Phased-Arrays in Radio Communication Systems

Prof. dr. ir. Bart Smolders

NXP Semiconductors, Nijmegen, The Netherlands

Eindhoven University of Technology (TU/e)

2

Content

Trends in wireless communication systems

Examples of Phased-arrays in Communications– Cellular communication infrastructure– Satellite Reception and two-way communication– mm-Wave applications and Antenna-on-Chip

Conclusions

3

Trend 1: Increase in bandwidth:Edholm’s LawFrom IEEE spectrum July 2004

Required Bandwidth/datarate doubles each 18 months

- Wireless growing faster than wired

-7 GHz available at 60 GHz

4

Trend 2: Increase of operational frequency

1900 1920 1940 1960 1980 2000 202010

-3

10-2

10-1

100

101

102

Year

Freq

uenc

y [G

Hz]

Frequency vers us year of introduction

TVGSM

Satellite TV

AM

FM

Car radar

60 GHzWLAN

- Relative BW- Availability of new

bands- Next step sub-THz?

5

Trend 3: Increase in power consumptionNeed for high-efficiency technologies

+12.500 windmills +50 conventional power plants

OR

Without changes only for cellular basestations we would need in the next 10-15 years:

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In Summary

Edholm’s law drives towards higher datarates– Shift to higher frequencies due to more absolute BW– Need for more efficient use of the available spectrum.

Phased-arrays can offer a solution here– Higher frequencies will require a high Antenna Gain and

electronic beam steering– Smart beamforming techniques offer higher datarates and

more frequency re-use.

But,– Communication systems require low cost.– Need for highly integrated solutions using Silicon-based IC

processes.

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Phased-arrays in cellular communication infrastructure

8© The International Engineering Consortium

Cellular Communication Infrastructure

9

Cellular Communication Infrastructure

© The International Engineering Consortium

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Cellular Communication Infrastructure

11

Cellular Communication Infrastructure

12

Security fence

Equipment shelter

3G antennas

Electricity supply

Access road

2G antennas

Coaxial feeder cables

Point to point radio backhaul antenna

Backhaul cable

BTS (2G) Node B (3G)

Cell site efficiency =

< 4%

PRF

PDC

W-CDMA cell site efficiency

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|a1|exp(-jφ1) |a2|exp(-jφ2) |aK-1|exp(-jφK-1) |aK|exp(-jφK)

SUMMING NETWORK

S

s1 s2 sK-1 sK

z

WAVE FRONT

dx dx

Antennaelement

θ0

d xsinθ 0

1 2 K-1 K

Phased Array Concept

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Multiple beams and beamsteering

• Phased Arrays use multiple steered beams to eliminate fading effects.• Effective antenna gain depends on number of instantaneous users and their location.

• Beam steering requires lower output power, thereby saving energy.

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AC/DCConverter

Pin

220V85% 85%

DC/DCConverter

Idle48%

30%

PALow Power RF

DSPMicrowave linkBattery backup

Typical power balance without Phased-arrays

Pout

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AC/DCConverter

220V -48V +27V85% 85%

DC/DCConverter

Idle48%

30%

Example: Beam Steering with 6 dB extra average antenna gain: consumes 70 W iso 250 W for single antenna.

PALow Power RF

DSPMicrowave linkBattery backup

Beam steering antenna

Typical power balance with Phased Arrays

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Design basisstations with phased-arraysArtist impression Ericsson

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Phased-arrays in Satellite reception

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Current situation

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Drive for innovation in antenna concepts

Less “visible” antennas, especially in urban areas

Multi-beam requirements, reception of multiple satellite positions simultaneously.

Interference suppression by using beam-nulling techniques.

Most promising (low-cost) concepts:– Focal-plane arrays– Reflect-arrays

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-5 -4 -3 -2 -1 0 1 2 3 4 5-25

-20

-15

-10

-5

0

θ [deg]

Nor

mal

ised

arra

y pa

ttern

[dB

]

Modified pattern with interference nulling at +/- 2 degrees , f=11 GHz

Focal-plane Array for interference suppressionExample of reflector antenna with 3 feeds

Sat 1 Sat 3Sat 2

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ASTRA satellites and services

Orbital Position Satellite Use

50 E ASTRA 4AASTRA 1C

DTH services to Nordic countries and the Baltic, Eastern Europe, Ukraine, Russia.

