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Bob Giometti

Vice President R&D and Engineering, SkyCross

[email protected]

New Antennas for Mobile Technology

Presented at the Antenna Systems Conference

December 12-13, 2013

Las Vegas, NV

a

Contents

1. Introduction

2. LTE-A and the Mobile Device Antenna

3. LTE-A: Impact on the Antenna System

a. Requirements

b. Carrier Aggregation

c. Drivers for Antenna Tuning

4. Enabling Technologies

a. Aperture Tuning

b. Tunable Match Network

c. Hybrid Approach

d. Co-location of antennas

e. Isolated Mode Antennas (iMAT)

- Beam Forming Application

5. Summary

Introduction

3

- Over 20 years experience in the wireless industry

- Mobile phone product development at Motorola/Google

- Electrical design lead for the original RAZR

- BSEE/MSEE Illinois Institute of Technology

- Joined SkyCross as VP of R&D and Engineering Jan. 2013

Background/Bio

LTE- A and the Mobile

Device Antenna

5

• Many bands (40+ and counting….)– 700 MHz in US (sub-bands for AT&T and Verizon) – AWS (2.1/1.7 GHz) in US – 790-862 MHz in Europe– 2.6 GHz FDD – mainly in Europe– 2.6 GHz TDD – China, Europe– 2.3 GHz TDD – China, Korea, India– 600MHz on the way!

• GPS, BT, FM, NFC,…

• WiFi (Dual Band)

• Tx Diversity

• MIMO 2x2, 3x3, 4x4,…

• Carrier Aggregation– Low/Low, Low/High, High/High

LTE-A: Squeezing Even More Into The Mobile Device

Challenges facing today’s Mobile Device Antenna Engineer

Traditional antenna performance is inadequate to meet market demands for:

Increasing number of frequency bands (4G/LTE)

Increased data traffic clogged networks

Real life use cases (head, hand, slider phone)

Thinner phones Smaller antennas Quality of Service challenges

Bands of Interest vary by: Country / Region Network provider Protocol Use case

Need for advanced adaptiveantenna/RF solutions

“Advanced Smart Antennas” provide improved RF

Performance & Increased Flexibility

Fewer Dropped or

Missed Calls

Greater Cell Site

Area Coverage

~ Fewer cell sites;

~ Better spectrum utilization

~ Reduced Infrastructure costs

Faster Data Rates

Faster Time To Market

~ More Predictable Results

~ Fewer SKU’s

Thinner, More Stylish Phones

Reduced Power Consumption

~ Increased battery life

LTE-A: Impact on the

Antenna System

9

Enables more users, more applications,

and a better experience

Source: Rysavy Research/4G Americas, 2012

LTE 2010 to 2012

•5 or 10 MHz Radio Channels

•2X2 Multiple Input Multiple

Output (MIMO)

LTE- A 2013 to 2016

Higher Capacity/Throughput and/or Efficiency

•Wider Radio Channels: 20 MHz

•Carrier Aggregation: up to 100 MHz

•Advanced Antenna Configurations

•More Advanced MIMO (Higher Order, Multi-User,

Higher Mobility)

•Coordinated Multipoint Transmission

•Het-nets (Microcells/Picocells/Femtocells)

• Easiest way to arrange aggregation: use contiguous component carriers

within the same operating frequency band (as defined for LTE), so called

intra-band contiguous.

• May not always be possible, due to frequency allocation scenarios.

• For non-contiguous allocation it could either be intra-band, i.e. the component

carriers belong to the same operating frequency band, but are separated by a

frequency gap, or it could be inter-band, in which case the component carriers

belong to different operating frequency bands.

