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LTE’s MIMO Requirement Strengthens the Need for Active Antenna Systems

Jeff ShamblinChief Scientist

December 2013

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• Leading embedded antenna system provider for wireless devices

• Global customers: mobile phones, notebooks, consumer devices, enterprise devices

• 1,000+ platform design experience

• One billion embedded antennas shipped• 7M units per week run-rate• Strong design-win portfolio• Steady growth and profitability

• Global design centers, experienced team• Taiwan, China, Korea, Europe, US• Close to major wireless customers’ design teams• 200+ employees, 80% engineering

• Several awards recognizing growth and innovation

Ethertronics Company Profile

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Agenda

• Benefits of implementing Active Antenna Techniques• 4G provides a strong motivation to move to active antennas

• Bandwidth/Efficiency/Volume Tradeoff• Size limitations for the antenna determined

• Active Antenna Techniques• Case study 1: Adaptive Impedance Matching• Case Study 2: Band Switching or Active Aperture Technique• Case Study 3: Combination of Adaptive Matching and Band Switching for best performance• Case Study 4: “Air InteRFace ProcessingTM” Beam Steering for improved connectivity

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Why Implement Adaptive Antenna Techniques?

• The frequency bands required from the main antenna are expanding• Issue prevalent in cell phone, laptop, and other wireless devices

• 4G is a MIMO protocol requiring a 2 antenna solution in the mobile device• Envelope correlation and isolation between antenna pair are important

• Must consider and compensate for detuning of antenna system due to body loading

• SAR is and will continue to be an important and difficult requirement to satisfy

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Why Implement Adaptive Antenna Techniques?

• Five antennas being designed into the typical smartphone today• Main, Secondary, GPS, Wifi, NFC

• Available volume for antenna system is decreasing and current trend is for a thin device

• Screen and battery continuing to dominate internal volume of smartphone

NFC

Typical smartphone

Antenna layout in smartphone

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Available Volume for Antenna System is an Issue

• A survey of current smartphones on the market reveals:

Galaxy S3 iPhone 5 Lumia 920 HTC One X Droid Razr M

Smartphone volume cm3 83 55 99 84 62

Smartphone thickness mm 8.6 7.6 10.7 8.9 8.3

Smartphone volume cm3 70.4

Display volume cm3 16.6

Battery volume cm3 17.7

Plastics 14

PCB, populated 7.6

Camera, connectors, speaker 6

Antenna System 8.5

Case Study

5 antennas integrated into this volume!!

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Agenda

• Benefits of implementing Active Antenna Techniques• 4G provides a strong motivation to move to active antennas

• Bandwidth/Efficiency/Volume Tradeoff• Size limitations for the antenna determined

• Active Antenna Techniques• Case study 1: Adaptive Impedance Matching• Case Study 2: Band Switching or Active Aperture Technique• Case Study 3: Combination of Adaptive Matching and Band Switching for best performance• Case Study 4: “Air InteRFace ProcessingTM” Beam Steering for improved connectivity

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Antenna Efficiency Considerations Related to VolumeAntenna efficiency is dictated by many factors:

Available volume that the antenna occupies

Bandwidth required

Frequency of operation

Material and matching component losses

Theoretical analyses, such as the analysis performed by Wheeler provide a measure of bandwidth that is achievable for a set volume. This analysis assumes efficient propagation, so it provides information related to achievable bandwidth but little insight into the efficiency that can be achieved when attempting to increase bandwidth performance from a set volume. Measured efficiency data can be used to determine efficiency for fixed volumes

The following slides show measured efficiency data for four antennas of various volumes tested in similar environments

A brief description of bandwidth that can be achieved for a fixed volume is also included

From this efficiency/bandwidth study the trends are

A larger volume is required for the antenna as the frequency decreases for a fixed bandwidth if efficiency is to be maintained

Higher frequencies (1700MHz and greater for the volumes studied) will have good efficiency and bandwidth characteristics; for active antennas tuning can be constrained to the lower frequency bands, i.e. less than 1GHz

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3wavelengthradiovolumeemodantennaK

ff

Dimensionless constant K is usually 50-100

The basic equation for small antennas:

FCC allocated Band

Center Frequency

Band-width Effective Antenna Mode Volume

(Volume)1/3

LTE 750MHz 50MHz 43 cm3 3.5 cm3

Cell-phone 859MHz 70MHz 35 cm3 3.3 cm

GPS 1575MHz 10MHz * 0.44 cm3 0.76 cm

PCS 1920MHz 140MHz 2.8 cm3 1.4 cm

Bluetooth 2440MHz 80MHz 0.60 cm3 0.85 cm

* Actual GPS bandwidth is 2MHz, practical bandwidth needs to be 10MHz to allow for tolerances. All volumes based on K100

