prof. girish kumar - nptel · coaxial feed pyramidal horn antenna designed at 900 mhz parameter...
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Horn Antennas
Prof. Girish Kumar Electrical Engineering Department, IIT Bombay
(022) 2576 7436
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Horn Antennas
H-Plane Sectoral Horn E-Plane Sectoral Horn
Pyramidal Horn Conical Horn
TE10 mode in Rectangular Waveguide
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TE10 mode in Rectangular Waveguide
Rectangular Waveguide
b
a
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 1010 / 4.572 = 6.56 GHz
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E-Plane Sectoral Horn Antenna
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E-Plane Sectoral Horn: Side View
≈
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E-Plane Sectoral Horn: Directivity Curve
ρ1 6 10 20 100
b1 3.46 4.47 6.32 14.14
Max. Directivity:
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E-Plane Sectoral Horn: Max. Phase Error
Maximum Directivity occurs when
which gives ‘s’ approximately equal to:
δmax = 90°
δmax = 2πs, where ≈
Maximum Phase error occurs when y’ = b1 / 2
Phase Error too high:
Not Recommended
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E-Plane Sectoral: Universal Pattern
E-Field for s = 1/4 (δmax = 90°)
E-Field for s = 1/8 (δmax = 45°) - Recommended
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H-Plane Sectoral Horn Antenna
δmax = 2πt, where Maximum Phase
error at x’ = a1 / 2
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H-Plane Sectoral Horn: Directivity Curve
Max. Directivity: ρ2 6 10 20 100
a1 4.24 5.48 7.75 17.32 a1 3λρ2
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H-Plane Sectoral Horn: Max. Phase Error
Maximum Directivity occurs when
which gives ‘t’ approximately equal to:
δmax = 135°
δmax = 2πt, where
Maximum Phase error occurs when x’ = a1 / 2
Phase Error too high:
Not Recommended
a1 3λρ2
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H-Plane Sectoral: Universal Pattern
E-Field for t = 1/4 (δmax = 90°)
E-Field for t = 1/8 (δmax = 45°)
Recommended
max. phase
error between
45° and 90°
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Pyramidal Horn Antenna
Side View Top View
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Pyramidal Horn Antenna
Condition for Physical Realization:
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Pyramidal Horn: Design Procedure
Directivity of
Pyramidal Horn
Antenna can be
obtained using
Directivity
curves for E-and
H-Planes
Sectoral Horn
antenna
Alternatively
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Pyramidal Horn Design Steps
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Pyramidal Horn Design: Example
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Pyramidal Horn Design: Example (Contd.)
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Pyramidal Horn Design: Example (Contd.)
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Optimum Dimensions vs. Directivity
Gain (dBi)
aEλ
aHλ
Lλ
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Radiation Pattern of Pyramidal Horn Antenna
E-Plane Pattern H-Plane Pattern
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Coaxial Feed Pyramidal Horn Antenna
E-Plane View
H-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.
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Coaxial Feed Pyramidal Horn Antenna Designed at 900 MHz
Parameter Value
(mm)
Description
A 450 Aperture Width
B 320 Aperture Height
a 240 Waveguide Width
b 120 Waveguide Height
WG_L 110 Waveguide Length
RE = RH 250 Horn Length
l 75 Probe Length
r 3.5 Probe Radius
d_sc 67.5 Distance of feed from short
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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.
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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.
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Effect of Probe Feed Location
As the probe feed location is moved towards shorting
wall (i.e., decreased from 75 to 60 mm), the input
impedance becomes inductive so the curve shifts upward.
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Effect of Horn Length on Efficiency
For Horn Length RE = RH > 150 mm, efficiency > 72%
and for RE = RH > 250 mm, efficiency ≈ 80%
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Effect of Horn Aperture on Directivity
As aperture area increases, directivity increases. But for
larger aperture as frequency increases, phase error
increases, which decreases the gain of the horn antenna.
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Simulated and Measured S11 of Coaxial Feed Pyramidal Horn Antenna
Bandwidth for S11 < -10dB :
CST Simulation : 47%
IE3D Simulation : 49.5%
Measured Results : 52%
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Simulated Radiation Pattern of Coaxial Feed Pyramidal Horn Antenna
Simulated E-Plane
Radiation Pattern
Simulated H-Plane
Radiation Pattern
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Conical Horn Antenna
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Conical Horn: Directivity Curve
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Conical Horn Antenna: Directivity
δmax = 135°
Phase Error too high:
Not Recommended
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Conical Horn Optimum Dimensions vs. Directivity
Gain (dBi)
Dλ
Lλ
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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.
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MSA Integrated with Conical Horn
Suspended CMSA integrated inside a Conical Horn
Antenna. Simulation using IE3D software.
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Radiation Pattern of Integrated Conical Horn
Gain of Suspended CMSA = 9 dB
Gain of Integrated Conical Horn Antenna = 12.5 dB
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Measured Results of Integrated Conical Horn
Measured BW for |S11| < -10 dB is from 2070 to 2210 MHz