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Multi-Band Base Station AntennasAntenna Systems 2015 ◦ November 5-6 ◦ Las Vegas, NV
Igor Timofeev
Senior Principal Engineer
2© 2015 CommScope, Inc
Agenda
• Introduction to Multi-Band (MB) Antennas
– History, Evolution, and Challenges
• Part 1 - Ways to Mitigate Performance Degradation
– Nesting, Cloaking, Filtering, and Choking
• Part 2 - Practical Examples of Multi-Band (MB) BSA
• Part 3 - Multi-Band/Multi-Beam (MBMB) BSA
– Butler Matrix, Luneburg lens, Cylindrical Lens
3© 2015 CommScope, Inc
Introduction to Multi-Band (MB) Antennas:
History, Evolution, and Challenges
4© 2015 CommScope, Inc
Zaslon radar: 64 L-band & 1700 X-band
radiators and phase shifters
S-300 radar:
10000+ radiators
of different bands
MIG31
https://en.wikipedia.org/wiki/Zaslon
Examples of traditional
multi-band phased arrays
(Late 70s)
• In contrast with radar systems,
BSA have fewer elements –
dozens, not thousands.
• Also, because of PIM
requirements, electronic phase
shifters cannot be employed –
only electromechanical PS are
used (with motors).
• Beam scanning/tilting is
performing in only one
(elevation) plane.
• In azimuth, BSA should have the
same beamwidth in all bands
(85, 65, 45⁰ are standard)
• CommScope is the world leader
in design and manufacturing of
Multi-Broad Band (MBB) BSA.
BSA are different from Traditional MB Phased Arrays
5© 2015 CommScope, Inc
BSA: Evolution from Narrow-Band to Multi-Broad Band (MBB)
4 ports: (2x 806-896MHz + 2x1.85-1.99GHz)
(~10% LB, ~10% HB), 2 motors inside
12 ports: (4x0.7-0.96 + 8x1.7-2.7GHz)
(33% LB, 45% HB), 6 motors inside
Y2015: 70% of BSA are MB or MBBY2000: 10% of BSA are MB
Instead of jungle on the roof,
there is jungle inside antenna
One multi-broadband BSA can replace
up to 12 single band antennas
700 MHz
800 MHz
PCS
AWS
2300 MHz
2600 MHz
Low band (LB)
(< 1 GHz)
High band (HB)
(> 1 GHz)
6© 2015 CommScope, Inc
Challenges of Multi-Broad Band (MBB) Antennas
Grating lobes / parasitic lobes Asymmetry of Az pattern (squint, F/B)
x x
Xx x
x x
Xx x
*http://www.commscope.com/uploadedFiles/CommScopecom/Resources/Downloads/Band_and_Block_North_America.zip
• Coupling / blockage between elements could cause pattern distortion and degradation of RL,
isolation and gain.
• MBB increases potential harmful PIM (PIM that falls in the receive band)
- AWS1/3 combined with 700 results in 3rd order PIM hits in the 700 band.
- Download CommScope PIM calculator (see link below*)
• The goal of MBB design is minimize these performance degradations.
7© 2015 CommScope, Inc
Part 1 - Ways to Mitigate Performance Degradation:
Nesting, Cloaking, Filtering, and Choking
8© 2015 CommScope, Inc
Nesting: HB is nested inside LBUS Patent 7283101, 7405710, 8674895, 7358922
• For all cases below, the goal is to obtain 65⁰ Az beam in all bands with minimal antenna width.
• With nesting, it is difficult to obtain UWB HB operation (1.7 – 2.2GHz is OK, 1.7 – 2.7 is challenging).
LB Microstrip Annular Ring (MAR)
LB MAR
LB circular-type folded dipole array
Box-type HB radiator
HB1 (1.7 -2.2GHz)
HB2 (2.5 -3.8GHz)
Directors are moving the
HB center of radiation
higher and shaping the HB
radiation pattern
9© 2015 CommScope, Inc
Filters / Chokes /Traps in LB dipole: Trade-off Between HB Performance and LB Return Loss
LB current
HB current
λ/4 chokes
Printed low-pass filter
Chokes/filters improve Az beam
stability across the band but could
degrade LB RL
10© 2015 CommScope, Inc
Cloaking of LB dipoleTrade-off Between HB cloaking and LB Return Loss
Dk=4.4Cu pattern
Prof. Andrea Alu, UTA
w/o covered free space
Test results of LB dipole
11© 2015 CommScope, Inc
Part 2 - Practical Examples of Multi-Band (MB)
Base Station Antenna (BSA)
12© 2015 CommScope, Inc
2-Band BSA with 85⁰ Az BeamwidthDBXRH-8585C-VTM (US Patent 7053852, 7639198)
Frequency Band, MHz 698–806 806–896 870–960 1710–1880 1850–1990 1920–2180
Gain, dBi 15.1 15.0 16.2 17.0 16.7 17.1
Beamwidth, Horizontal,
degrees89 83 84 79 82 85
Beamwidth, Vertical, degrees 8.5 7.6 7.3 4.7 4.4 4.2
Beam Tilt, degrees 0–11 0–11 0–11 0–6 0–6 0–6
USLS (First Lobe), dB 15 15 15 16 17 17
Front-to-Back Ratio at 180°,
dB30 28 28 29 29 29
CPR at Boresight, dB 25 22 21 20 20 20
CPR at Sector, dB 13 11 10 9 9 10
Isolation, dB 30 30 30 30 30 30
Isolation, Intersystem, dB 30 30 30 30 30 30
VSWR | Return Loss, dB 1.5 | 14.0 1.5 | 14.0 1.5 | 14.0 1.5 | 14.0 1.5 | 14.0 1.5 | 14.0
PIM, 3rd Order, 2 x 20 W, dBc -150 -150 -150 -150 -150 -150
Input Power per Port,
maximum, watts400 400 400 300 300 300
Polarization ±45° ±45° ±45° ±45° ±45° ±45°
Impedance 50 ohm 50 ohm 50 ohm 50 ohm 50 ohm 50 ohm
HB and LB elements are placed in one
layer to minimize mutual distortions
and achieve very stable Az beamwidth
over both wide frequency bands
LB element
13© 2015 CommScope, Inc
2-Band BSA with 45⁰ Az BeamwidthUS patent 8,508,424
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Sector power ratio < 3% in both bands
(SPR is the most important for LTE)
9xHB elements with 5 directors on each
LB elevation pattern, tilt 16⁰
LB azimuth pattern, tilt 16⁰
HB elevation pattern, tilt 10⁰
HB azimuth pattern, tilt 10⁰
14© 2015 CommScope, Inc
Tri-pole: Solution for LTE MBB BSAUS patent 9077070
690 – 960MHz “Elephant Ear” tri-pole
Currents’ distribution
RL, Iso and Az pattern, 790- 960MHz
790 – 960MHz tri-pole