Antenna Volume Requirements

Wheeler’s formula shows that the bandwidth ∆f over the central frequency f is linked by a dimensionless number K to the ratio of the antenna mode volume to the wavelength

o The K factor is related to the antenna technology and how it is designed

Translation: Higher frequencies (2 to 3GHz) are easier to implement than 700MHz LTEo Smaller volume requirement enables higher isolation, low pattern correlation in well designed antennas

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Antenna Mode Volume Required for Fixed Bandwidth

0

10

20

30

40

50

60

70

80

600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600

Ant

enna

Mod

e Vo

lum

e (c

u. c

m)

freq (MHz)

Antenna Mode Volume Required for Fixed Bandwidth

460 MHz Bandwidth

140 MHz Bandwidth

70 MHz Bandwidth

35 MHz Bandwidth

GSM850/EGSM

GSM850 only

DCS/PCS/WCDMA

LTE 700 band42 MHz

This graph shows lines of constant bandwidth; for a fixed bandwidth, frequency of operation along the x-axis can be related to antenna mode volume required, along the y-axis

As the frequency of operation decreases and/or bandwidth requirement increases, more volume will be required for efficient operation

3wavelengthradiovolumeemodantennaK

ff

Wheeler’s formula

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Efficiency/Volume Tradeoff: Free Space

Measured data for four antennas is shown belowThe four antennas represent an approximately doubling in volume from one size to the nextThe tabulated data displays low band and high band efficiency for the four antennas0.9, 1.8, and 3.1cm3 are active antennas; 6.3cm3 is a passive antenna

Low Band Ave.Efficiency (%)698 – 960 MHz

High Band Ave. Efficiency (%)1710 – 2690 MHz

0.9 cm3 29 44

1.8 cm3 50 56

3.1 cm3 55 58

6.3 cm3 63 50

Low band efficiency most affected by volume reduction

70mm by 130mm PCB for active antennas

50mm by 115mm PCB for passive antenna

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Agenda

• Benefits of implementing Active Antenna Techniques• 4G provides a strong motivation to move to active antennas

• Bandwidth/Efficiency/Volume Tradeoff• Size limitations for the antenna determined

• Active Antenna Techniques• Case study 1: Adaptive Impedance Matching• Case Study 2: Band Switching or Active Aperture Technique• Case Study 3: Combination of Adaptive Matching and Band Switching for best performance• Case Study 4: “Air InteRFace ProcessingTM” Beam Steering for improved connectivity

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Multiple Active Antenna Techniques Are Available

• Feed point tuning of an antenna is only part of the optimization that can occur when developing an adaptive antenna system

• Open Loop Active Matching Techniques: Active matching circuit applied to an antenna utilizing a look-up table or external control signals in an open loop architecture; improves frequency bandwidth

• Closed Loop Active Matching Techniques: Active matching circuit applied to an antenna in a closed loop architecture to provide dynamic compensation for de-tuning affects such as changes to the local environment (body loading for example); more optimal solution compared to open loop solution

• Band Switching Technique: Electrical length of radiating aperture is altered dynamically to better optimize the radiated efficiency over a wider frequency range; improves frequency bandwidth

• Beam Steering Technique: Dynamically altering the radiation pattern of an antenna to better optimize the antenna for the multi-path environment; results in improved throughput

• One or a combination of these techniques adjust the three key parameters of an antenna: 1) Impedance2) Efficiency/Bandwidth characteristics3) Radiation pattern characteristics (shape, polarization)

Resulting in Improved throughput, QOS, power saving

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3 Active Antenna Techniques for Improved Performance•The antenna has dual functions: • The antenna is a circuit element with impedance properties that interfaces with the front-end• The antenna is an EM radiator with radiation pattern and polarization characteristics that

interfaces with the propagation channel

Active Matching(active matching circuit)

Null Steering

(radiation pattern control)

0 0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.2

1.4

1.6

1.8

2.0

3.0

4.0

5.0

10 20

1.0

50

1.0

50

Switched Antenna

(frequency shift)

• Open and closed loop adaptive matching techniques will only address the impedance properties of the antenna

• Develop and implement Adaptive Antenna techniques to

• Dynamically adjust impedance properties of the antenna

• Dynamically adjust frequency of the radiator • Dynamically optimize radiation pattern

characteristics

RFFront-end

Propagation channel

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Case Study 1: Adaptive Matching Applied for Band Switching and Compensation of Body Loading•Adaptive Matching technique can be implemented to • Band switch a main antenna• Compensate for body loading (“head and hand” effects)

•Adaptive antenna configuration can be implemented utilizing• Antenna element• Tunable capacitor• Passive matching components (capacitors and inductors)• Look-up table with tuning data• Link to baseband required for frequency band information and proximity sensor response

