Horn Antennas
Prof. Girish Kumar Electrical Engineering Department, IIT Bombay
[email protected] (022) 2576 7436
Horn Antennas
E-Plane Sectoral Horn H-Plane Sectoral Horn TE10 mode in Rectangular Waveguide
Pyramidal Horn
Conical Horn
Rectangular Waveguide a b TE10 mode in Rectangular Waveguide For Fundamental TE10 mode: E-Field varies sinusoidally along ‘a’ and is uniform along ‘b’ X-Band Waveguide WR90 (8.4 to 12.4 GHz): a = 0.9” and b = 0.4” Cut-off Wavelength = 2a = 2 x 0.9 x 2.54 = 4.572 cm Cut-off Frequency = 3 x 10 10 / 4.572 = 6.56 GHz
E-Plane Sectoral Horn Antenna
E-Plane Sectoral Horn: Side View
≈
E-Plane Sectoral Horn: Directivity Curve
Max. Directivity:
ρ1
6
b
3.46
10
20
100
4.47 6.32 14.14
E-Plane Sectoral Horn: Max. Phase Error Maximum Directivity occurs when
Maximum Phase error occurs when y’ = b 1 / 2 ≈
δmax = 2πs, where
which gives ‘s’ approximately equal to:
δmax = 90° 90° Phase Error too high: Not Recommended
E-Plane Sectoral: Universal Pattern
E-Field for s = 1/4 ( δmax = 90° 90°) E-Field for s = 1/8 ( δmax = 45° 45°) - Recommended
H-Plane Sectoral Horn Antenna
Maximum Phase error at x’ = a 1 / 2
δmax = 2πt, where
H-Plane Sectoral Horn: Directivity Curve
Max. Directivity:
a1
3λρ2
ρ2 a1
6
10
20
100
4.24 5.48 7.75 17.32
H-Plane Sectoral Horn: Max. Phase Error Maximum Directivity occurs when
a1
3λρ2
Maximum Phase error occurs when x’ = a 1 / 2
δmax = 2πt, where which gives ‘t’ approximately equal to:
δmax = 135° 135° Phase Error too high: Not Recommended
H-Plane Sectoral: Universal Pattern
E-Field for t = 1/4 ( δmax = 90° 90°) E-Field for t = 1/8 ( δmax = 45° 45°)
Recommended max. phase error between 45°° and 90° 45 90°
Pyramidal Horn Antenna
Side View
Top View
Pyramidal Horn Antenna
Condition for Physical Realization:
Pyramidal Horn: Design Procedure Alternatively Directivity of Directivity Pyramidal Horn Antenna can be obtained using Directivity curves for E-and H-Planes Sectoral Horn antenna
Pyramidal Horn Design Steps
Pyramidal Horn Design: Example
Pyramidal Horn Design: Example (Contd.)
Pyramidal Horn Design: Example (Contd.)
Optimum Dimensions vs. Directivity
Lλ aHλ aEλ
Radiation Pattern of Pyramidal Horn Antenna
E-Plane Pattern
H-Plane Pattern
Coaxial Feed Pyramidal P yramidal Horn Antenna
H-Plane View E-Plane View Reference: Hemant Kumar and Girish Kumar, “Design and Parametric Analysis of Pyramidal Horn Antenna with High Efficiency”, Proceedings of International Symposium on Microwave and Optical Technology (ISMOT) 2015, pp. 134-137.
Coaxial Feed Pyramidal Horn Antenna Antenna Designed at 900 MHz Parameter
Value
Description
(mm) A B a b WG_L R E = R H l r d_sc
450 320 240 120 110 250 75 3.5 67.5
Aperture Width Aperture Height Waveguide avegui de Width Waveguide avegui de Height Waveguide avegui de Length Horn Length Probe Length Probe Radius Distance of feed from short
Effect of Probe Feed Length
As the probe length increases from 70 to 80 mm, the resonance frequency decreases from 895 to 790 MHz and the input impedance curve rotates clockwise. clockwise.
Effect of Probe Feed Radius
As the probe radius increases from 2 to 5mm, the resonance frequency decreases slightly due to increase in the fringing fields and bandwidth increases.
Effect of Probe Feed Location
As the probe feed location is moved towards shorting wall (i.e., decreased from from 75 to 60 mm), the input impedance becomes inductive so the curve shifts upward.
Effect of Horn Length on Efficiency
For Horn Length R E = R H > 150 mm, efficiency > 72% and for R E = R H > 250 mm, efficiency ≈ 80%
Effect of Horn Aperture on Directivity
As aperture area increases, directivity increases. But for larger aperture as frequency increases, phase error increases, which which decreases the gain of the horn antenna.
Simulated and Measured S11 of Coaxial Feed Pyramidal Horn Antenna
Bandwidth for S11 < -10dB : CST Simulation : 47% IE3D Simulation : 49.5% 49 .5% Measured Results : 52%
Simulated Radiation Pattern of Coaxial Feed Pyramidal Horn Antenna Simulated E-Plane Radiation Pattern
Simulated H-Plane Radiation Pattern
Conical Horn Antenna Antenna
Conical Horn: Directivity Curve
Conical Horn Antenna: Directivity Directi vity
δmax = 135° 135°
Phase Error too high: Not Recommended
Conical Horn Optimum Dimensions vs. Directivity
Lλ
Dλ
Gain (dBi)
Measured Pattern of Conical Horn H-Plane Pattern
E-Plane Pattern
20 Log 0.37 = -8.6 dB. Higher SLL due to large phase error.
MSA Integrated with Conical Horn
Suspended CMSA integrated inside a Conical Horn Antenna. Simulation using IE3D software.
Radiation Pattern of Integrated Conical Horn
Gain of Suspended CMSA = 9 dB Gain of Integrated Conical Horn Antenna = 12.5 dB
Measured Results of Integrated Conical Horn
Measured BW for |S11| |S11| < -10 dB is from 2070 to 2210 MHz MHz