Carrier Aggregation Considerations

• LTE smartphones are challenged to achieve tightening carrier

performance expectations

– 4G LTE speeds/capacity require MIMO (multiple LTE antennas)

– Growing number of operating frequency bands (number of antennas)

– Aggressively styled device form-factors (constrained space)

• OEMs seeking new technical solutions to address challenges

– Tunable antenna solutions seen as the desired approach

– Progressive OEMs already initiating smartphone architectures that

support tunable antenna modules

• LTE-A Requirements

– Carrier Aggregation

– Higher Levels of MIMO

– Tx Diversity

LTE-A Drivers for Antenna Tunability

Enabling Technologies

13

Antenna Tuning Technologies

14

Tunable vs. Passive Antennas

• Integrates tuning elements,

antenna, and interface

• Smaller size (smaller than

conventional passive antennas at

same efficiency) or higher gain in

same size to reduce Tx power

consumption (increased battery

life)

• Separate from and

complementary to feed-point

impedance matching

• Supports Carrier Aggregation

requirements

• Primary/secondary antennas can

be co-located for greater space

reduction

• Potential to simplify filter circuits

• Simple 1 or 2 bit interface and

control

Motivation for Tunable Antennas

1. Greater band coverage +MIMO in accepted form factor allocated

space

2. Smaller Antenna: 1000 cubic millimeters or less (handset

OEMs)(need more tuning states)

3. Head/Hand Effect mitigation (requires sensor and algorithm)

(Operators)

4. Higher ASP stemming from integration of antenna and tuning

elements/control (Antenna Suppliers)

5. Lower VSWR (PA Suppliers)

6. Reduced Filter Requirements (Filter suppliers)

Aperture Tuning – Integrates tuning element, antenna,

and interface

– Antenna resonance is changed directly by the tuning element.

– Allows antenna to be made smaller or cover more bands than with passive antenna

– Simple interface and control to achieve open loop coverage on a band-by-band basis

– Often used with tuning devices such as switches or DTCs for open or closed loop control.

– Can be thought of as a “coarse tuner”

Tunable Matching Network – Used to improve VSWR match to

antenna.

– Not considered as producing optimal

radiation efficiency compared to

Aperture Tuning

– Improves power coupled to antenna

over frequency of operation and

under varying usage or

environmental conditions

– More complex interface generally

with 6 or more bits of control

– Can use analog tuning devices such

as BST and Varactor diodes, may be

open or closed loop

– Can be thought of as a “fine tuner”

Aperture Tuning (AT) vs. Tunable Matching Network (TMN)

Efficiency Comparison Between Passive Broad Band

and State-Tuned-Aperture Antennas

State 1

State 2

Broad Band

Low Bands High Bands

Significant improvement in low

band performance

>2 dB

Minimal impact to high band

performance

~0.8 dB

Aperture Tuning vs. Tunable Matching Network

Natural antenna/device bandwidth 824-960 MHz

TMN improves

efficiency at 750

MHz compared to no

match

3dB

delta TMN

Improves

match at

750 MHz

Aperture Tuning (AT) Advantage

Natural antenna/device bandwidth 824-960 MHz

AT match at 750 MHz has broader bandwidth vs. TMN

Hybrid Approach: Aperture + Match Tuning

RF

(Port 1)

Microcontroller

Control Algorithm

Flash

Memory

RF

(Port 2)

Tunable Matching Network

(Fine Tuner)

Optimize Performance

Diversity Aperture

Tuned Antenna

(Coarse Tuner)

Band Selection

MIPI RFFE GPIO Control

Tunable Matching Network

(Fine Tuner)

Optimize Performance

Diversity Aperture

Tuned Antenna

(Coarse Tuner)

Band Selection

Antenna Co-Location

22

Antenna Proximity Problem

• Far apart– Negligible coupling between

antennas

– spatial separation makes antenna patterns unique

– How far: generally more than about half wavelength (17 cm at 900 MHz) – size not feasible for many consumer products

• Close together - coupling between antennas may

be a problem (RX saturation or desense, TX distortion)

- coupling hurts radiation efficiency as power goes into neighboring antenna and not to far field

- patterns lose uniqueness and are highly correlated (loss of MIMO capacity or loss of diversity gain)

- Reality of many consumer products

Antenna starts to couple

more to its neighbor

than to the far-field

The MIMO Antenna Solution for 4G

: Isolated Mode Antenna Technology

• iMAT is a patented technology that allows a single antenna

structure to behave like multiple antennas through the use of

multiple feed points.

• Each feed point accesses the single antenna as if it consisted of 2, 3,

or more independent antennas that are highly isolated with superior

link performance gain.

• This compact solution is applicable to any mobile device! iMAT

supports legacy networks and is essential for next generation

protocols that require diversity or MIMO.