Baseband

Look-up Table

Ctrl signal

Adaptive Matched Antenna

RF TunableMatchingcircuit

Frequency band statusOther stimulus

RFFE

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Case Study 1: Adaptive Matching Applied for Band Switching and Compensation of Body Loading• Adaptive Matching solution developed as a system (antenna element, tunable matching

circuit, look-up table) to cover the frequency range of interest and loading states

Hx00

Hx08

Hx0F

Hx18

Hx1D

Q = 1

Q = 2

Q = 3

f0 = 908MHzf0 = 856MHz

f = 800MHz f = 960MHz

BW = 160MHz

- 6dB

Hx00

Hx08

Hx0F

Hx18

Hx1D

Antenna element and matching circuit optimized for Bands 5, 6, and 8

Antenna element and tuning component designed to cover frequency range of interest and loading conditions

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Case Study 1: Compensate for Hand Effect• Frequency response of antenna is centered for “Free

Space” condition• “Hand Loading” of cell phone causes a downward shift in

antenna frequency response• Tunable capacitor used to shift frequency response

Free space

Right Hand effect

Right Hand + Head effect

Hx00

Hx08

Hx0F

Hx18

Hx1D

Hx00

Hx08

Hx0F

Hx18

Hx1D

Hx00

Hx08

Hx0F

Hx18

Hx1D

Frequency band of interest

Frequency band of interest

824 – 894 MHz (Bands 5/6)

880 – 960 MHz (Band 8)

These capacitor tuning states compensate for Hand Loading

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Case Study 2: Band Switching Technique (Active Aperture) for Dynamic Frequency Control•Band Switching technique can be implemented to • Band switch a main antenna• Technique provides improved efficiency as frequency is adjusted

•Adaptive antenna configuration can be implemented utilizing• Antenna element• Multi-port switch• Passive matching components (capacitors and inductors)• Look-up table with tuning data• Link to baseband required for frequency band information

Baseband

Look-up Table

Ctrl signal

Band Switching Antenna

RF

Switchmodule

Frequency band statusOther stimulus

RFFE

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Case Study 2: Band Switching Technique

• Band switching technique implemented to adjust electrical length of radiating element• 4 tuning states for covering lower bands, 698 – 960MHz• Full instantaneous bandwidth across upper frequency bands, 1710 – 3000MHz

High band radiating element

Low band radiating element

S1 S4S2 S3

I/P1

I/P2

I/P3

I/P4

Antenna feed point

Switch assembly

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Case Study 2: Performance Data

• Efficiency of 4 tuning states• Optimum efficiency derived from 4 tuning states• Efficiency in dB, Cable loss included

Low band response covered in 4 states1. 698-MHz to 747-MHz2. 746-MHz to 798-MHz3. 824-MHz to 894-MHz4. 880-MHz to 960-MHz

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Case Study 3: Adaptive Matching and Band Switching Applied to Antenna

Baseband

Look-up Table

Ctrl signals

Adaptive Matching and Band Switching Antenna

RF

Frequency band statusOther stimulus

RFFE

•Adaptive Matching and Band Switching technique applied • Optimal approach• Both impedance and frequency response can be dynamically controlled

•Coarse and fine frequency tuning of frequency response• Antenna element• Antenna Tuning Module (ATM)• Passive matching components (capacitors and inductors)• Look-up table with tuning data• Link to baseband required for frequency band information

AntennaTuningModule

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Case 3: Active Antenna Concept

• Active antenna concept developed that provides coarse frequency adjustment (Band Switching) and fine frequency adjustment (tunable matching circuit) in a small form factor design

• The active antenna occupies 1.78cm3 has been developed to cover 2G/3G/4G frequency bands

• The antenna has been designed to provide tunability across the lower frequency bands (698 – 960MHz) and full upper frequency band coverage (1710 – 2690MHz)

• The tuning states at the lower frequencies are:• State 1: Bands 17/14 (698‐746MHz)

• State 2: Bands 13/20 (746‐861MHz)

• State 3: 850GSM (824‐894MHz)

• State 4: EGSM900 (880‐960MHz)

Antenna dimensions: 48mm x 7.4mm x 5mmAntenna volume: 1.78cm3

Board dimensions: 70mm x 130mm8mm ground plane removed

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Case 3: Return Loss, Free Space

• Four tuning states provide coverage from 698 to 960MHz• All four low band tuning states provide full upper frequency coverage

Antenna dimensions: 48mm x 7.4mm x 5mmAntenna volume: 1.78cm3

Board dimensions: 70mm x 130mm8mm ground plane removed

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Case 3: Antenna Efficiency at Low Band, Free Space

• Minimum 40% efficiency achieved at all frequency bands

Freq Band

Ave. Efficiency (%)