19.20 E ASTRA 1FASTRA 1GASTRA 1H

ASTRA 1KRASTRA 1LASTRA 1M

DTH services to large audiences markets, e.g. Germany, France, Spain.

23.50 E ASTRA 3AASTRA 1E

DTH services for dynamic markets, e.g. Italy, Benelux, Central and Eastern Europe.ASTRA2Connect – Broadband Internet and

VoIP.

28.20 E ASTRA 2AASTRA 2BASTRA 2CASTRA 2D

DTH services to UK and Ireland.

31.50 E ASTRA 1D Cable TV distribution, Digital Terrestrial TV (DTT) and other terrestrial feeds

throughout Europe.

16 Satellites – 5 Orbital Positions

Specifications

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Reflect arrayLow-cost solution for multi-beam/beamsteering

A Ku-band demonstrator for Satellite DVB-TV was developed at the TU/e, using fixed beams

Next step to include MEMS phase-shifter for dynamic beam steering

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Reflect array, element design using low-cost patch antennas

Aperture Coupled Microstrip Antennas (ACMA)

• High Bandwidth• Space for microstrip line• Many degrees of freedom

Microstrip stub-length determinesphase-shift.

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Reflect array prototype, Antenna patterns

-80 -60 -40 -20 0 20 40 60 80-20

-10

0

10

20

30

40

50

X: 1Y: 35.49

X: 5.5Y: 35.42

X: -13.5Y: 33.9

X: 10Y: 35.19

THETA (degrees )

X: 13.5Y: 35.15

GAIN

(dB)

5 degrees19.2 degrees23.5 degrees28.2 degrees 31.5 degrees

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Phased-arrays in mm-wave applications

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Background-60GHz Applications

PAGE 272009-4-22

Source: IBM

• Need high-Gain antennas for link-budget• LOS communication, Need beam-steering

• 6 GHz Bandwidth• 2-10+ Gbps datarate

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1990 1995 2000 2005 2010 2015 202010

100

1000

Year

Tran

sit F

requ

ency

[GH

z]

RFCMOS SiGe BiCMOS

Ft of IC Technology vs Year [ITRS] & applications

Sat TV

24 GHzCar radar

60 GHzWLAN

77 GHzCar radar

94 GHzImaging

f T=2*f app

f T=10*f app

NXPQubic4Xi

ITRS= International Technology Roadmap for Semiconductors

20~30 GHzPoint to point

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How small can we make an antenna?Chu-Harrington fundamental limit

10-2

10-1

100

10-6

10-5

10-4

10-3

10-2

10-1

100

101

antenna s ize kr

Max

imum

Ban

dWid

th E

ffici

ency

pro

duct

Chu-Harrington fundamental limit of s mall antennas , BW*Eff

limit Dipole Goubau 1976 P atch S molders

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Cost of Antenna-on-Chip (AoC)

10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

Frequency [GHz]

Pric

e ad

der [

Eur

o ct

]

Antenna-on-chip P rice adder [Euro ct] vers us frequency

Normal Dipole BW=10% S mall antenna BW=0.2%

+ Lower test cost+ Lower package cost

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Silicon (Bi-)CMOS Technology stackTypical example

PAGE 312009-4-22

RV

AP

MZ

Substrate resistivity 15Ω.cm

ViaZ

Viax

POLY

M1

Mx

CO

• Typical 6-8 Metal layers• Thick metal 1-3 μm (top layers)• Substrate Res 10-200 Ohmcm• Wafer thickness 20-300 μm• Substrate modes are main issue

to address for efficiency and mutualcoupling

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60 GHz AoC prototype in Qubic4Xi technologyOverall Gain ~ 0 dBi

4.5 5 5.5 6 6.5 7

x 1010

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

frequency [Hz]S

11 [d

B]

Measured return loss

Advantages: - Reduced package, test and application cost- Higher performance due to direct matching antenna and electronics

1.5 mm

Paper accepted for publication at APS 2009

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Example of 4x1 integrated array in BiCMOS77 GHz 4x1 phased array transceiver with integrated antennas

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1. Edholms law drives towards more efficient use of available bandwidth and leads towards higher frequencies.

2. Phased-arrays will be needed in upcoming years.

3. Low-cost Silicon implementations will boost phased-arrays.

4. Examples have been presented:

• Cellular basestations,

• Satellite reception/two-way communications,

• AoC and AnoC for mm-wave applications.

5. It will take 5-10 years before phased-arrays will be high-volume technology in commercial radio applications.

Conclusions

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Thank You

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