25 dB needed for dual-pol satellite systems.

Related Terms

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