Bands 12/17

43

Bands 13/20

50

GSM 50

EGSM 48

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Case 3: Antenna Efficiency at High Band, Free Space

Freq Band

Ave. Efficiency (%)

Bands 12/17

53

Bands 13/20

56

GSM 58

EGSM 56

• Average efficiencies shown at high band frequencies for the 4 tuning states

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Base station A

Base station B

Base station C

• Dynamically alter the radiation pattern to better optimize for the propagation channel

• Sample and switch between base stations for best connection and fastest throughput

• Applicable to fringe networks

C

AB

mobile C

A

B

mobile

Case Study 4: Beam Steering or Radiation Pattern Altering Techniques

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A Differentiating Technology

• Ethertronics has refined a technique to effectively Beam Steer in a handset

• This technology advancement has broad implications in terms of improved handset performance in a cellular network

• This active antenna system technique is designed to match the antenna characteristics to the propagation channel, providing an improved connection to the network

• This Beam Steering technique is called Air InteRFace Processing SystemTM

• Air InteRFace Processing System provides • Higher data rates at the handset• Increased network capacity by efficiently off-loading users to adjacent cells• Increased battery life due to improved upload and download performance• A viable SAR reduction technique

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Air InteRFace Processing SystemTM

• Addresses wireless issues such as: capacity, emissions, device size, power consumption and SAR management

• A single antenna and RF functioning as multiple antennas; applies to MIMO• Algorithms to optimize performance of applications

An innovative approach for solving many issues in wireless

Changing the radiation pattern and controlling itDepending on applications single antenna with multiple patterns

A Unique Technology

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Air InteRFace Processing System

Algorithm

Front-end

• Air InteRFace Processing System consists of:• Null Steering Antenna• RFIC tuning module• Algorithm

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Mode 1 of the antenna provides alink with Base Station A which is marginal

Base Station A

Base Station B

Base Station C

How to Visualize Air InteRFace Processing

Capacity =M * B * Log2(1+S/N)

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Mode 2 of the antenna provides a linkwith Base Station A which improves by several dB

Base Station A

Base Station B

Base Station C

How to Visualize Air InteRFace Processing

Capacity =M * B * Log2(1+S/N)

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In some cases depending on the orientation and the Propagation between mobile and Base Station A, B, C, we will switch to a better BT to optimize the QOS..could be the case for fringing areasBase Station A

Base Station B

Base Station C

C

AB

mobile

How to Visualize Air InteRFace Processing

Capacity =M * B * Log2(1+S/N) AB

C

33Base Station A

Base Station B

Base Station C

C

AB

mobile

How to Visualize Air InteRFace Processing

Capacity =M * B * Log2(1+S/N)C

AB

mobile

AB

C

In some cases depending on the orientation and the Propagation between mobile and base station A, B, C, we will switch to a better BT to optimize the QOS..could be the case for fringing areas

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Air InteRFace Processing System consists of three parts:

1) Null Steering antenna

2) RFIC tuning Module

3) Algorithm

The Two Components of Air InteRFace Processing

Multiple Radiation Patterns

Air InteRFace Processing System

Ctrl Signals

Baseband RFIC

Algorithm

Null SteeringTM

Antenna

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Air InteRFace Processing System provides multiple radiation patterns from a single antenna structure

Dynamically Optimize the Radiation Pattern for the Propagation Channel

Multiple radiation patternsAir InteRFace Processing System

Ctrl Signal

Fixed radiation patternTypical passive antenna

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Air InteRFace Processing System Test Bed

• Demonstrated 4 unique radiation patterns in a Qualcomm FFA Test Phone in 2011

• 1900 and 2100MHz bands (Bands 1 and 2)• 0.2cm3 antenna

• 6dB SINR improvement compared to single antenna solution for receive diversity application

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A More Comprehensive Approach

Dynamically adjust impedance of the antennaDynamically adjust frequency of the radiator Dynamically optimize radiation pattern

Baseband

Ctrl signal

Adaptive Antenna System

RFAntennaTuningModule

- Frequency band status- CQI- Proximity sensor status

Processor

• One antenna structure• One chipset or module to tune and optimize antenna characteristics• One set of control signals from Baseband to implement multiple antenna optimization

functions

RFFE

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Conclusion

•Adaptive antenna techniques should address and optimize multiple parameters of an antenna system:

1) Impedance properties

2) Efficiency/Bandwidth characteristics

3) Radiation pattern characteristics (shape, polarization)

•Combining adaptive techniques brings more capability to the antenna• Dynamically adjust impedance• Match antenna radiation pattern to the propagation channel• Dynamically optimize the radiator to the frequency band of interest

More bandwidth in same volume

Smaller size withsimilar performance

Offsetting head,hand and body effects

Faster time to market for antenna solution

Improved spec compliance across bands