Evaluation of Suitable Feed Systems€¦ · Ring Focus Antenna 13.2m Antennas with Gaussian Beam...
Transcript of Evaluation of Suitable Feed Systems€¦ · Ring Focus Antenna 13.2m Antennas with Gaussian Beam...
Evaluation of Suitable Feed Systemes
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
• Review of the Ring Focus Antenna
• Quadridge Horn
• Eleven Feed
• Coaxial Horn and Multiband Corrugated Horn
• Conclusion
Gain of Reflector Antennas
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
εηηηηηηηBXPSI
=
ηλ
π2
=
DGη
λ
π2
4 AG =
G = antenna gain
A = aperture area
D = antenna diameter
λ = wavelength
ηI= illumination efficiency
ηS
= spillover efficiency
ηX
= crosspolarization efficiency
ηB
= blockage efficiency
ηε = surface error efficiency
Optical Design Ring Focus Antenna
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
Dm
fp
ds
Para
bo
la A
xis
2c
SubreflectorEllipsoid-Axis
Ring Focus
Main Reflector
System Focus
Ring Focus Antenna
13.2m Antennas with Gaussian Beam Feeds (-12dB at Subreflector Rim)
Aperture Effenciency
60
65
70
75
80
85
0 2 4 6 8 10 12 14 16 18
Frequency [GHz]
Ap
ert
ure
-Eff
icie
ncy [%
]
Gregory-Antenna
Dualoffset-Antenna
Ringfocus-Antenna
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
• no field in the blocked center region
• no reflection back to the feed system
• feed can be located close at the subreflector
• high antenna efficiency
• cost-effective mechanical structure
13.2m R ing Focus Antenna
Aperture Field Distribution, f = 5 GH z
-25
-22.5
-20
-17.5
-15
-12.5
-10
-7.5
-5
-2.5
0
-6.5 -6 -5.5 -5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2 .5 3 3.5 4 4 .5 5 5.5 6 6.5
rho [m ]
Rela
tive
Am
pli
tud
e [
dB
]
Quadridge Horn
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
• quadridge waveguide horn
• wide frequency range (2 to 18 GHz)
• dual linear polarization
• VSWR < 3.5:1 (return loss < -5.5 dB)
Quadridge Horn, 3D Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
• elliptical radiation patterns
• frequency dependent radiation characteristic
• moving phase center
2 GHz 8 GHz
16 GHz
Quadridge Horn, Polar Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
• compromise for the subreflector illumination angle at center frequency
• high subreflector spillover at lowest frequency (high antenna noise temperature)
• low illumination efficiency at highest frequency
Quadridge Horn, f = 2.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
10
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
10
Quadridge Horn, f = 8.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
Quadridge Horn, f = 16.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
10
13.2m TTW Atenna Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
13.2m Ring Focus Antenna with Quadridge Horn
f = 16.0 GHz, without VSWR Efficiency and Strut Blockage
0
10
20
30
40
50
60
70
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Angle [deg]
Gain
[d
Bi] 90°_Co
0°_Co
45°_Co
45°_Cr
13.2m Ring Focus Antenna with Quadridge Horn
f = 8.0 GHz, without VSWR Efficiency and Strut Blockage
0
10
20
30
40
50
60
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
Angle [deg]
Gain
[d
Bi] 90°_Co
0°_Co
45°_Co
45°_Cr
13.2m Ring Focus Antenna with Quadridge Horn
f = 2.0 GHz, without VSWR Efficiency and Strut Blockage
-10
-5
0
5
10
15
20
25
30
35
40
45
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Angle [deg]
Gain
[d
Bi] 90°_Co
0°_Co
45°_Co
45°_Cr
13.2m TTW Antenna Efficiency with Quadridge Feed
(without VSWR Efficiency and Strut Blockage)
0
10
20
30
40
50
60
70
0 2 4 6 8 10 12 14 16 18
Frequency [GHz]
Eff
icie
ncy
[%
]
Eleven Feed
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
Dipol Array
Dielectric
Support
Housing
Eleven Feed, 3D Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
2 GHz 8 GHz
16 GHz• rotationally symmetric radiaiton pattern
• frequency-independent feed gain
• fixed phase center
Eleven Feed, Polar Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
Eleven-Feed, f = 8.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
10
Eleven-Feed, f = 16.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
Eleven-Feed, f = 2.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
10
• frequency-independent reflector illumination
• constant efficiency in a reflector antenna
Interaction between Subreflector and Feed Cone
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