Patented Technology

Enables Multiple Antennas in Small Spaces

Antenna Requirements

• Diversity/MIMO

• High isolation

• High radiation efficiency

• Low correlation coefficient

• Small size

d

Conventional

Smart Antenna

Approach

Isola

tion d

B

0

-10

-20

-30Frequency

60

50

40

30

Effic

iency %

ISO

EFF

SkyCross iMAT

Solution

Isola

tion d

B

0

-10

-20

-30Frequency

60

50

40

30

Effic

iency %

ISO

EFF

1 2

The iMAT solution offers high efficiency, superior isolation, and low correlation coefficient

while maintaining equivalent return loss, with a single antenna!

Technology Applications

• WiFi and/or WiMAX

• 4G/LTE

• HSDPA / HSUPA

• 1XEVDO

• 802.11n, 802.11ac

• Mobile video (CMMB, T-DMB, DVB-H)

SkyCross Antenna

Technology

Breakthrough!

1 3 . . .3 . . .

d

2

iMAT Technology: Modal Interpretation

• The near fields are overlapping, but two unique antenna modes still exist

• In the simple case there are two resonant modes:– common mode: radiates similar to a lone

antenna would as the spacing becomes small

– differential mode: less effective antenna mode as the spacing decreases – the radiation resistance of this mode is diminishing as the antennas are brought closer

• Two physically separate antennas are not optimal in most cases – this system tends to utilize mostly one mode, the common mode

common

differential

Fundamental

Modes

iMAT: Far-Field Patterns

• Each resonance mode has a unique far field pattern

• With iMAT approach each antenna port couples to a different combination of the two fundamental modes

• The resulting far-field patterns are also unique to each other resulting in low ECC

Combination

- =

+ =

Pattern phase reversal

Farfield pattern

from Port 1

Farfield pattern

from Port 2

Common

Mode

Differential

Mode

iMAT: Concurrency of Isolation and ECC

• With iMAT Port-to-port isolation and low far-field correlation are obtained from the same design optimization at the same frequency

• Both result from the condition where the near fields associated with Port 1 are orthogonal from those associated with Port 2

• The proper conditions are achieved through resonance and so are inherently optimized to a particular frequency band or bands

Port-to-Port Coupling

Pattern Correlation

frequency

frequency

State 1 State 2

• Aperture tuning in SkyCross tunable antenna modules permits the actual radiating elements to be configured for optimal performance at each desired frequency band

• SkyCross ST-iMAT and Aperture Tuning deliver: Smaller size

Improved device performance

Network improvement (fewer dropped calls, increased network capacity)

Superior performance versus simple feed-point matching

SkyCross ST-iMAT™ (State-Tuned iMAT Antenna Module for Smartphone)

VersiTune-LTE™ Tunable Antenna Module

Smartphone

Implementation

iMAT

Radiating

Elements

Tunable

Antenna

Module

Tunable iMAT “Isolation Notch” Drives Multiband

Antenna Performance

iMAT design allows “control” of the isolation between ports. Drives higher efficiency and lower correlation coefficient

• Isolation is a measure of signal interference separation from one feed point to the other

• Correlation coefficient is the degree to which the two RF signals are distinct from each other

LTE-700 Corner to Corner

Conventional Antenna Design

VSWR: <2:1 Efficiency:

30-40%

CC:

>0.8Coupling:

-4dB

Patterns

almost

identical

iMAT LTE-700 Antenna Design

VSWR

<2.2:1

Isolation:

<-13 dB

Efficiency

50-58%

CC:

<0.35

Significantly

different

patterns

50x100mm

GP

iMAT Advantage vs. Dual Antenna: Correlation Coefficient

iMAT Antenna

PatternsDual Antenna

Patterns

Greater pattern diversity results in lower Correlation

Coefficient for iMAT vs. Dual Co-polarized Antenna

Independent analysis of iMAT vs. Conventional antenna for handsets shows iMAT

delivers significant improvement in Correlation Coefficient

Multiband Antenna Efficiency: ST-iMAT

State 1 State 2 State 3 State 4 State 5 State 6

Sin

gle

Po

rt O

nlyPrimary

Spec

Diversity

Spec

Measured Data: State Tuned iMAT configuration covering all LTE and Legacy 3G bands in 6 tuning states

