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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