insignificant interaction
between subreflector
and feed cone and feed
housing
13.2m TTW Atenna Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
13.2m Ring Focus Antenna with Eleven Feed
f = 16.0 GHz, without VSWR-Efficiency and Strut-Blockage
0
10
20
30
40
50
60
70
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Angle [deg]
Gain
[d
Bi]
90°_Co
0°_Co
45°_Co
45°_Cr
13.2m Ring Focus Antenna with Eleven Feed
f = 8.0 GHz, without VSWR Efficiency and Strut-Blockage
0
10
20
30
40
50
60
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
Angle [deg]
Gain
[d
Bi] 90°_Co
0°_Co
45°_Co
45°_Cr
13.2m Ring Focus Antenna with Eleven Feed
f = 8.0 GHz, without VSWR Efficiency and Strut-Blockage
0
10
20
30
40
50
60
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
Angle [deg]
Gain
[d
Bi] 90°_Co
0°_Co
45°_Co
45°_Cr
13.2m TTW Antenna Efficiency with Eleven Feed
(without VSWR and Strut Blockage Efficiency)
0
10
20
30
40
50
60
70
80
0 2 4 6 8 10 12 14 16 18
Frequency [GHz]
Eff
icie
ncy
[%
]
Coaxial Horn
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
• adjustable phase center
• more than 30% bandwidth in
the lower frequency band
• more than 40% bandwidth in
the upper frequency band
Coaxial Horn, 3D Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
2 GHz 8 GHz
• very good pattern symmetry
• low crosspolarization
• coincidence phase centers for the two frequency bands
Coaxial Horn, Polar Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
Eleven-Feed, f = 2.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
10
0 [dBi]
5
-5
-10
-15
phi = 0°
phi = 45°
phi = 90°
Subreflector Rim
Mainreflector Rim
10
Eleven-Feed, f = 8.0 GHz0
30
60
90
120
150
180
-150
-120
-90
-60
-30
• low spillover
• constant illumination efficiency in both frequency bands
13.2m TTW Antenna Radiation Patterns
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
13.2m Ring Focus Antenna with Coaxial Waveguide Feed
f = 2.0 GHz, without VSWR Efficiency and Strut-Blockage
0
5
10
15
20
25
30
35
40
45
50
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Angle [deg]
Gain
[d
Bi] 90°_Co
0°_Co
45°_Co
45°_Cr
13.2m Ring Focus Antenna with Coaxial Feed
f = 8.0 GHz, without VSWR-Efficiency and Strut-Blockage
0
10
20
30
40
50
60
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
Angle [deg]
Gain
[d
Bi]
90°_Co
0°_Co
45°_Co
45°_Cr
13.2m TTW Antenna Efficiency with Coaxial Horn
(without VSWR and Strut Blockage Efficiency)
0
10
20
30
40
50
60
70
80
0 2 4 6 8 10 12 14 16 18
Frequency [GHz]
Eff
icie
ncy
[%
]
• high efficiency in both frequency bands
• low crosspolarization
Multiband Corrugated Horn
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
Corrugated Horn Gain
Semi Flare Angles 10.0°, 12.5°,15.0°, 17.5° and 20.0°
5
7.5
10
12.5
15
17.5
20
22.5
25
27.5
30
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Aperture Diameter Wavelength
Ga
in (
dB
i)
10.0°
12.5°
15.0°
17.5°
20.0°
Bandwidths for Allowable Groove Depth
0
5
10
15
20
25
30
35
40
45
50
55
60
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Frequency (GHz)
All
ow
ab
le G
roo
ve
De
pth
(m
m)
1/4 Lambda
1/2 Lambda
3/4 Lambda
1 Lambda
1 1/4 Lambda
1 1/2Lambda
1 3/4 Lambda
2 Lambda
2 1/4 Lambda
2 1/2 Lambda
2 3/4 Lambda
3 Lambda
Exclusion
Exclusion
Exclusion
Exclusion
Exclusion
Exclusion
• generally, a corrugated horn can
achieve a 2:1 frequency bandwidth
• if the corrugation depth is an odd
multiple of a quarter wavelength, the
horn geometry will work
• when the corrugation depth approaches
half of the wavelength, or multiples of it,
the horn pattern will breakdown
• not every frequency combination is
realizable
Multiband Corrugated Horn
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
The conical or tapered form of a corrugated horn is a natural frequency filter.
The frequency bandwith of a coupling junction is limited to a bandwith of about
10%.
Conclusion
MIRAD Microwave AG Broadband Feedsystems IVS VLBI2010 Workshop March 2009
13.2m TTW Antenna Efficiency Eleven Feed, Quadridge Horn and Coaxial Horn
(without VSWR and Strut Blockage Efficiency)
0
10
20
30
40
50
60
70
80
90
0 2 4 6 8 10 12 14 16 18
Frequency [GHz]
Eff
icie
nc
y [
%]
Eleven Feed
Coaxial Horn
Quadridge Horn
If the frequency
bandwidth is needed, the
Eleven feed is the best
approach.
With coaxial feeds or
multiband corrugated
horns better antenna
performances is possible
in limited frequency
bands.