• Phone chassis: ~58x120mm

• Modular Antenna: x=59mm, y=9.5mm (from display edge), z=3.7mm

Antenna volume (incl. keep out) = 2075mm3

Fully populated antenna module with speaker, microphone, USB3

Versitune-LTE Antenna Speaker Module Design Example

y =9.5mm

Antenna Elements

Flex PCB Antenna

(Double Sided FPCB)

Plastic Carrier

With Speaker Box

Embedded

Speaker

Audio Port

Microphone

USB Connector

Tuning

Components

Versitune-LTE Module Performance Summary

Key Features:

• Speaker, Microphone, USB connector and associated flex films integrated into assembly

• Vibrator, cameras an associated flex films in close proximity to the antenna

• Open Loop tuning with 3 tuning states for each low band: 17, 5, 8

• Supports CA for bands 4 & 17

VersitunePerformance Summary Simulations

Main TX Main Rx

Band & FreqEff

(dB)Goal delta

Eff(dB)

Goal delta

1 1920 - 1980 -2.7 NS -3.9 NS

2 1850 - 1910 -2.9 -3 0.1 -2.6 -6 3.4

4 1710 - 1755 -3.0 -3 0 -3.7 -4 0.3

5 824 - 849 -3.8 -4 0.3 -4.2 -5 0.8

8 880 – 915 -3.4 NS -3.7 NS

17 704 - 716 -3.8 -4 0.2 -4.4 -5 0.7

Free Space Cross Correlation Diversity RX

Band & Freq CC Goal deltaEff

(dB)Goal delta

1 2110 - 2170 0.0 NS -2.8 NS

2 1930 - 1990 0.0 0.5 -0.5 -5.7 -7 1.3

4 2110 - 2155 0.0 0.5 -0.5 -2.4 -7 4.6

5 869 - 894 0.3 0.5 -0.2 -8.0 -8 0

8 925 – 960 0.1 NS -8.1 NS

17 734 - 746 0.4 0.5 -0.1 -5.1 -8 2.9

Versitune LTE Efficiency - Primary/Secondary Port

Primary Port

Secondary Port

Performance data includes speaker, cameras, microphone, vibrator, micro USB

and associated flex interconnects in the antenna near field

Tuning

states 1,2,3

Versitune LTE Coupling (S12) - Primary/Secondary Port

Primary Port

Secondary Port



Versitune LTE - Envelope Correlation

Primary

Secondary



iMAT 2x2

Antenna

iMAT 2x2 Beam Forming Application

Antenna Beam Forming Problem for Handset Application

• Beam forming is accomplished by combining signals in two or more antennas at different phases

• For conventional antennas, as antenna separation decreases, the benefits of beam forming diminish due to the detrimental effects of antenna mutual coupling

• The separation between antennas, in terms of wavelength, is small for handset and mobile device applications (typically < 0.1 wavelength)

~

~

Antenna Array Combined Signal

Phase Shifter

s <0.1 wavelength at

cellular

frequencies

• A balanced iMAT design may be well suited for beam forming applications

• Both ports of iMAT antenna can be driven simultaneously

• Applying the same RF signal to both ports with a variable relative phase delay enables a beam forming solution

• Beam forming can provide 3 dB signal gain at the tower for same client device TRP

• Because there are two PAs,

each needs to provide only

half the total output power of the

traditional PA.

Port 1 Excitation

Ф

TX

PA

PA

iMAT antenna

Beam Forming – iMAT Technology

Beam Forming Application

Analysis Comparing iMAT to Conventional Antennas

Analysis Result – single iMAT antenna produces better beam forming gain than a pair of

conventional dipoles

Improvement due to iMAT

Summary

1. LTE-A requirements are driving the need for new,

more complex antenna technologies

2. Close attention to the antenna early in the design

stage is even more critical due to higher levels of

complexity

3. Antenna designs that may utilize a combination of

technologies can be used as a competitive

advantage that allows for product differentiation

This is truly an exciting time to be a

mobile device antenna designer!

THANK YOU!

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